Conference vicki::boats

    Wayne, The marina that services my boat users a simular additive
    at the begining of the season as an octain boast for the fuel that
    sits over the winter. I"m not a beliver of the 15% increase in
    performance but it could smooth out the engine if your fuel octain
    is lower then your engin requires.
    BTW, I find Sept. and Oct great boating in Buzzards Bay esp. chasing
    Blues.
    
    George

    Wayne,
    If your motor is not knocking or pinging, I wouldn't bother trying
    to increase octane.  And unless a motor is pinging badly, claims
    of 15% more horsepower simply by increasing octane are ridiculous
    (IMO).
    
    Your motor is what, a 1964 Ford 260?  That's a fairly low compression
    motor and doesn't need lots of octane. What you *should* be concerned
    is replacing the lead that's missing from the fuel. Your motor does
    not have hardened valve seats, and without the lead to lubricate the
    seats, their life expectancy will be greatly reduced.
    
    Look for a product that claims to replace the lead by lubing the 
    valve seats.  As a side benefit, this product will probably also
    increase octane, but that's not your primary concern.
    
    Rick

    Rick, I am using a lead substitute already.  I believe that the engine
    has about an 8.8 - 1 compression ratio so pinging is not a problem when
    I use 93 Octane high test unleaded with the lead additive.  I just
    wanted to see if this stuff does anything of what it claims, not just
    stop pinging.
    Wayne

    
      Like Rick said, extra octane will not help you at ALL unless your
    motor *needs* it. From the specs of your motor, I highly doubt that it
    does. Remember, the octane rating ONLY refers to a fuel's ability to
    resist pinging, nothing else. A side benefit in *pump* high octane fuel
    is that the oil companies put more detergents, etc in it to help
    justify the price.
    
    				Kenny
    

    If there is no pinking (as it is called in England, not "pinging"),
    then your engine simply does not require increase in octane rating,
    furthermore any journal will tell you that increasing fuel octane can
    indeed *reduce* performace. The advertising companies bank on a
    psychological feeling of performance improvement for their miracle
    (read rubbish) products.

RE: .5
>> The advertising companies bank on a psychological feeling of 
>> performance improvement for their miracle (read rubbish) products.

Yep - I believe this is the same factor that always makes my cars run
better after a good wash, wax, and vacuum.  Anyone else ever notice that?

Just a minor nit - not all of these products are rubbish.  Some engines
actually DO require the increase octane or valve lubrication and most
of the products work as advertised.  The ripoff comes in selling the
stuff to customers who don't NEED it.  Later model marine engines, whether
inboard or outboard should be able to run fine on 89 octane pump gas with
no octane additives. Even the new 500+hp Mercruisers have low compression 
and don't require premium gas.

Rick

    So, with my 1978 25 HP Johnson the advice seems to be run premium ONLY
    if the engine needs it.  As I understand it one can't HEAR a 2 stroke
    outboard ping anyway so I can't really know if it needs it or not.  Since
    ping is so harmful to a 2 stroke its risky to run regular.  My
    conclusion is that its safer to run premium even if I don't need it.
    
    Jeff

    Re .7:
    
    If the manufacturer recommends 89 Octane, then that's what you should
    use, as the engine's lifecycle and operation are optimised for that
    octane. Anything else would have the overall effect of performance
    and/or life reduction, unless there are obvious signs to the contrary.
    
    Ray

    re: .8
    Choosing fuel for older motors isn't so cut and dried. The
    octane *rating system* was changed at some point, back in 
    the late 70's I think.  The 89 octane of the 1990's is not 
    the same as the 89 octane of the 1960's.  I said a while back
    that you should use the highest octane you can get or afford, 
    and was rebutted by a couple people who made a good case for
    why it could caused burned valves on a 4 cycle engine.
    
    Then you've got the issue of leaded gas not being available
    any longer for valve seat lubrication, while most older 4 cycle
    engines still need it.
    
    And unleaded gas, which was supposed to reduce deposits and
    emissions is now causing *increased* deposits (and stuck rings)
    when combined with the oil in 2 cycle engines.  This is supposedly
    due to reduced detergency, and not the lack of lead.
    
    Like feeding our bodies, things that you thought were good for
    you later turn out to be unhealthy after further study. No un-biased
    source seems to be able to tell you with any authority what the 
    perfect combination of fuel, 2 cycle oil, and aftermarket additives 
    are for your boat.  I guess you pick what you *think* is the best 
    fuel and oil for your boat, and hope for the best. 
    Rick

    .8 see .9
    
    Right Rick.  Makes sense to me that running a higher octane in a
    2 stroke 'can't hurt'.... at least compared to pinging.  I have
    run my Johnson 25 all summer on nothing but premium.  Have had NO
    problems.  So what does that tell me?  I am doing something right.
    Since this engine sips gas (its really easy on fuel) I can afford
    to feet it 'the best' so will continue to do so.
    
    Jeff

    re: octane,  apologies if this has been covered or is overly simplistic.
    
    Octane is in one sense a measure of how easily vaporized fuel will
    ignite.  The higher the octane, the *less* easily it will ignite.  This
    matters because in higher compression engines, one wants to avoid
    auto-ignition due to the heat of compression (the way a diesel runs),
    which by definition in a gas engine is pre-ignition--not good.  A less-
    easily ignited fuel can be compressed further and still "wait" for the
    spark plug to ignite it at the right instant.  Pre-ignition is often
    manifested in "pinging" or "knocking".  Additives, including 2-cycle
    oil I'd guess, can affect octane.  
    
    Apart from the choices of additives and what function they perform
    (e.g., detergents keeping carbs or fuel injectors clean), if the fuel
    is high enough octane not to self-ignite in your engine, higher octane
    beyond that minimum requred is just a waste of money.  There's no more
    energy in higher octane gas than in low octane gas, only differences in
    how it can be obtained.
    
    J.

    re: .11
    
    Agreed - more octane than necessry is a waste of money.  But what I 
    think Jeff is saying in .10 is that the few extra dollars he'll spend 
    in a season on premium is cheap insurance compared to the cost of an
    engine rebuild.
    
    In other words, if you're going to use the wrong grade of gas, too much
    octane is better than not enough.
    
    Rick

    Also, In my experience, many gas docks (from Lake Winnipesaukee to
    Bailey's Island, Me. and several in between) only have premium grade
    at the pump (singular).
    
    Bill
    

     The harder the fuel is to ignite, the more of an octane rating
    it get's........ This makes me wonder. Does adding oil to the
    fuel ( 2-stoke ) make the octane rating go up?? I would think
    that the oil has a very high octane since it isn't easily ignited.
    This could explain the high compression in 2-stokes and diesels.

    Any Ideas ????

    Mark.

    re: .14
    Your reasoning makes sense, but it actually works the opposite way.
    Oil mixed with the fuel actually lowers the octane rating since oil 
    has a *low* octane.  Have you ever noticed that older cars that
    burn oil also tend to have severe pinging problems?  I had an old
    Cougar that under certain conditions while accelertaing had lots
    of blow-by and blue smoke. Every time the smoke started, the motor
    would ping VERY badly.
    
    Here's another curve ball for ya.  Adding oil to the fuel leans the 
    fuel/air mixture, which further increase the likelihood of pinging. 
    There is a certain ratio where engines run the most efficiently, I 
    think around 13:1 or 14:1 (measured in POUNDS of air and fuel). Any 
    amount of oil added to the gasoline decreases the amount of gasoline 
    available for a given volume.  This is all figured in when the 
    engineers select the jets for your carubretor(s).  But if you mess 
    with the fuel/oil ratio either accidentally or intentionally, you're 
    also changing the air/fuel ratio, however slightly.
    
    Rick

    Mark - I'd say you were right. I would imagine oil is much harder to
    ignite that gasoline. Adding that oil to gas would raise the temp at
    which the gas ignited. (At least that would be the premise) The problem
    is that there are many different oils, and different gas companies
    use different methods (And additives) to raise the octane of the gas.
    So at least at this point I imagine its impossible to predict the
    outcome.
    
    BTW - octane does not exactly refer to how difficult a fuel is to
    ignite. It *only* refers to a fuel's resistance to detonation. There
    are many many factors that can affect this. The spark of a spark plug
    is many thousands of degrees which even with the highest octane of
    fuels will have no trouble igniting. And indeed the difference in
    temperature of ignition for low and high octane fuels is on the order
    of only several tens of degrees.
    
    				Kenny

    Rick summed it up when he said since I don't know whether my 2 stroke
    is pinging or not any mistakes 'should' be made toward a higher octane.
    I can't hear the engine ping... but have been told one can't hear a
    2 stroke ping anyway.
    
    Do any of you remember the movies which typically would have an 
    aircraft (circa 1950's) crash and burn with 'all that high octane
    gas'?  The implication being that since it was high octane av gas
    the fire would be more intense and more easily ignited.  Ironic
    to find that any planes loaded with regular gas would have burned
    just as intensely and easily.  When starting a gasoline crash fire
    I doubt if a few milliseconds in ignition time could be observed
    by bystanders.
    
    Jeff

     I see, the octane is the resistance of 'detonation due to compression'
    vs 'ignition from the spark'. Makes sense to me. That's why Diesel fuel
    is actually low octane so it can be detonated easily without a spark.
     I knew I'd get the right answer from someone out there. 8)

    Mark

    While I agree with the comments about not buying higher octane gas than
    the engine needs, I am also concerned with detecting pinging in a
    marine engine. In my car I can depress the accelerator slightly going
    up a hill, inside a quiet car interior, with the engine right in front
    of me and hear it ping. I have a gas stern drive as well as an older
    18HP outboard on an aluminum row boat. I do not know how you would ever
    hear either one ping with wind noise, spray noise, and engine noise.
    Unless it preignited so badly that performance was effected, how would
    you know? My Mercruiser manual calls for 87 octane and I buy the middle
    level gas (on the highway, not at a marina) and paid $1.24 for 89
    octane versus $1.18 for 87 octane and figured it was cheap insurance. I
    have also read that a boat engine sees a load like a car always going
    uphill, which is when a car engine usually pings. I also know that
    octane may vary somewhat with each tankful, since my car will usually
    run fine on 87 but will sometimes ping slightly on some fillups, and
    then be fine on the next. The 89 in the boat, I feel, also allows for
    some variation. Carbon deposits on the cylinder head, valves and
    pistons, will also over time raise the effective compression ratio
    slightly, so an older engine may need a higher octane fuel to prevent
    preignition.
    
    To sum it up, I would like to use the lowest octane fule on which the
    engine will not ping, but I am concerned about whether I could detect
    it if it happens.
    
    Larry 

    Good point.  The load a boat engine sees is considerably DIFFERENT from
    an auto or truck engine.  A boat engine often runs at a CONSTANT LOAD
    for extended period of times with little variation is RPM.  An auto
    engine (even on interstates) often see a variation in load with 
    traffic, uphills, overrun on downhills etc.  Boat engine valves have
    a tough life because they have little chance to cool off on overrun
    going down hills.
    
    

    If you want an explanation of octane, at a microscopic level, it
    is the length of the molecule that makes it slower burning.
    
    Regular gasoline is composed of hexane or heptane, which, if I remember
    my highschool chemistry from 30 years ago, have 6 and 7 carbon
    atoms respectively. The octane molecule has 8 carbons, and therefore
    burns more slowly. The higher the percentage of octane molecules in a
    given gasoline mixture, the slower it burns.
    
    Bill
    

      Yeah Bill, I remember that stuff too, but didn't remember enough of
    it to actually talk about the molecules. That is where the phrase 'high
    in octane' or 'high octane' came from. Octane (One of the substances
    you get when you crack oil) has a greater resistance to knocking. The
    problem is that it is more expensive than the other parts, so oil
    com[anies only blend in enough to get the job done.
    
      Now comes the fun part: these days, there are many other ways to
    raise the octane *rating* in addition to or other than TE Lead which is
    now outlawed. I think it is some of these new chemicals that are being
    used that are somewhat incompatable with 2 stroke oil. It may take a
    while for it to shake out. There's no telling if we'll end up with
    differently blended fuel so it doesn't happen or a change (or additive)
    in the oil to prevent it. Considering that it took several years for
    the fuels to change to stop the problems with fuel injectors and the
    difference in numbers of vehicles, I would say that if the oil doesn't
    get changed nothing will happen.
    
    				Kenny

RE: Note 1018.22 
>> Octane (One of the substances you get when you crack oil) has a greater 
>> resistance to knocking. 

I didn't realize that there is an actual "substance" called octane - I thought
it was simply a rating system which measures resistance to knock or ping.  Is
this where the new standard of "R+M/2" comes from?  Research method is the
theoretical or calculated octane rating, and the Motor method is an actual
test under cotrolled conditions, using I think a small block Chevy built to
an industry standard configuration.

>> Considering that it took several years for the fuels to change to stop 
>> the problems with fuel injectors and the difference in numbers of vehicles,
>> I would say that if the oil doesn't get changed nothing will happen.
    
If the current problems of carbon and stuck rings is in fact caused by the 
new additives for fuel injection, I think you're right that any improvements
will have to come from changes in 2 cycle oil.  In the overall scheme of things,
the amount of fuel destined for 2 cycle use doesn't amount to much more than a 
drop in the bucket, and probably isn't much of a concern to the oil companies.
OMC has recently come out with TCW-III oil - anyone know whether it's supposed 
to help with the carbon and stuck ring problem?

Rick

    I thought the Motor was a standardized single cylinder thingy, to
    minimize the number of variables, like intake runner lenth, bla bla
    bla...
    
    On 2 strokes with aluminum pistons, experts can read ping on the spark
    plugs (little bits of aluminum?).  They also use fiber optic scopes to
    look at the pistons thru the sparkplug hole.  If you got ping, what you
    hear is the top of the piston being blown away a bit at a time!
    
    Mechanics use a stethoscope thingy right on the engine block to hear
    what's going on inside (wrist pins, piston slap, lower end knocks, etc.) 
    but you could do the same with a piece of tubing.
    
    Carl
    

    As I understand it the reason diesel engines are slow on pick up (I
    have a diesel in my car) so I speak from experience as far as diesel
    acceleration is concerned, is because diesel fuel burns more slowly
    than gasoline. BUT perhaps although it BURNS slowly it IGNITES easily.
    That doesn't make sense to me though because a match ignites gas with
    no problem... but drop a lit match in diesel fuel and the match goes
    out.  Well perhaps thats ignites easily under COMPRESSION!?
    
    Jeff

RE: Note 1018.23 (by me)
>>OMC has recently come out with TCW-III oil - anyone know whether it's 
>>supposed to help with the carbon and stuck ring problem?

I have the answer to my own question.  The current issue of "Boat and Motor
Dealer" has a brief writeup on the availability of the new TCW-III oil from
OMC.  It said that the new oil is in fact intended to help solve the carbon
and stuck ring problem being caused by changes in unleaded gas.

The article also said that it could be expected that TCW-II oil would be 
phased out.  I find that doubtful, seeing as many companies are still 
selling oil that's not even TCW or TCW-II rated yet.  I recently noticed 
that my father's been using gas station brand oil in his boat, which isn't 
TWC rated.  It said it was "NMMA" approved and to the novice (like my Dad)
looked like a good grade of oil.  I showed him that it was at least 2 levels 
below the TCW-II rating that he should be using.  Needless to say, he's now 
using TCW-II.

Rick

    
      In diesel engines, almost all of the fuel ignites at the same time
    which is exactly why it sounds a lot like pinging in a gasoline engine.
    The reason being that in a gasoline engine the fuel is *supposed* to
    burn at a certain rate. The 'flame' spreads through the combustion
    chamber ideally evenly. As this happens, the pressure (And thus
    temperature) rises. If the fuel ignites on it's own because it went
    over some magic temperature, then things happen too fast and you get
    the pinging - because it is actually like a little explosion rather
    than a controlled burn. The pinging 'sound' is actually the shock wave
    caused by the 'explosion'. Deisel engines have lots of compression so
    that they can be SURE they exceed the temp of the deisel fuel's
    ignition temperature.
    
    				Kenny

    Diesels are also robustly designed to be able to handle the constant
    pinging nature of the fuel burn.  I have a diesel and at idle
    especially it sure sounds like ping to me.  I don't know as I have
    ever heard a diesel that didn't sound like it was pinging.  Remember
    when Olds dieselized a gas 350 block and created a nightmare of
    problems?  They also came close to ruining the reputation of diesels
    in automobiles.
    
    I have an 86 Isuzu Trooper with a diesel in it. (Yup they put 
    diesels in Troopers back in the mid 80's).  At about 40 K miles
    my engine threw a rod right through the block.  It turned out that
    they had added a turbo charged to a standard diesel block and the
    connecting rod (big end) bolts fatigued and broke.  So they had to
    beef up the big end rod bolts.  They replaced the engine 'free'
    (new block) with the beefed up version and 60 K miles later it is
    still running fine.
    
    It seems when corners are cut eventually things catch up with you.
    
    Jeff

    Moved by moderator...
    
================================================================================
Note 1021.0                 SOME MORE INFO ON OCTANE                     1 reply
NEST::GREENLAW                                      102 lines  30-SEP-1992 13:07
--------------------------------------------------------------------------------

    
		ARE YOU BURNING THE WRONG FUEL?

	All the rules have changed.It used to be taken for granted that if
you engine was built to burn 87 octane gasoline,you were foolishly pouring
money down the drain if you filled up with anything higher.But now it may prove
 costly to run on anything LESS than 91 octane-not because of the octane rating
 itself(a measure of an engine's resistance to detonation),but because 91 octane
gas burns cleaner,and contains an engine saving "dispersant" additive.

	The problem is that,faced with squeezing more gallons of unleaded out
of a barrel of crude oil,petroleum engineers changed the very chemistry of
gasoline and created a Frankenstein fuel in the process.It was a simple matter
of bottom-line economics.The bean counters got what they asked for-at the 
expense of your engine.

	In simple terms,87 octane gasoline has become a dirty liquid not fit
to fuel a lawnmower or weed trimmer (see box)***,let alone a marine engine.It 
poses more problems to some engines than others,and whatever damage it will
ultimately wreak depends on whether you're running an inboard,a stern drive,
or an outboard.

	On cars,inboards and stern drives the junk gasoline plugs up fuel
injectors and forms deposits on the undersides of the intake valves.Telltale
symptoms are poor idling and stumbling on acceleration.Potentially,there's 
also a loss of horsepower,which you may or may not notice.The buildup on the
intake valves restricts the fuel/air flow.Performance is hampered,but the
engine is not in imminent danger of breakdown.On the other hand,to correct
this performance problem you may well have to pull the head,which can translate
into a greater expense than the added cost of premium fuel.

	The fate of an outboard motor burning 87 octane gasoline,however,is
nothing less than disastrous.When an outboard burns 87 octane,carbon forms
on the sides of the piston.Engineers refer to this as "coking".As the carbon
builds up on the pistons,it acts as an insulator,preventing the combustion
heat from escaping through the cylinder walls and into the coolant flow.The
more coking builds up,the higher the piston's operating temperature climbs.
The excessive heat expands the aluminum until the pistons try to grow larger
than the cylinder bore.Somewhere along the line the motor self destructs.

	Note:Because four-cycle engines run about 200 degrees F. cooler than
outboard motors,they don't seem to be affected by piston coking.

	So how long does it take for coking to reach critical proportions?
According to OMC engineer Steve Towner,given two outboard motors,both built
to burn 87 octane gasoline and all other factors being equal,the motor
burning 91 octane gasoline will generally last THREE TIMES LONGER than its
counterpart.

	What about dosing cheap fuel with aftermarket additives in order to
bring it up to speed? Keep in mind there are two basic types of additives:
detergents and dispersants.Detergents are intended to take care of the 
carburetor and upper intake track of the engine.Unfortunately they cause
MORE coking and more deposits on valves and pistons than if the additive were
left out altogether.This is true with both outboards and four-cycle engines.

	The dispersant class of additives,however,cleans the upper intake and
also keeps valves and pistons squeaky clen.But 87 octane gasoline has recently
reached a state of such poor quality that dosing fuel with a dispersant is
still a waste of money.There isn't enough dispersant in the world to make a
difference-the coking problem will simply not go away.

	According to one oil company spokesman,you're definitely better off
buying 91 octane,which is made from a better stock of gasoline,and which
already has a dispersant included in its additive package.

	Even if your engine was built to burn 87 octane gasoline,you're money
ahead burning premium instead-not to defeat knock and ping,but for its inherent
quality and its additive package.




	*** BOX 

	Super for everything? Although many manufacturers of small two cycle
engine equipment recommend the use of 87 octane,I would still use 91 in my
lawn mower,chain saw,leaf blower,etc.,because the coking problem still pertains.
BUT I would check the alcohol content (to make sure it is less than 10 percent)
with a test kit,because excess alcohol impedes lubrication and attacks fuel
system components.Alcohol detection kits are available from such suppliers as
Kent-Moore Tool Group (part no.J34353),29784 Little Mack,Roseville,Mich.,
48066-2298. 313-774-9500. Unscrupulous gasoline blenders have been known to 
drown gasoline with as much as 50 percent alcohol to raise its octane.


						by Tim Banse

	(Gas engine expert Tim Banse is a factory trained mechanic who has 
	been a marina service manager and has written books on marine engine
	performance.)


	This all came from the Feb.91 issue of Motor Boating & Sailing
	magazine.Reprinted without permission.




Keith G.
	

    I agree 87 is the garbage of the industry.  Outboards run hotter
    because they are 2 stroke engines firing every revolution, 4 strokes
    have more time to shuck off the heat, therefore don't coke.  
    
    I have an 84 Dodge Colt Turbo with about 130 thousand miles on it.  
    It will run on 87 octane, because the knock sensor will back off the
    timing.  I've always run 91 or better in it, and have yet to change the
    oxygen sensor.  It always passes the emissions test in Mass at the
    lowest that the machines will record.  It's on its third set of spark
    plugs.  
    
    The oil gets changed every 10 or 15 k, or when I get around to it.  
    
    I have never touched the injection system.  
    
    I attribute this solely to running the better grade/quality gasoline.
    
    If you like fixing engines, run 87 octane.
    
    Carl
    
    PS:  Sorry for the none boating digression.

    
    Some things dedend on what you can get. Larger boats that cannot
    be trailered, must fuel dockside. Most all of the fuel docks
    sell 89 octane.
    
    Jim.

RE: Note 1018.30
>> Outboards run hotter because they are 2 stroke engines firing every 
>> revolution, 4 strokes have more time to shuck off the heat, therefore 
>> don't coke.  
   
Well, I guess in theory a 2 stroke would run hotter because it fires on
every stroke.  But you're forgetting that outboards have a constant,
unlimited supply of cooling water that's rarely over 75 degrees.  With
most outboards you can easily hold your hand on the engine block while
at operating temp, except near the exhaust ports.

The reason 2 cycle outboards tend to coke or carbon has nothing to do
with excess heat. It's because they're burning a fairly rich mixture of 
oil, while 4 cycles are burning gasoline only.  If anything, most outboards 
don't run *hot enough* to burn off the carbon.  From my own experience
anyway, your mileage may vary of course.

Rick

    
      Gasoline of ANY octane rating can contain as much or as little
    detergents, dispersants or good or bad octane boosting additives as the
    manufacturer wants to put in it. Higher octane fuel never burns
    'inherently' cleaner than lower. A fuel's octane rating is ONLY a
    measure of it's resistance to knock - NOTHING else. That there may be
    better fuel stock or more detergents etc., is merely a *possible* (But
    never guaranteed) side benefit.
    
      I also agree with Rick about two strokes not running hotter than 4
    strokes. All engines are different. Depending upon how they are tuned,
    one may or may not run 'hotter' than another.
    
    				Kenny

    Sounds as if running premium in outboards is a cheap investment in
    extending engine life given the information presented a few notes
    back.  Granted, a better additative package is not guarantted by running
    higher octane fuel.  It does sound as if 87 octane gasoline was
    designed to be as inexpensive as possible and it stands to reason that
    if expense if the issue that petroleum engineers would omit whatever
    they could to barely do the job of running and protecting your engine.
    
    I have heard it argued that running premium is not environmentally
    sound is your engine doesn't need premium because it takes more oil
    stock to manufacture premium.  HOWEVER, if emissions go up with a lower
    grade of fuel then I wonder if the environmentally sound statement
    still holds true.
    
    Jeff

    
    
    	Just a side note to this discussion:
    
    	A couple of weeks ago while driving home I listened to an interview
    	on an am radio station.  I can't remember names, but this person
    	was a representitive of a consumer group that had been doing a
    	study of marketing methods used by the oil companies.  The results 
    	they sited were that oil companies, through marketing, attempt
    	to make you "believe" that the higher grades of gas have more
    	additives/detergents than the lower grades, when in fact, ALL
    	grades had pretty much the same additives.  They (the consumer
    	group) were introducing legislation (JUST what we need...) to
    	force oil companies to refrain from this type of marketing, as
    	it was ripping off consumers to the tune of millions/yr.
    
    	I don't know how much of this to believe...I find it terrilby
    	confusing, and it seems that those things that are "true" are
    	not necessarily true ALL the time.  So.  In order to sleep at
    	night without worrying about wether the tank(s) I burned that
    	day had done damage to my outboard, or if I had wasted money
    	by buying supersuperplussuperregular gas at $1.80/gal, I use
    	the middle grade, and continue to use the anticarbon additive
    	the johnson dealer recommended.
    
    	Jim

    As Kenny said, the octane rating only pertains to resistance to
    knock and does not guarantee a higher level of detergency.
    
    For whatever it's worth, Texaco advertises that it has the same
    high detergency in all 3 grades of their "System 3" gas.  Therefore,
    the only difference between the 3 grades *should* be their resistance
    to knock or ping.  I run my '92 Nissan pickup mostly on Texaco 89 
    octane, and it runs fine with NEVER a trace of knocking, while 
    getting 29 mpg. 
    
    Rick

    
    On the subject of cold and hot. All inboard 4 cycle engines
    do not run at the same temp. A raw water block will typically
    run between 140 and 150 F.  A Fresh water block will typically
    run at 160- 180 F, more so closer to 180. 
    
    Some one mentioned a 200 F block earlier, i would think it
    was an auto/truck read: land vehicle.
    If not something needs to be done and soon.
    
    
    I have a 91 chevy truck, and i have been told in no uncertain
    terms by the dealer to run 87 octane, lower if i could find it.
    The gas hype about user higher octane when not needed is a crock
    of *&^%. 
    
    For info sake, does anyone have a copy of the BMW chart for
    Octane ratings???
    
    JIm....
    

    I run a 350 cu in Chevy V8 in my truck. The engine is very sensitive
    to gas grade.  87 octane......PING!  89 octane very little ping on
    hard acceleration, 91 octane no ping I can hear.  So as far as
    octane is concerned I can hear a difference between grades.
    
    With my 25 Hp Johnson 2 stroke outboard I figure the slight added
    expense of premium is well worth it in peace of mind and engine life.
    
    Jeff

RE: .37
>>    On the subject of cold and hot. All inboard 4 cycle engines
>>    do not run at the same temp. A raw water block will typically
>>    run between 140 and 150 F.  A Fresh water block will typically
>>    run at 160- 180 F, more so closer to 180. 
  
You're confused Jim.  Nobody said raw water and fresh water cooled motors
run at the same temp.  The statement was that 2 cycle motors run hotter
than 4 cycle motors, which is not necessarily true.  The type of cooling
system (fresh water, raw water, air cooled, etc.) is much more a determining 
factor.


>> I have a 91 chevy truck, and i have been told in no uncertain
>> terms by the dealer to run 87 octane, lower if i could find it.
   
Hmmmm, I'll be careful not to buy your truck when you trade it in.  8^)
Sorry, but I don't buy the dealer's spiel that you should use the lowest 
octane you can find.  If your motor is computer controlled, you could 
probably run it on 70 octane if you could find it.  But the computer
would have the timing so far retarded the thing would be a pig, with
no power and lousy mileage.  Sometimes you can SAVE money by running
higher octane and advancing the timing a bit to compensate.

Rick

    
    I was only pointing out the difference in 4 cylces.
    
    As for the truck its very much in warranty.
    
    Its a 350, i've run the higher octanes, both 89 and 92.
    
    It made no difference in performance, or milage that i could
    tell.  Seems that 87 does the job.  I'd like some facts
    and not opinions.   
    
    If you look at the BMW table you'll find some facts.
    
    They specifically recommend brands of gasoline to ues,
    and not to use.
    
    JIm.

    Do I have to buy a BMW to get the table...  ;-)

    no..