gasoline for lawnmower

[salty]

It most definitely hurts, and can lead to an expensive rebuild.

[salty]

FALSE, if by "fuels" you mean gasoline. Higher octane is expressley there to make the fuel burn slower. That is the purpose of high octane in gasoline. What did you think it was for?

[trader4]

I agree. A year ago I forgot to run the snowblower dry and since I normally do, it didn't have any stabilizer either. Come winter, it wiould not start. I wound up having to pull the carb, buy a rebuild kit and clean it. No question there were gum deposits inside which were the problem. After that, it started right up. So, with about

13 years of experience with no problems, having it gum up the one year gas was left in it is evidence to me that it's not a crock.

I drain the snowblower and add sta-bil to the lawn mower.

[Tony]

Rich as in someone paid too much for it.

[HeyBub]

Not even an air boat? How about a sea plane?

[clare]

Well you are talking to the wrong person if you are expecting someone to believe rate of burn, or rate of combustion has anything directly to do with octane. A FASTER burnig fuelis actually LESS likely to detonate, because the "end gasses" of combustion are exposed to high heat and pressure for a shorter time, and therefore are less likely to dissassociate and turn into unstable radicals, which then "detonate" in the cyl.

High octane is NOT to make the "fuel" burn slower. It is to prevent the "fuel" from breaking down into unstable compounds which "explode" in the cyl.

That I KNOW for a FACT. TEL and other octane enhancement chemical additives in fuel act as "anti-catalysts" to prevent that breakdown or disassociation.

[clare]

Well, I have several (4) decades of experience as a mechanic that re-enforces what I have been taught - high octane fuel will NOT damage an engine. High LEAD fuel can damage an engine. High lead fuel is high octane, but high octane does NOT need to be high lead.

Propane is 115 minimum AKI and unless it is run too lean it will NOT harm an engine (if the engine has hardened valve seats designed for lead-free fuel) High octane unleaded motor fuel without ethanol likewise will not harm any engine designed to run on regular unleaded gasoline.

[AZ Nomad]

bullshit.

agreed. octane is basically the fuel's resistance to preignition. Going higher than necessary is a waste of money, nothing more.

[mm]

I read what you have below, but I know I was told something like my paragraph just above. Maybe even heard it on the radio. I googled a bit now and can't find anything to support my statement, however. Do you or anyone know what I could be thinking of? Was it a hoax? Does anyone remember it?

[salty]

Now that there is COMEDY GOLD!

[salty]

Wrong. Dead, completely wrong. Running High Octane gasoline in a low compression engine that is not designed for it will cause excessive carbon buildup which can lead to frozen and broken rings, cylinder scoring. The carbon buildup can also lead to pre-ignition which can trash the engine, too.

Your 4 decades didn't teach you much.

[salty]

Okay, you are wrong, too, then.

[AZ Nomad]

Name one case of an engine destroyed by too high octane fuel.

Otherwise, you are shown to be talking out of your ass yet again.

[clare]

A sea plane yes - an air boat no. At least in Ontario.

[clare]

You need to understand the difference between detonation and pre-ignition. Pre-ignition is ignition instigated BEFORE the spark fires - generally from a hot spot in the cyl. This can be a sharp valve edge, glowing carbon, overheated spark plug, etc.

THAT is not detonation, and higher octane fuel will NOT prevent, or even reduce it.

Detonation is the "explosion" of the destabilised end gasses, usually farthest from the spark plug, in static pockets, due to high heat and pressure causing the hydrocarbons to dis-associate.

Octane rating indicates the ability to resist this spontaneous, uncontrolled burning after ignition has occurred., and a faster burning fuel is less likely to detonate than a slow burning fuel (natural octane, I like to call it) This is also why detonation GENERALLY occurs at lower speeds and under high load, not at higher engine speeds.

Detonation can CAUSE pre-ignition, but is not detonation. Detonation can also CAUSE pre-ignition. If cyl head temperature increases and exhaust gas temperature drops, that is the surest sigh that detonation has occured,

How, or why, you may well ask?

When detonation accurs, it disturbs the layer of air directly against the surface of the combustion chamber, and "scrubs" it off. This layer acts as an insulator, preventing the total heat of combustion from being transfereed to the cyl head and piston. Whenit is disturbed, much of the heat of the exhaust is absorbed bu the piston and cyl head, reducing the exhaust gas temperature and raising the cyl head temperature.

Now, when this happens, parts of the cyl head and/or piston, and/or the spark plug, will overheat, and there becomes a high probability that the fresh charge of air/fuel mix will ignite spontaneously before the plug fires - classic pre-ignition.

If pre-ignition happens as a precursor to detonation, it is because the spark, occuring too early in the cycle, causes cyl pressures to increase MUCH higher than normal (expansion against a rising piston instead of against a descending piston) and that pressure and heat acts on the end gasses for a longer time, making the disassosiation and detonation more likely. Pre-ignition causes a normal, controlled conflargation in the cyl - just at the wrong time. Gives you the same effect as "spark knock" caused by over-advanced timing - which again is NOT detonation - but can cause detonation.

Pre-ignition and "spark knock" can be hard on bearings and pistons - causing causing cracked or broken pistons and/or pounded out bearings and/or bent rods etc.

Detonation, on the other hand, causes burned pistons and/or metal transfer to the spark plug, and/or cratered surfaces in the combustion chamber (looks like small sharp bits have been pecking away at the roof of the combustion chamber, or the top of the piston ) and aluminum "spray" on the plug tip, and CAN cause fractured pistons, damaged bearings, bent rods, etc along with the other signs of detonation.

Detonation causes overheating as well as being excaberated by overheating.

Pre-ignition is most often caused BY overheating.

Detonation as a precursor to pre-ignition is more common than the other way, but both are possible.

[clare]

Running too rich or too cold causes carbon build up. Running fuel with too much lead causes lead buildup. Running high OCTANE fuel causes NEITHER.

There is more MYTH surrounding fuel octane and the results of using octane higher than recommended for an engine than just about any other automotive or engine topic today.

Much of it is based on half-truths. A continental 85 aircraft engine, for instance, was designed to run on

80/87 octane aviation fuel (White) which had virtually no lead. It is no longer universally available, so users are forced to use either 100LL (Blue) or 100/130 (green) gas. The Lycoming O200 is another example. Using the highly leaded 100/130 will cause engine damage due to rapid lead buildup - particularly on the valve stems. Using "blue" avgas, 100LL, is less problematic as it contains significantly less lead (although still much higher than the old leaded super premium automotive gas) and can be used on these older engines with some caveats. Agressive leaning can be used to purge the lead, or certain additives can be used to keep the lead from sticking and remove lead that has accumulated (to a certain degree) Alcor TCP is one commonly used additive for this purpose. TBO on these engines when run on the highly leaded fuels is generally lower than it would be running 80/87, and Mogas STCs are available for many engines/planes to allow the use of 87-92 (minimum) octane unleaded automotive fuel - with NO ETHANOL. This is becoming more commonly available at many airports.

This is the basis for the MYTH that high octane fuel causes build-up problems and engine damage.

[salty]

Well, for openers I didn't say any engines were destroyed. So now who is making things up and talking out of their ass?

octane = burn retardant it slows the bang down for a more even, cooler burn thats how higher octane 'cures' pinging - by burning cooler and calmer

"Cooler" also promotes carbon buildup in engines that are designed to run on lower octane gasoline.

[salty]

octane = burn retardant it slows the bang down for a more even cooler burn thats how higher octane 'cures' pinging - by burning cooler and calmer

High Octane in a low compression engine results in cooler operation which promotes carbon buildup. You just said so yourself.

[HeyBub]

Giggle.

[AZ Nomad]

You said: "It most definitely hurts, and can lead to an expensive rebuild."