E300POS - 4/28/2004 8:05 PM
I was referring specifically to comments like "if you want to be cheap, buy a daewoo" and others in that vein. The specific information regarding octane and how it is achieved is helpful and always appreciated. I simply have no patience for some who feel they've gained stature simply by writing a check.
I don't think you were aiming at me with that one. I should clarify one thing about my post, when I said I'd be buying the highest AKI I could, I assumed that would be 91 (the max here in SD) at one of my favorite gas stations and the minimum specified in my manual.
Higher octane is not necessary if it wasn't designed for it. I don't know what your owners manual says. Mine gives a cetane rating.
Cetane? Is your car a diesel? The cetane number is measure of the delay between injection and combustion I think. Using a higher cetane number doesn't buy you anything and has nothing to do with the quality of the fuel. As for octane, what you say is true, if the car can't adjust the fuel/air mixture, the higher octane rating doesn't buy you anything. Even if it does, it doesn't mean there is a performance increase.
In my poorer past, I had a large car with a400 CI motor. It ran fine on the regular grade of fuel. I also had access to aviation fuel. 115/130 if I recall. I frequently ran tanks of this fuel through my car. Other then a noticeable difference in exhaust odor, there was NO difference. The car did not knock but neither did it knock on regular. I suspect I would have lead fouled plugs if I ran it for too long on that fuel but I never had a problem with it.
If you used aviation fuel, your car (a newer car, that is) wouldn't be running too well for long because the lead in the fuel would ruin the catalytic converter. So, anyone thinking about doing that with a new car would be hurting their car not making it run better.
Premium and aviation fuels are not more explosive. They have the same BTU's per gallon.
A lot of folks think that higher octane means better fuel and that isn't the case. The higher octane, or AKI, doesn't indicate a higher energy density of the fuel. Or, like you say, it doesn't indicate that the fuel is more explosive. The octane rating only indicates how much the fuel can be compressed before detonating from the compression. The more the fuel can be compressed, the more fuel and air can be put in the cylinder. This is where the increased performance comes from. This performance increase can only come with an engine that has a higher compression ratio or a way to force more air into the cylinder.
Premium fuel is often a requirement of car engines as the design ages. As the engineers try to tweak them for a slight increase in power over the years and add turbos or superchargers or probably even increase the displacement on a dated design, premium fuel is an easy solution to stretch the engineering budget. That was a frequent occurence in the late 70's and 80's if anyone remembers some of those "cars".
I'm not sure I follow. Are we talking about an engine that aged or trying to put new life in an old design? If it is an older engine, using the higher octane fuel will not increase performance but it can reduce ping or knock which can be harmful to the engine.
In the case of extending the life of an engine design, unless the engine compression is increased, there is no need to use the higher octane fuel.
This is hilarious, if you put avgas in a car engine it will last less than it will with 87 octane. Being interested in aviation myself I know that 100LL(100 octane, LEADED) has been around since WWII, and the octane is so high simply because of the lead. same with the 60's race cars that ran on 100. I read that in the 50's they made 145LL, although I'm not sure how the octane gets to 145%. If you want the best, put Shelll Vpower in there, or if you are here in the states you put in 76 Ultra Performance, or whatever they call their 100 octane blend.
Yeah, this is pretty funny...
The octane rating, or AKI, is really an indication of how a particular fuel mixture resists detonation compared to 100% octane. Anything less than 100% would be made up of that much octane plus enough heptane to add up to 100%. Or, additives can be used to up the octane rating from a lower number. To get a fuel with an octane ratings over 100 you need additives, like lead, to get there or made with a "heavier" hydrocarbon. Isn't jet fuel basically kerosene?
Thomasbrown, where were you last Sunday, we missed you.