High Gas Prices Fuel an Octane Rebellion 2000Rod Speed Absolutely relevant - See premise #2 in the buttignment I give you below. Again, see your buttigment below. Really? Hope you are ready to explain your position below. Here's your buttignment. It will...
SMS
There is ALWAYS wasted energy. In the form of heat, unburned fuel, etc. Engines are not capable of converting every available "BTU" into power to move the car.
I will not try to cop out like the Speedfreak and say that your point is irrelevant. You are correct that the big difference is when running the engine flat out. That was something that Scott couldn't seem to get a handle on - My ORIGINAL point in my response to him was that even if the engine maker recommends high octane, moving down a grade or two will not destroy the engine under typical, everyday use. Most people would never notice.
But the automatic adjustments made to compensate for the lower octane in a higher preformance engine will impact mileage, (as well as the higher end of performance). I said it was probably less than 1 mpg for most.
Actually, it probably wouldn't. Just like a "high perfromance engine" would have to "adjust down" a bit to compensate for the lower octane. The typical engine is capable of "adjusting up" a bit too.
You won't necessarily increase performance of the standard engine from HP standpoint, but being able to advance the timing and-or lean the mixture a bit by themselves without knock WOULD increase mileage. But since the recipe for making the higher octane fuel reduces the the fuel's energy content, the whole thing ends up to be pretty much a wash in the standard enigine. This is why it's a waste of money to by higher octane than required.
Ethanol is not that cheap. MTBE was the preferred ingredient for raising octane rating because you use a lot less of it for the same effect.
