Re: someone please explain the "99 octane" stuff? (archive)

Octane is a measurement of the gasoline's ability to withstand detonation. The higher the number, the more resistance. Tetrahedral lead is a cheap and easy method of increasing octane, but since lead is not good for us and the environment, it was banned from motor fuels. Various other exotic chemicals are now used, but they are a lot more expensive and don't work as well.

Two methods are used to measure octane, Research Octane and Motor Octane. The number you see on the pump is an average of the two. Most pumps have RM+MO/2 or something similar on the yellow octane sticker just under the octane level.

Premium fuel nowadays is nowhere near 99 octane. Not only are you not getting the octane, you're not getting the lead which was used in older engines to cushion the valve seats. On the other hand, the spark plugs and valve stems don't get fouled with lead any more.

Some people go to the local airport occasionally and get 100 octane aviation gasoline (Don't use 80/87). Even the "low lead" 100 octane has a lot of lead in it and supposedly is good for the '70s engines. Of course you wouldn't want to put it in a car with a cat, but that shouldn't be a coupe owner's worry.

Don't expect to be able to just drive out to the pump at an airport in the Bay Area. If you know someone who has or rents an airplane, you might be able to get a gas can filled. Remember that the can will be contaminated with lead. It might not be worth the trouble, but some guys swear by it.

Follow Ups:

Re: 100LL gas Dave B 18:11 9/23/2001 (2)
- Go to Corona, it's "only" $2.14... coupeless 18:38 9/23/2001 (1)
  - Not on E34 Dave B 19:50 9/23/2001 (0)
thanks, that makes sence now andrey 12:05 9/23/2001 (1)
- Re: thanks, that makes sence now coupeless 12:23 9/23/2001 (0)

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