Which octane is best for our cars: 87, 89, or 93?

Dear Car Talk

Dear Car Talk | Jul 01, 1997

Dear Tom and Ray:

My wife, Gert, and I read your column every week
and enjoy it. Please clear something up for us
about gasoline octane. There is 87, 89 and 93 at
our local gas station. Which one is best for our
cars? We have a '93 Chevy Lumina and an '86
Mercury Grand Marquis. I am under the impression
that the higher-octane stuff is better because it
helps clean the engine. My wife says no. What do
you say? -- Bobby

TOM: Bobby, you should always listen to your wife
when it comes to cars! Haven't you learned that
from reading our column every week?

RAY: Gert is right in this case. Ten or 15 years
ago, when fuel injection was still relatively
rare, oil companies advertised that they added
special detergents to the higher-octane
gasolines. The reason, they said, was that these
detergents helped clean fuel injectors.

TOM: But now all cars are fuel-injected, and oil
companies say they add these detergents to all
grades of gasoline. So, as far as we can tell,
there's no longer any reason to buy any more
octane than you need.

RAY: How much do you need? In your case, 87 is
fine, Bobby. You've got two run-of-the-mill cars,
which call for run-of-the-mill gasoline. The
higher-octane fuels are designed for "high
compression" engines, which need a higher
ignition temperature to keep from pinging.

TOM: If you're in doubt about how much octane you
need, check your car's owner's manual. It'll tell
you what octane you need to keep the car from
pinging. Any more just creates more pollution and
wastes your money.

* * *

TOM: Well, you asked for it, and here it is. My
brother and I sat down and wrote down everything
we know about how to make your car last forever.

RAY: And it only came out to eight lousy pages!

TOM:But now this gold mine of information can be

RAY: Get your copy of "Ten Ways You May Be
Ruining Your Car Without Even Knowing It!" by
sending $3 and a stamped (55 cents),
self-addressed, No.10 envelope to Ruin No.1, PO
Box 6420, Riverton, NJ 08077-6420.

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