RE: Octane vs. MPG

[Karl Zemlin <karl@xxxxxxxxxx>]

It's a myth  There's tons of stuff out there.  Here are a couple of
samples I turned up.

>From http://www.carjunky.com/news/newtext/40.shtml
- - Higher octane gas (super unleaded) does not give your car more power
or better fuel mileage. It means your car is more resistant to
detonation. Purchasing the more expensive, higher octane, premium fuel
provides no benefit to most cars. The only reason to use high octane gas
is if your car is starting to "ping" (which is also called engine
knock). This knock will not only rob your car of power and fuel mileage,
but more importantly, depending on the severity, can ruin your engine
over time. 

>From http://environment.about.com/library/weekly/blcars3.htm
Are you tempted to buy a high octane gasoline for your car because you
want to improve its performance? If so, take note: the recommended
gasoline for most cars is regular octane. In fact, in most cases, using
a higher octane gasoline than your owner's manual recommends offers
absolutely no benefit. It won't make your car perform better, go faster,
get better mileage or run cleaner. Your best bet: listen to your owner's
manual.

The only time you might need to switch to a higher octane level is if
your car engine knocks when you use the recommended fuel. This happens
to a small percentage of cars.

- -----Original Message-----
From: owner-bmw@domain.elided [mailto:owner-bmw@domain.elided] On Behalf Of
Stan Yoder
Sent: Tuesday, September 17, 2002 8:00 PM
To: bmw-digest@domain.elided
Subject: Octane vs. MPG


Is there general consensus that there is a c. 1mpg penalty if you go
from, say, 89 octane to 87 octane? That's what I've heard a coupla
times. If so, is this basically true for both city and highway driving?

Again, if so, simple arithmetic suggests there is no $ saving using 87,
assuming a 10cent/gallon diff in price between 87 and 89. IOW, the
dime/gallon saved using 87 is neatly canceled by the 1mpg loss.

Stan Yoder
Pittsburgh
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