Easy there, Fred. The "real" answer is as it frequently is in these
groups - RTFM!
(That's "Read the F-ing manual, for those that don't know.)
The manual doesn't usually say "premium" for the reason that Dori
mentions - different methods in different countries.
On 24 Jun 2006 16:43:14 -0700, " email@example.com"
My perspective is that this is a false economy. I don't know about
the 1994 model, but my 2003 325i and Z4 have 14.5 gallon gas tanks,
one of which I fill once a month. Going down one grade of gas will
save me $2.90 per tankful at the most. Less than an espresso drink at
Starbucks, an issue of Bimmer magazine, a movie rental at Blockbuster,
or a pack of cigarettes. Getting a BMW and then cutting corners is
like ordering custom-made dress shirts made with a cheap poly-cotton
2003 BMW 325i Black/Black
2003 BMW Z4 Black/Black
Agreed, the savings are small. But isn't it true that most recent BMWs
can automatically adjust certain aspects of engine operation to match
lower octane gas? In other words you may sacrifice a little performance
but no harm will be done.
Yes, that is true of almost all cars today. If the engine has a knock
sensor, it can sense detonation and retard timing and make other small
changes until the engine can live on the fuel you feed it.
In most cases you will lose power and also fuel economy. If you lose
more than 8% in fuel economy, it's a wash and you'd be just as well off
buying premium for $.20 more per gallon.
In my case, my Z3 1.9L gets 26 mpg on premium 93 octane. If I drop
to 91 octane and get 25 mpg, or 87 octane and get 24 mpg, it will be the
same fuel cost per mile. Smiles per mile will also drop.
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