Octane

Subject: Octane
From: smorey@domain.elided (smorey)
Date: Thu, 19 Sep 1996 09:47:50 -0500
Prakash Maggan writes:

>I concur with Phil's suggestion. Before I added my Dinan chips
>I tried 87, 89, and 93 octane fuels and noticed an inverse relationship 
>with MPG and Octane. With higher octane I got lower MPGs.

I concur. As I understand it a higher octane fuel is simply less
"explosive" or less readily explosive to mitigate pre-detonation. That
being the case, --if-- there is any relationship between gas mileage and
octane it would seem that, as Prakash says, one would get a higher mileage
with lower octane. I've never noticed any difference and I check my mileage
by the gallons used / miles on odometer method (which BTW, has been 0.8-1.0
mpg better in reality than the computer records in 3 different BMWs we've
owned). Having said that, -even- if one were to get slightly better mileage
with premium (as someone said earlier in this thread) the savings would be
blown by the added cost for premium.

As far as better performance with premium, there is no way a less volatile
fuel will increase performance (unless of course your vehicle is -designed-
for premium in which case a lower octane might hinder performance through
pre-detonation). Ask the guy who burns nitro in his AA Fuel Dragster if he
thinks a less volatile fuel would lower his ET.

Steven C. Morey
smorey@domain.elided
Dallas, TX

BMW CCA #134873

1995 M3 (for sale)
1989 525i
1994 318is
1989 535i (remembered)
1981 633csi (remembered)