fuel economy

[kohlers]

Today I filled my tank from 1/4 with 87 octane. I did not notice any difference in performance from 91. I am new to BMW, only about 500 miles in my 2000 323i. Now I would like to know if someone has any numbers for MPG with 87 versus 91 octane.

[kohlers]

OK, guys after I submitted the above I found a whole lot of discussions of 91 vs 87 etc. Much of it seemed very uninformed. Well, on my fuel-door it recommends 91 but do not go below 87. The engine adjusts the timing automatically to the octane. Certainly 91 gives better performance for those who need it. I do not. The question is MPG. The difference in price between 91 and 87
may or may not make 87 more economical. 87 will NOT hurt the engine at least not mine.

[nukeduster]

It can, just like oil brands, this has been beat to death 1 million times before on 1 million car forums. No one will ever agree, because everyones opinion is stated as fact, because someones friend of a friend is a scientist for some super lab somewhere who knows whats best. Whatever works for you, whatever brand makes you get the best mpg, is what works best for you. I personally use shell V power 91 octane fuel. I get the best economy and power with it compared to other brands and octane ratings. YMMV.

[kohlers]

Thanks, I believe you. I think what you are saying is that octane rating is not all. The additives used by various companies makes a difference too, especially in a high compression engine like the BMW.
Sorry, I have only been on this (or any other) forum for a couple of weeks and did not know of past discussions.
I think I saw someone found 87 to decrease MPG by 2 which is roughly 10%. Price difference between 87 and 91 is about the same, 10% so it seems just as well to use 91 ( and a good brand gasoline). Thanks.

[johnnyBgood]

Originally Posted by nukeduster

It can, just like oil brands, this has been beat to death 1 million times before on 1 million car forums. No one will ever agree, because everyones opinion is stated as fact, because someones friend of a friend is a scientist for some super lab somewhere who knows whats best. Whatever works for you, whatever brand makes you get the best mpg, is what works best for you. I personally use shell V power 91 octane fuel. I get the best economy and power with it compared to other brands and octane ratings. YMMV.

+1^

[RDroz]

Tucson is over 2000' above sea level. Your car won't make as much horsepower there as at sea level as the air is thinner. You likely can run fully advanced timing on any grade of gasoline, so you won't see a drop in mpg or a change in performance.

[kohlers]

Thank you RDroz. Reduced performance at altitude I know from flying my plane (non-turbo). But I do a lot of sea-level driving so I would still like to know if someone has any fuel-burn numbers for 87 vs 91 grade.