gas gas gas!

[Andres823]

I have a 2004 330i, with only 12K, when I took it to the dealer just to get it washed, one guy on sales told me that I could use gas with 89oct, instead of the 93 suggested on the manual, he told me that is for european cars, that here in the US the difference b/w 89 and 93 is nothing, that in fact, they use 89 to fill up all loans.
Then I talked to someone in service, he said the same thing, that maybe I should alternate b/w 93 and 89, and that the car should behave just the same, what do you guys think?
What do you use?

[///M Power]

Honestly, for the extra 10 cents a gallon I would just use 93. If it's recommended, it's done so for a reason. It's just one of those things in which you have to be confident in your decision about using th eproper gas and sticking to it. Of course a dealership is going to skimp here and there when they can. They use 89 because it is cheaper.

The fuel with higher octane usually contain more energy per unit measure. I could go into the significance of how different octanes and their similarity to % heptane act independentaly are, but I don't remember high school chemistry.

Also, different regions use different scales for meansuring Octane. Us being Americans, we have our own way (because we're smartasses like that). Europe I believe uses the RON method for measuign octane, versus the United States which uses the average of the RON and MON method, often seen as (R+M)/2 at gas stations. Now what the dealership told you may have been true of consider 93 octane Europe as 89 Octane here, if only they realized that our manual were made for America, and i'm sure our manuals recognize that in America the octanes are listed as the (R+M)/2 method. Did I confuse that? What im saying is 93 octane Europe as RON could be 89 octane (R+M)/2 here. Simply put, check your manual, if it says somethign about the rating system liek ROn and MON or (R+M)/2 then it is meant for US spec octane. If it doesnt mention any of that, assuem it's made for US Spec cars.

[drz]

Use 91 and higher. The engine management system can accomodate for lower grades (84 RON, which is equivalent to 87 US-spec, if I remember correctly), but that is less than optimal. You will have better fuel efficiency with the higher grade fuel. Savings at the pump are offset by expenditure in the cylinders. All this to say, the savings end up being negligible considering performance, engine cleanliness, etc. Stick with the good stuff.

[RexKing86]

^^ +1

[Hootie]

This has been beaten to death here. The 91 rating recommendation is Euro spec 91, which is the equivalent of US 87 octane. I routinely use 89 and have no problems. The fellas at Bavarian Auto have recommended to me that I could use 87 if I wanted to and it would have no detrimental impact on the car. About a year ago, I drove one month each on 87, 89, and 91 octanes. The 87 was a noticeable (I don't know how much) drop in power. No difference between 89 and 91.

[zibby]

Originally Posted by Hootie

This has been beaten to death here. The 91 rating recommendation is Euro spec 91, which is the equivalent of US 87 octane. I routinely use 89 and have no problems. The fellas at Bavarian Auto have recommended to me that I could use 87 if I wanted to and it would have no detrimental impact on the car. About a year ago, I drove one month each on 87, 89, and 91 octanes. The 87 was a noticeable (I don't know how much) drop in power. No difference between 89 and 91.

Agreed ! Adding 4 points to US spec(AKI), you get Euro spec (RON).which means 87 is 91 in Europe, 89 is 93 and 93 is 97.Remember 4 points rule for converting AKI to RON.