Best Gas Brand? Does it matter?

Originally Posted by Amil

when getting a ride from auto gallery back to my hosue dropped off the cayanne the driver was telling me that when they fill up for their cars (ferrari's, masarti's , porsches, audi) they always use SHELL so its gotta be good is what he said...

That's good to know...

Hey, I live in southern California (Los ANgeles Area) and I cannot find a gas station with over a 91 octaine raiting....Does anyone know perhaps why? Does anyone else know a specific place to get over 91 octaine? Also, somone mentioned they get Mobil 93, but Mobil isn't considered top tier....

Originally Posted by GoBlueBMW

Hey, I live in southern California (Los ANgeles Area) and I cannot find a gas station with over a 91 octaine raiting....Does anyone know perhaps why? Does anyone else know a specific place to get over 91 octaine? Also, somone mentioned they get Mobil 93, but Mobil isn't considered top tier....

That's because 99.9% of daily driven cars do not need anything higher than 91. You can do just as much harm by putting in too high an octane as you can too low an octane. The E90 should take 91, nothing more and nothing less. You can get away with 88-89 occasionaly though, but it's best to stick to 91.

Not true.

The octane rating is a representation of the anti-knock properties of motor fuel and nothing more. The higher the number value the stronger the resistance to detonation. Using fuel with a higher than recommended octane rating will not do you harm but you might be wasting your money.

I say "might" because even though 2 engines built by a manufactuer may be identical, but still they are not exactly the same and the octane needs of a given engine model can vary by as much as 6 octane numbers, so you could actually benefit from using higher than 91 or "get away" with using lower than 91.

Originally Posted by KUweatherman

You can do just as much harm by putting in too high an octane as you can too low an octane. The E90 should take 91, nothing more and nothing less. You can get away with 88-89 occasionaly though, but it's best to stick to 91.

Originally Posted by Toronto330

Not true.

The octane rating is a representation of the anti-knock properties of motor fuel and nothing more. The higher the number value the stronger the resistance to detonation. Using fuel with a higher than recommended octane rating will not do you harm but you might be wasting your money.

I say "might" because even though 2 engines built by a manufactuer may be identical, but still they are not exactly the same and the octane needs of a given engine model can vary by as much as 6 octane numbers, so you could actually benefit from using higher than 91 or "get away" with using lower than 91.

While I totally agree with you that using a higher octane is certainly a waste of money, I dont agree that there wont be any damage involved. In most cases, there probably wont be any damage. But there is the chance of carbon deposits building up in the emissions systems causing damage. By going with what you said, I could use 100 octane in my car and get away with it. We both should know this is certainly not the case. There is a reason manufactuers have a suggested octane. Stick to it...unless there is pinging, then go to the next highest octane. However, using 91 in the E90, this shouldnt be the case. If it is, there is probably a more important underlying problem.

The higher the octane the fewer double bonds that exhist between carbon molecules in gasoline. Gasoline contains many chemicals that contribute to the way it burns. With respect to damage done to the engine(not environment) the higher the octane the better it is for the engine (assuming any modern performance car). The more double bonds between carbon molecules the more "knocking" you get, that "knocking" can damage an engine over long periods of use. The reason for the "knocking" is due to the physio-chemical properties of gasoline and octane reduces those properties. In short if you have a BMW get the highest octane available. If you want more information about what "knocking" is and how exactly it works with respect to octane you can go to http://forum.e46fanatics.com/showthread.php?t=161055 and skip to the second to last post or just post here again and i'll try to explain in a different way.

I traveled from LA to CA on I-10 and I ran into the same situation with octane levels changing the further I went West. Of the gas attendants I asked about it they sad that elevation and climate was the reason.

Because there are only limited refineries and gasoline in the USA is often delivered by "independent" haulers that deliver for multiple branded stations, you have no idea if you're getting the brand that's posted. It's possible you're getting a name brand at independent stations, such as minit markets. The detergent additives are added when the tankers fill up at the refinery and you have no idea what additive package you might be getting.

I just fill up with Exxon Super.

I think this has more to do with the oil than the gas