[bimmer456]

89=less power

[Billfitz]

89= less power if your engine has a high enough compression ratio and boost pressure to make use of higher octane. Otherwise all you're getting for the extra money spent is a good dose of placebo effect. My bet is that 99% of those who insist that 91 works better for them couldn't tell you what their compression ratio and boost pressure is. For that matter I doubt most of them know what compression ratio and boost pressure are, let alone how they relate to octane requirements.

[Gen13 F36]

Most people just drive and drive and drive. They don't pay attention to their car. For example, i saw someone with a flat tire....and drive in it for 10 miles maybe more. I saw some one drive with 3 cyclinder out of 4 working...they just drive. They don't know what is that sound coming from the engine... its just the engine running....they will never understand whats up.

[eluded]

Originally Posted by bimmer456

89=less power

Run 87 octane. It's cheaper

[amw896]

lots of damage....go back to the Honda civic forums if you cant afford the proper juice.

[eluded]

Originally Posted by amw896

lots of damage....go back to the Honda civic forums if you cant afford the proper juice.

I always run 87 octane with the cheapest tires I can find and always insure the car with the absolute cheapest provider possible. What could go wrong?

[chhappy7]

Originally Posted by eluded

I always run 87 octane with the cheapest tires I can find and always insure the car with the absolute cheapest provider possible. What could go wrong?

Don't forget! Oil change at a jiffy lube or something with non-synthetic cheapest oil!!

[Gen13 F36]

Originally Posted by chhappy7

Don't forget! Oil change at a jiffy lube or something with non-synthetic cheapest oil!!

Thats why first thing I do when buying used car...is get an oil change right away, even tho the dealer said its just been oil change as part of the 99 point inspection....lol

[Fuller]

Originally Posted by Billfitz

89= less power if your engine has a high enough compression ratio and boost pressure to make use of higher octane. Otherwise all you're getting for the extra money spent is a good dose of placebo effect. My bet is that 99% of those who insist that 91 works better for them couldn't tell you what their compression ratio and boost pressure is. For that matter I doubt most of them know what compression ratio and boost pressure are, let alone how they relate to octane requirements.

n55 compression ratio: 10.2:1
boost: 7 psi

Yes, it feels better with premium, and my fuel efficiency is better. One can provide data to back the improved fuel efficiency.

[eluded]

Mines 11:1 and I see peak boost at about 15-16 pounds

[brettbmw]

Originally Posted by blankito

I just don't understand people who buy expensive cars, often spend thousands on accessories and mods but get cheap on gas rating...

Honestly, I would never go lower than 89 since that's what is required. They say they recommend 91 so I put 91... Since I got a JB4 I always use 94 when available and 91 when there is nothing else

I do not have any numbers regarding power or mileage, but on most cars I had, I could feel the car ran smoother with the recommenced grade. Also, unless you drive 3000 miles per month, the difference between 89 and 91 will be only a few dollars per month so why take a chance?

TOUCHE...Like my father used to tell me if you can afford and expensive car you can afford to put the best gas in it...My wife and i both put mobile 93 in both our bmws...