[The X Men]

I noticed that the 2012 535i has a min. octane requirement of 89, have anybody compare the difference in performance and gas mileage using 89, 91 and 93? Its only 10-15 cents a gallon difference, but if there is no difference in performance and gas mileage, I might as well use 89 octane.

[gicamuci]

89 is the minimum required since E34 if I remember right. But then 1% of owners are reading the manual or the sticker on the gas door. I am using 91 only because here in Canada they add ethanol to 87 and 89.

[valcor535]

My 2011 535 ix has a label (on gas tank door) that says 91 octanes premium is required....

The owner's manual tells you:

Required fuel
Super Premium Gasoline/AKI 91 or AKI
89
BMW recommends AKI 91 or 89.
Gasoline with lower AKI
The minimum AKI Rating is 89.
If you use gasoline with this minimum AKI Rating,
the engine may produce knocking sounds
when starting at high outside temperatures.
This has no effect on the engine life.

[The X Men]

Originally Posted by valcor535

My 2011 535 ix has a label (on gas tank door) that says 91 octanes premium is required....

The ownerd manual tells you:

Required fuel
Super Premium Gasoline/AKI 91 or AKI
89
BMW recommends AKI 91 or 89.
Gasoline with lower AKI
The minimum AKI Rating is 89.
If you use gasoline with this minimum AKI Rating,
the engine may produce knocking sounds
when starting at high outside temperatures.
This has no effect on the engine life.

My gas door saids 89 AkI. So which octance do you use, 89, 91 or 93 and is there any difference in performance and gas mileage?

[Tuesday]

All octane really means is - the higher it is the more compression the fuel will sustain before detonation. The knocking noise is called pre-detonation, and this is when the cylinder is so hot (and compression so rapid) that the fuel explodes before the combustion cycle and this can cause major damage to your motor. The piston/rod assembly is only meant to take the force of an explosion at TDC and anything that gives it negative pressure beyond standard compression cycles puts a lot of components in danger like rods, rod bearings, rings, and crank bearings. You 'can' get away with lower octane ratings since these engine are so de-tuned, but consider this the equivalent of putting 4 spare tires on your car: it will work but when you really need your car to do what it was designed to you may find yourself out of luck.

I am sure since they put such a low minimum requirement for these cars that the knock sensors are great at immediately reducing timing for safety sake - but just because you can eat McDonalds every day and technically survive....would you? I highly recommend everyone with a turbo to run 91 octane minimum as these motors are not cheap to replace.

[The X Men]

It seems to me that BMW change the gas door label from 91 AKI min on the 2011 535i to 89 AKI min on the 2012 535i. Does anybody know if they just change the label or did they retune the engine or software to run on lower octane.

[JNoSol]

The compression of the 2012 N55 is 10.2:1, which is very high for a turbo engine. It's not worth saving a few pennies, just gas 91+ to be safe. Gas in the U.S is way too cheap to cut corners.

[fafafoooey]

I would think if someone was cheap enough to use anything other than premium, the engines would detune (lack of better term) to not cause damage. I might be misinformed, but that is what I had read with the E60s. Might not apply to the F10.

[The X Men]

I dont think its a matter of being cheap or not, it a matter of rather using any octance above the min. requirement will yield increase performance and efficiency. BMW lower their min. requirement on the F10. The big question is did they change the engine somehow, software or hardware wise. I know that when other car companies lower their octane requirement, they rated horesepower and torque also was lower. This is not the case with BMW.