Correct fuel for 1992 525i M50 Engine

[Al Gray]

I am having a debate with my son over the correct fuel to use for the car. Since the M50 engine has 10.0 to 1 compression ratio shouldn't premium gas be used as opposed to regular. Premium always runs better but he wants to pinch some pennies because of rising gas prices.

[Blitzkrieg Bob]

I am having a debate with my son over the correct fuel to use for the car. Since the M50 engine has 10.0 to 1 compression ratio shouldn't premium gas be used as opposed to regular. Premium always runs better but he wants to pinch some pennies because of rising gas prices.

I use the mid grade in my M50tu and the S38, I think it's 89 octane.

[Torque]

Owners manual and the inside of the fuel door says premium for the m50 525i. I don't see why you would go against manufacturer's recommendations.

[Blitzkrieg Bob]

Owners manual and the inside of the fuel door says premium for the m50 525i. I don't see why you would go against manufacturer's recommendations.

I remember mine as going by the octane.

87 = regular

89 = ?

92 = super

I'll have to check again

[Dave M]

Owners manual and the inside of the fuel door says premium for the m50 525i. I don't see why you would go against manufacturer's recommendations.

Always regular 87 octane

Never a ping, don't even know what one sounds/feels like. Always 30+ mpg on long HW hauls. Why spend more. Oh, in Canada, if that makes any difference.

Dave M

[Dr. evil]

i use 90 oct. when i use anything less i notice that i have to push the pedal harder for accel.

[Morgenster]

I use 98 octane (European denomination) or 100+ octane when on LPG.
So what's that in US octane ratings?

[Sam-Son]

the minimum for the M50 is 89. 91 with any kind of chip

[94_e34_525i]

The m50 has knock sensors so it really doesnt matter what fuel you put in it....unless you have a chip (which changes the timing) so you need 91...but 87 89 91 93 all work in the m50 (stock chip) it all depends on what performance you want...

[duby55]

Premium unleaded[90 AKI or 95 Ron] for my 91 525i with the M50. I've ran both regular and premium fuels in my car and it does run better with premium fuel. I fear higher maintenance issues from running regular fuel, so I prefer to spend more for better fuel that could save me from having idle problems, shorter spark plug life ect..