My gas cap says to specifically use 91 octane,I have been using 89 and rarely 87 and notice a little knocking?

Question

I have a 05 BMW M3 and I hope that I am not damaging the motor? I still use 91 but not as often do to the price.

Answer 1

you are, you need to use 91 or you may end up needing a new engine. that is a high performance engine and only should be using 91.

Answer 2

Um, i had a 2004 BMW M3. you NEED to use 91 octane gasoline on them. You can't even use 89, if your using anything else, your engine is retarding the timing in order to compensate, that reduces performance, gas mileage, and wears down the inside of the engine down a lot faster. You NEED to put premium in an M3, the engines inside these great machines definitely need 91 octane to run properly, its probably one of the last engines you wanna be using 89 on, and ESPECIALLY not 87.

The knocking is obviously gonna happen with lower octane gasoline, but in an M3 if your not using 91 octane, the effects are hidden, until your engine gunks up or wear itself down so much that problems start to occur. If you keep filling up 87 or 89, you're going to wear that engine down sooner and you'll be facing problems (EXPENSIVE problems) sooner than you think. M3 engines are not cheap to work on, i know from personal experience.

91 octane is not that much more expensive, its like 10 cents a gallon more. That's not that big of a difference, and it will save you from a very expensive repair bill. Also, you own an M3! come on, you have to be able to afford that extra .10 cents a gallon, if you can't, the M3 isn't the right car for you. The engines in them are strong and powerful, but at the same time they can be very delicate, and a good way to ruin one is to constantly use 87 or 89 instead of 91.

Remember, there's a reason why BMW marks on the car to use only 91 fuel. If you tell the BMW dealer you were putting in 87 octane, they'll probably think your nuts.

Answer 3

Geez! just use what the cap says.

You think you're saving money by using 87, but all you're doing is s******g up the car.

Answer 4

use the 89 and put some octane booster in it.

Answer 5

So you are saving less than $2 a gallon to risk doing slow damage to your overpriced engine?  Wow what do you do with that $2? Does it really help with all your other bills?  I wish I would have thought of that.  That's another $8 a month for me.  Imagine what I could do with that.  I hope your motor blows.

Answer 6

This is exactly why I stick to North American made cars.  Some do offer similar performance advantages as a BMW, but will run on regular octane fuel and will usually get better gas mileage.  As a bonus, repair bills are cheaper.

Answer 7

well...

you can use octane booster as a supplement but that is really  just a oil/acetone mixture and it's not really recommended

car says 91 use 91

goodluck

Answer 8

you have an expensive car and it will cost many thousands of dollars when your engine has to be replaced because of your penny pinching!

Why did you do this?

Answer 9

Engine knock is very dangerous to your engine.  It will destroy your engine from the inside out.

But your car should have a knock sensor to prevent that.  So if you still hear engine knock, have the knock sensor checked out.

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And go back to 91.

Good Luck....

Answer 10

This happened to me once (the knocking); I had to go back to using the higher octane. I suggest you do the same. It's a bummer with the high prices & all, but it's better than walking. Have you considered trading it?