I mistakenly put 87 octne fuel in my tank for my BMW 325ci - I usually put 93 octane in it. Will this damage my engine - the tank was .25 full before I put in the lower octane gas.

No worries. It will do no harm.

Thank you!!!

Your engine will start pinging as soon as the high octane in the lines is burned off, which won't be long. You will also find that the computer retards the timing to stop this, and the timing will retard so far that the car will barely run, will have little power and will burn gas like a road warrior. Add octane boost now, and then at the 3/4 tank mark, top up with the super-high, 94 octane, or what ever the highest is you can get. Do that for a couple of times, and then go back to your normal grade of fuel. At the price of a replacement engine, it is better to take no chances on causing damage.

Cheap fuel wont hurt it at all poor performance is all and crappy mileage

All that say poor performance or poor mpg if you use a lower grade gas are incorrect. There has been thousands of test proven that higher octane is a gimmick and only required if you're going to the race track.

My 2006 e90 325xi does not like regular. Error code excessive timing retard. Some stumbling like a bad plug resulted. Added 108 octane It still stumbles off and on. But pulls stronger between stumbles. Any ideas? Havent driven very far so maybe thats the problem. Check engine light off but timing retard did show. Will check again shortly. I suggest dont burn regular.

It wont damage anything if you put some lower octane fuel in the tank so long as you dont do it all the time, and avoid aggressive acceleration. Some vehicles which are recommended premium can actualy opperate fine with reg, but will have a small reduction from it peak potential performance. If the owners manual says premium is required or can only be fueled with premium then that instruction should be followed to avoid knock or detonation. Since its a newer BMW you might notice some slight knocking and reduction in performance. The knock is due to the 87 octane fuel igniting before primary ignition is supposed to occur. 91 octane has a higher flash-point, and will hold off igniting till a higher pressure is reached in the cylinder. Turbo charged vehicles like your BMW 3 require a higher octane fuel to prevent knocking due to the higher cylinder pressures in your engine. DO NOT USE OCTANE BOOSTER, its a waste of money and isnt going to help. I think BMW actually recomends against fuel additives in the owners manual. If you notice any knocking its best to just drive easy, get down to a quarter or half tank and refuel with premium. Eventualy after refueling enough times the avg octane of the fuel in your car will get back to where it should be.

Guru5YS7K, Sometimes it takes the computer awhile to recalibrate, even after the correct fuel is in use. Should go faster if you put in Premium, and drive easy till the computer recognizes knocking is no longer occuring. Just a guess but did you add alot of octane booster to achieve an overall 108 in your tank? If so its better to just refuel as you burn off the lower octane fuel.

I put unleaded to my x3 and usually i put premium, it says yhere i can put unleade sas long as more than 10%ethanol, i put regular in costco then after some driving it becomes shacky, is there a promlem with the engine?? Or. Do i need to empty it and put premiolum again

I put 87 instead of 89 . Is gann happen to my car damage please answer me because I am so scary