Wrong gas in my m45 oh no !!!!

[chrism45]

I bought a preowned 2006 m45 and have been putting 89 and not 91. Its had 89 unleaded for about 5,000 miles. Questions are do i switch? How do i switch? Should i takr it to the dealer for a flush of wrong gas? I dont know. A friend said he heard some knocking sound when i started the engine after the car had been parked and off for atleast over an hour. Advice, i love my car and what to keep it at its best performance level.

[Poirot]

Just change over to premium on the next fill-up. The ECU is self tuning and will slowly adjust as the octane level increases as the percentage of 89 is burned off. I don't recommend you run the car till E lights up before you fill.


Poirot

[chrism45]

Thanks, So what about the light knocking? ?? Shouldn't worry about it?? I dont hear it when im driving.

[Mjkkb2]

I would get it to half tank and then fill up with premium. I would go to half tank again and do it one more time. after that I would just go to normal filling routine, whatever your's is. You may hear some knocking, even your engine light may come on but as you keep diluting the low grade with better stuff it will go back to normal. No worries.

[CPJ LB]

Just fill up with Premium....now you have a great excuse for a long road trip.....drive the lower grade out

[audtatious]

Yeah, just switch to the grade you want. You could always reset the ECU and let it relearn with the new gas.

[rics8]

Well if have you have about 60 bucks to blow.

I would wait til your low/empty fill with 91/92/93 (your state) and add some fuel injector treatment like chevron/STP/ etc. drive.
The ecu with self correct for the fuel. but in the main time check the knocking.

[ZiggyM16]

Slight engine knock is a normal occurrence on most any premium fueled vehicle ran on lower grade fuel along with loss of power and performance. As stated by other members simply reintroduce premium fuel into your car and you should be fine.

On a side note never put regular gas in a premium only car as it defeats the purpose of its design. Not implying you were trying to cut corners im just saying.

[zerg711]

Not to scare the OP, but slight knocking led to 2 engine replacement due to 1 of the cylinder failures which resulted in me lemoning the vehicle.

I don't think the knocking is a fuel grade issue. You should probably check your oil levels.

[The00Dustin]

IIRC, the 2006 M45 manual says something to the effect of "Lower octane fuel can cause damage and should only be used in the vehicle in an emergency (/ if no other fuel available). If lower octane fuel must be used, drive gently until it is mostly gone (/ more than one tank)." If you have the manual, you can find the proper wording, if not, follow the advice above about taking it easy and working the lower octane fuel out (I'm not too concerned with whether you do it over multiple tanks or run it past E and then put in some 92 or 93). Note that from what I have read elsewhere, octane booster is a joke and will not even boost, for instance 89 to 89.5. I can not vouch for that statement, but I tend to believe it is correct.

[svard75]

Not to scare the OP, but slight knocking led to 2 engine replacement due to 1 of the cylinder failures which resulted in me lemoning the vehicle.

I don't think the knocking is a fuel grade issue. You should probably check your oil levels.

That wasn't due to poor gas grade though right? I believe your knock was oil starvation related right?

[CPJ LB]

Not to scare the OP, but slight knocking led to 2 engine replacement due to 1 of the cylinder failures which resulted in me lemoning the vehicle.

I don't think the knocking is a fuel grade issue. You should probably check your oil levels.

That wasn't due to poor gas grade though right? I believe your knock was oil starvation related right?

another possibility is running a lean fuel mixture...there are lots of modifications out there that increase air flow to the engine, but not everyone tunes their cars appropriately...so the chances of running Lean is increased...then over time, the engine consistently knocks...then the engine is on a path of destruction....