[silky1]

Hey I'm trying to do an oil change on my 2009 328i coupe but it looks like previous owner stripped or crossthreaded the oil drain bolt (oil is also leaking from the bolt), what size bolt is it so I can rethread it?

[PcarFan]

It`s M12x1.5

[e90yyc]

Make sure the washer is replaced (or at a minimum, present).

[mainbearing]

If the threads are all buggered up I wonder if tapping for a M14x1.5 drain plug can work.

[jsunma]

This may be more than the OP is looking to do/for, but before I got into retapping the threads on the oil pan, I'd make darn sure that the oil pan is in excellent shape and not something that is going to need to be replaced sooner than later...like mine was when it rotted clean through about 5 or 6 years ago.

[Efthreeoh]

It just simply amazes me how people can strip an oil pan drain bolt.

Is the oil pan steel or aluminum? If you have a gasket leak along with stripped threads on the pan, you may want to just replace the pan.

[Efthreeoh]

Originally Posted by jsunma

This may be more than the OP is looking to do/for, but before I got into retapping the threads on the oil pan, I'd make darn sure that the oil pan is in excellent shape and not something that is going to need to be replaced sooner than later...like mine was when it rotted clean through about 5 or 6 years ago.

True that. Mine is all kinds of ugly around oil sensor hole.

[mainbearing]

If the oil pan gasket needs replacing that will be a good time to swap in another pan, whether a used OE pan or a new aftermarket. Or have a machine shop professionally repair the M12 or tap to M14 at the time.

[NorthernDancer]

I had a Honda for about 21½ years. At about 10-12 yrs, I started noticing rust on oil pan. I kept a paint brush near the oil pan and used it, dipped it in the old oil, and brushed it all over any rust. Never thereafter, had any more rust on the oil pan.
One of the many advantages of doing your own oil changes.

[jsunma]

Originally Posted by NorthernDancer

I had a Honda for about 21½ years. At about 10-12 yrs, I started noticing rust on oil pan. I kept a paint brush near the oil pan and used it, dipped it in the old oil, and brushed it all over any rust. Never thereafter, had any more rust on the oil pan.
One of the many advantages of doing your own oil changes.

And maybe also an advantage of a car where the oil pan was not covered by underbody plastic shields. On my car, the original steel pan rusted through in a spot about 6" ahead of the spot where the drain plug was. I guess I hadn't found the opportunity to remove the shields often enough to observe and catch it.

Oh well, it would have been time to replace the oil pan gasket by then anyway.