Approved oil for BMW E46's
If you are like me your free BMW maintance has expired and you're on your own. The biggest thing you need to worry about is probably the oil.
The service indicator in the car wants you to change the oil every 13-15K miles depending on driving style, but, I find that a little long. Full synthetic oils are better than standard mineral oils pumped out of the ground, but, it's not so much the break down of the oil that I'm concerned about. It's contaminance causes by metal wear, blow by, etc. As these engines get along in miles the piston rings are naturally going to let more crud past and into your oil. I like changing my oil and filter inbetween the normal service intervals or at about 7K miles just to keep the oil cleaner. It's not scientific, but, it doesn't hurt.
The following only applies to non-M cars. So the next question is what oil to use? BMW recommends BMW High Performance SAE 5W-30 Synthetic, P/N 07 51 0 017 866. This stuff runs $6.06 per quart over at ECSTuning.com, plus shipping and the E46 uses about 6.5 quarts. You don't have to use the BMW oil if you don't want to, but, make sure you use BMW Long Life rated LL-01. What's this? Well first, not all 10W-30 oils are created equal. The 10W is the oil viscosity when cold and the 30 is the oil viscosity when hot. These really only define a range of viscosities, not the actual viscosity. So don't grab a case of Mobil 1 10W-30 and assume it's BMW Long Life rated. It's not! The only Mobil 1 oil that is rated LL-01 is the 0W-40. While the 5W-30 won't instantly kill your engine, it won't provide the level of protection that BMW engineers designed the engine for. For the US Market there are four oils that are approved for use, but, some of them will be next to impossible to find at your local auto parts store so use whichever one you can find.
List of BMW Long Life rated LL-01 oils in the US market:
Mobil 1 SAE 0W-40
Castrol Syntec European Formula SAE 0W-30 (Look for Made in German on the bottle)
Pennzoil Platinum European Formula Ultra SAE 5W-30
Valvoline SynPower SAE 5W-30
For BMW E46 M3's use:
Castrol TWS Motorsport SAE 10W-60 Synthetic Engine Oil
Castrol Formula RS SAE 10W-60 Synthetic Engine Oil (BMW P/N 07 51 0 009 420)
Here is a memo published by BMW. BMW USA approved engine oil
For more information there is an excellent discussion on the E46Fanatics.com web site as well as on bobistheoilguy.com
For the oil filter use only the BMW original P/N 11 42 7 512 300. I've heard that it is the same as the Mann filter, but, also heard that the Mann filter is more prone to break apart and should be replaced in between normal service intervals (7K miles) where the BMW filter will last the full 15K miles. They cost about the same so might as well buy the BMW original.
Interesting forum threads.
E46Fanatics thread with pictures of insane sludge build up
Another E46Fanatics thread with a lot good information (just read the first post)
Another insane example of sludge build up on a E39 540i (scroll down to post #33)