My 1998 528i has 115,000 miles. I just bought it last week and noticed that the last oil change was 4,800 miles ago. I'm planning on doing the change myself at 5,000 miles. The guy at Autozone steered me towards Mobil1 15W-50 Extended Performance, saying the thicker oil was better for a car with as many miles as mine. I searched the boards here and found most people using 0W-40 but with no mention of the miles on their cars. I also found people cautioning against using the thicker oil on BMWs. So I have conflicting reports and want to clear this up before I drop an inappropriate oil into my car. Suggestions?

The thicker oil would be indicated by high oil consumption, or certain mechanical noises, not high mileage. You don't really have high mileage.

So if the car is running fine right now I should stick with something thinner? I'm looking at the car's service records and from what I can tell, here is what was used previously:

09/17/04 5W30 Synthetic
06/06/05 5W30 Synthetic
11/16/05 10W40 (doesn't say if synthetic or not)
05/12/06 10W40 (doesn't say if synthetic or not)
02/12/07 15W40 (doesn't say if synthetic or not)

Look in the owner's manual.

Look in the owner's manual.

+1

115k is not high milage for a BMW. Don't worry about it. I have 220k on one and 240k on the other, and they both run perfect.

Use the viscosity specified in the manual, and make sure it meets the BMW LL-98 or LL-01 spec. Change it when the service indicator says to, probably between 10 and 15k miles. If you can't find a LL-xx oil, use anything with the right viscosity and change it at about half of what the service indicator says, or around 5-8k miles.

Mobil1 0w-40
Castrol Syntec 0w-30
Valvoline Synpower 5w-40
Amsoil 5w-40

I think any of the above would do just fine. All of them have the BMW Longlife 2001 or 2004 rating.

I would concur with bimmerZ5. 115k is not high milage IF the previous owner has not abused it in some way. If after your first oil change interval, there is little to no oil use (assuming you do not have a leak) then you still have a tight engine with lots of life left to it. If that is the case then the BMW LL-98 or LL-01 spec oils are perfect. M1 0w-40 is a thin 40 weight that is an excellent oil and perfect for winter us if you need a 40 weight. (maybe if you have a little consumption) Castrol 0w30 only if is says "made in Germany" on the bottle. A great all year oil. If you like 5w40's and you have NO consumption, Mobil 1 truck and turbo is an outstanding oil too. I have used it and M1 0w40 (in winter) in my '98 540i for about three years now and the engine is spotless and uses no oil at 125k.

I am a little more conservitive on my intervals though and would suggest more like a 6k to 8k change even with synthetic oils.

15w40's are usually not synthetic and are usually diesel oils. By the way, do not ever ask a guy who works behind an Autozone counter about oils. Go to bobistheoilguy.com and learn it for yourself. You will realize how much BS and myth is out there about oil.

I am a little more conservitive on my intervals though and would suggest more like a 6k to 8k change even with synthetic oils.

I change synthetic at 10k (easy to remember) and send it to Blackstone labs. There is always life left in the oil, 15k would be do-able IMO. But I agree, it's better to err on the side of caution.

Go to bobistheoilguy.com and learn it for yourself. You will realize how much BS and myth is out there about oil.

+1

actually, an additional thought here... over 100K miles, many of these engines will have a valve cover gasket leak. you can find out my pulling your ignition coils and looking down the spark plug well and see if there's any oil. if so, this is a great opportunity to open up the valve cover and see what your engine looks like (at least the head portion) inside. Replacing a valve cover gasket is relatively easy and gives you a view of the "insides" so you can better assess the situation considering that you may not have all maintenance information from the previous owner.

if you do find some sludge, consider auto-rx. you can read more about it at bobistheoilguy.com (BITOG).