I really enjoy a good oil thread occasionally. FWIW, I have learned through the years as long as you use a good quality oil, change it often with a new filter, you can expect long engine life. I try to stick with synthetic but synthetic can be classified into different groups.
Amsoil is a group IV synthetic - a true synthetic as opposed to the group III synthetics on the market like Shell Rotella 5W 40. I have used Amsoil in the past but I don't like the way it is marketed - too hard to get. Plus, a few times the Amsoil had to be sent back by UPS because a bottle leaked in transit to my house. Recently, I have been using Shell Rotella 5w40 which is frankly formulated for diesel engines. My engine runs incredibly smooth with it and the price is right - about $16 a gallon at Wally World. I was a little hesitant to use a diesel rated oil but I haven't had any issues with it. No sludge, nothing. I change it according to the oil service light indicator and am always amazed at how clean it comes out after several thousand miles. I even use it in one of my motorcycles and it does well but thats a different story.
One thing about additives to your fuel: I SWEAR by Marvel Mystery Oil. Every so often I will put a few ounces into a full tank of gas and I believe it has helped keep the injectors clean after 167,000 miles. Plus, my car seems to perk up / be more robust. Maybe it is just perception but I know for a fact running MMO in my motorcycles makes a vast improvement in throttle response.
Oh yea, I use the Mobil 15W 50 in my inline four sportbike and I have found nothing that comes close to performing as well. The transmission shifts slick as butter and the engine runs a bit cooler in the summer which is good for an oil cooled engine with 16 valves that operate at high rpm most of the time. I swear by it but haven't used it in the BMW yet. Its sort of expensive compared to the Shell Rotella which I am very satisfied with.
1998 528i - sold 222,000 miles
1998 540i - sold 159,000 miles
2007 328i Coupe - 30,000 current
Last edited by ozarkmark; 06-15-2007 at 12:16 AM.