1990 928 S4
I changed the oil today. It's not difficult, but I hear people having trouble with it, so I took some pictures. The hardest part is removing the bottom engine cover (plate). On my 81 I don't need to remove it, so I didn't know it was a big deal to change the oil on the S4.
I let the engine run a while to warm the oil, but not too long. I then drove the car on to the ramps and raised the back.
The bottom cover is held on by 10 8 mm hex head screws, 2 10 mm screws, and 2 10 mm bolts. There are 4 screws across the back, 4 across the front, 2 at the front corners on an extension piece, 2 near the back up inside a recessed area. Once all the bolts and screws are removed the cover slides towards the front of the car and pulled down.
I removed the oil cap (top front of the engine), then crawled under the car to remove the 15 mm oil drain plug. I had a large catch basin under the drain hole to collect the oil. Make sure it's big enough, there's 8 quarts of oil in the engine. Once all the oil was drained out of the engine, I removed the oil filter (located to the front of the oil drain), again collecting the oil in the catch basin.
When the oil stopped dripping, it reinstalled the drain plug. I made sure to use a new washer and not to cross thread the bolt. I then filled the new oil filter with oil (about 2/3 full) and put a thin film of oil on the rubber seal. I then installed the new filter. Putting the oil into the filter saves the engine from running without oil during the first start up.
I then added 7 quarts of oil, checking the oil level after the 6th quart. At the 7th quart, the level indicated 1/2 quart low. I then started the engine, and ran it for a few miniutes. I check under the car to make sure no oil was leaking from the drain plug and oil filter. I then shut off the engine, and checked the oil again. This time it indicated 3/4 quart low. I added the 3/4 quart and checked again.
The engine cover was a little dirty, so I hit it with some engine degreaser before I reinstalled it.
The whole process took a little over an hour.
Copyright 2000, George A Suennen