Ok so i have read all of your posts and appreciate all the helpful advie given by all....so i guess i have 2 choices really: 1) would be to go out and pull all of my spark plugs and check for black soot on them (i recently replaced all my spark plugs last month so it would be easy to tell if they were coated); or 2) i could just start using the regular 20w-50 and monitor it and see how that goes for me. i personally am leaning more towards option number 2, as i hate messing with the plugs especially since the wire tends to slip off them while im driving....and i have such a horrible idle that i know a plug wire has come loose. i dont have that problem now, just when i first changed the plugs, dont know what it couldve been, but all better now. so i will just try the 20w-50, monitor it and if i have excessive consumption still, then ill pull the plugs and check.

Now, if it's a diesel you were talking about, it wouldn't matter so much because one way (15w40) or the other (diesel fuel), it's just fuel to the engine. It all compresses and ignites and propels the car. Maybe you could lean back the IP delivery if you knew you were getting a little enrichment from the valves. But I guess things could get crazy if you bleed too much in through valves, and get a run away.

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Cheers!
Scott McPhee

1987 300D