Quote:
Originally Posted by Bill Hamilton
They say the original Motorcraft 5W-50 shears down to a 40W in about 1500 miles and some are recommending the Amsoil 10W-40.
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All multiweights will shear down faster than a straight weight, you can't have your cake and eat it too. If its spring time in your area (its hitting near 90 here) then just use a straight weight diesel spec IMHO. If they have to add VI modifers to the oil for it to meet its multiweight spec those are the last things you want in your oil once its up to temp.
IMHO - forget the name on the bottle anymore unless its a race only oil as that is the real stuff for the track (and not for the street since it has near zero detergents in it) Most diesel specs have the antiwear of the race oil but also come with a ton of detergents which will keep the inside of your motor totally spotless I have found.