Quote:
Originally Posted by Purdy Swoft
I've used Rotella 15w40 in some of my model A's with no problem . I figure the 15 is a bit thin . I use Walmart 20W50 I figure that the 50 will better cushion the bearings on an eighty eight year old engine . I also use it in the professional rebuilt engine in another of my model A's .
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15w40 is only "thin" when the oil is cold which is a good thing because it flows to the bearings faster at start up. 15w40 oil doesn't stay at 15 when the engine warms up. When the engine is at operating temperature it is 40.