100 HP flathead what oil?

With all oil recommendations aside I am surprised to see that many flatheads that have 100 HP (or is it just imagined HP?) :):confused:
 
It's always funny when someone asks what oil to use. Basically any good quality oil will be fine. Unless you built 10 flattys and filled them with 10 different oils and then arranged for every engine to be driven in exactly the same way for 5 years, and then tore them all down and scientifically checked all the parts could you then say if one was better than another.
And even then there would be enough "noise" from other considerations (material defects in a component etc) that it would put the results in doubt.

Just buy something whose name you have heard of, fill it up and drive it. Life is too short to worry.

Mart.
 
Back in the 50's there was only about 300 ppm of ZDDP and our engines survived just fine. I think most oils today have around 800 ppm.
 
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