I had my engine rebuilt last year, and after I had it done, it burned
oil. When I go to the drags and check it after a night of racing, I'm usually down 2 qts. This is about 90 miles time. Prior to rebuild I was using Royal Purple 21
oil. I switched to Pennzoil 20w-50 racing and kept using it, because it's way cheaper than putting in RP the way this thing was burning
oil.
About a month ago, I was going to the drags, and wanted to change the oil. The Pennzoil is so dark and heavy, I wanted to put a light colored oil in, so I could see how fast the oil changed color. I put in Quaker State 10w-40, only because they didn't have what I wanted. Nice golden color going in. Went to the drags, made my runs drove home. Checked the oil level the next day and it's on full. The engine builder's theory is that the other oil was too heavy and the rings didn't wipe enough off, so it was burning it.
I don't know if he's right or not....Only know I don't burn oil anymore. Next change RP will go back in and see what happens.