Well, after a 62 mile run, from Katherine's Landing to Hoover Dam, I started with 70 psi and ended at idle with 69 psi. I am running Valvoline Racing (not VR1 Racing) part number VV851 sold at Napa only. It is 20/50 and seems to hold up well. BTW, the engine is a 466, 10/20 cut crank. It seems that alignhoning and quality Federal Mogel race bearings make this possible. I would change the oil and filter, what gas does to the oil, the oil will not recover. Get it out before you destroy the engine. Gas is not like water, water will burn off over time, gas does not.