Re: Oil weight for drag racing/street use
I am 'old school' believer in straight weight oil. My recommendation is straight 30W, or if you prefer multi-viscocity then go with 10-30 (my preference is Valvoline) and see how your oil pressure holds up when the engine is warm. 20-50W is too thick for any application, especially a new engine, in my opinion.
To answer your question, yes high viscocity oil will use up some horsepower - but not a whole lot. Think of the difference of stirring molassis as compared to stirring water. Now the volume of open space between the oil pump gears and is not very much, so the drag won't be very great. But the force necessary to transfer the oil through the pick-up screen, tube, etc will be significantly greater with the higher viscocity oil.
64 Chevelle Malibu Sport Coupe (original owner) car now has 427" BB, Jerico 5-spd. trans., Dana 60 rear end.
SAE Member (25+ years)
ASE Master Certified Engine Machinist
AERA Certified Professional Engine Machinist