20w50 Brad Penn suits my race motor because I run it hot with fairly large clearances of .003 rods and .0035 mains plus high temps. I warm the motor past 210 for the start of the day and the oil temp goes over 200. I stage at 185 and the oil temp is still above 200 at the line. Injectors are VERY fat at idle but the heat boils off the alky that gets in the oil because Methanol boils at 149 degrees. Water boils out as well with no problems or milking ever.