10w60? That's way too thick.

For an old engine, where you're not sure of the tolerances, 20w50 is safe... for newer performance engines, you'd go for 0w20 or 10w30... the smaller the range (the difference between the two numbers), the less additives in the oil and the better its resistance to breakdown... in fact, you can use straight 30 or straight 40 oil for the racetrack, but they're not recommended for road use.

10w30 or 10w40 is okay for daily use. 20w50 for older engines... all depending on the engine in particular. Engine safety first before extra performance. ;)