just wanted to no if i wanted to switch my oil from 10/30 to 20/50 would that bebad from my camaro. 95 lt1 with 170/000 miles. i heard that 20/50 is good if your engine rev really high just wanted to know.

 

castrol gtx 20w50 is the only oil i use. sick

 

It is probably OK for your engine, being that with 170K, the clearances should be pretty loose by now. 10W40 may be a better choice come winter. The oil vicosity you need is dermined by the way the engine is built. If you have an engine that is built for racing using wide bearing tolerances to lessen friction, like Sick has, then 20w50 is needed. However, if you are talking about a new car built to very tight tolerances, 20w50 will be too thick and suffer vicosity breakdown as it gets squeezed through the tight clearances. Also, on a cold start the heavy oil does not flow well and parts tend to run dry a bit longer than if lighter oil was used. As for high RPM operation, you need the proper viscosity, but even more important you need an ample volume of oil to maintain lubrication and to cool things down, especially the valve springs.