About 7K miles ago, I rebuilt the engine on my '89 Corvette. It used a quart of dyno oil every 450-500 miles (compression is fine on all cylinders) when using 10-30 or 10-40 oil. I'm now using Valvoline Racing 20-50, have 250 mi. w/little oil used (less than a 1/2 pint). Would I be ok to go to synthetic (20-50?) at this point? I eventually want to switch to syn., but don't want to until oil consumption is minimized even though I put in a very aggressive cam, etc.