454 older engine, summer months,75 f. been using 20w-50 castrol gtx, just wondering if it is to heavy, maybe 10w-30 no problems so far, any recomdations.Thanks

I used 20-50 in my 396 in the summer in the north east from 1978-summer 04 and no problem as of yet. If your worried about it maybe try 15-40 if you like to wind it up faily often as it still protects well in the heat of summer because thoses BBC do tend to run a little hotter than your avg SBC.

I figure the little heavier oil can protect against thermal breakdown when the motor is hot and you decide to twist it up to 5500-6k+ rpms for a little fun or run with those heavy rods & pistons tugging hard on the crank as it spins. A thinner oil could possibly allow a rod bearing or 2 to lighly touch the crank in high rpm situations as would way too heavy of an oil do too like straight/single grade 60-70wt oil would do on a cold day.

But there may be many opinions on this topic so if your motor is old with some miles on it 20-50 & 15-40 are fine in the summer but if its a fresh motor with the bearing clearances on the tighter end of spec i would not run 20-50,i would run 10-40 or 14-40 max and not 20-50 untill you have 5k-10k miles on it or after a few summers of getting into the throttle a lot if thats how you run it to loosen it up a bit brfore going to the heavier visc oil.

Scott

thanks scott just what i needed to no,as i said no problems, just thought it might be to heavy

I always run 20/50.