The factory specs for oil in my 72 U code Cutlass Supreme is 10w30. It has a W30 cam and .030 over bore and just rolled over 101K original miles. With the mods done to the engine, should I stick with factory specs or switch to 20w50? At highway speeds, I get around 50 psi oil pressure, so I was just wondering...

Thanks,
Dave

 

sounds like its still healthy. the 10w30 would be my choice,

 

X2 - 10w30

 

Dave - 10w30. Are you thinking of using synthetic? BTW your oil pressure sounds healthy.

 

Nope...I use Valvoline VR 1 conventional.

 

Nice. That stuff isn't readily available up here. I'd have to use a different product like Lucas for Classic cars. Runs about $55 for 5 quarts up here. I hope you're not using a Fram oil filter. They're the cheapest least protective filter on the market.

 

No sir ..Napa Gold😀

 

You're probably O.K. where you are. Oldsmobile said that 20W-50 could be used down to +20F, and 10W-30 could be used down to +10F. The high temperatures and wear on the engine probably should also be factors. 5W and 5W-20 oils were not recommended for sustained high speed driving. If the viscosity increasing additives don't work you'll have the lower number. The VR1 & NAPA Gold seem like good choices. I've been using the 20W-50 or 15W-50 mostly because of the high temperatures encountered. I-10 gets hot in the summer, and it doesn't freeze here much any more.