Ok, so we hit 115 F yesterday in Scottsdale AZ. My freshly built GPR engine was running at 11 psi at idle in Drive when I exited the interstate after driving for about 30 minutes. I'm running 10w/40 and wondering if I should go to a more viscous oil. Thoughts?

 

I run 20w/50 during the summer when it gets really hot here in Arkansas. Haven't had any problems. I know some guys around here that run 20w/50 year round.

 

I ran 20/50 when I lived there and it does make a difference.

 

If I recollect correctly, the Disco manual recommends 40 weight for up to 105 degrees.

50 weight may be advisable in your case.

 

Yeah, I'm thinking 20/50 is probably a better option here. I was kinda surprised that interstate driving actually seems to make the oil hotter than city driving. Anyone else notice a similar trend?

 

Sorry, I was off on my recollection. Here is the quote from the 2003 Disco Owner's Manual (page 229):

Engine oil temperature ranges

5W/30 will protect from -22ºF (-30ºC) to 95ºF (35ºC).
5W/40 will protect from -22ºF (-30ºC) to 122ºF (50ºC).

10W/40 will protect from 14ºF (-10ºC) to 122ºF (50ºC).

 

Well, it may well hold up to 122 F, but 11 psi at 115 F is a little too close to comfort for me. Maybe I should move north? : )

 

I run 15w/40 (RotellaT) year-round. When I lived in KY and here in FL.

 

You're the one that has to drive it. If it makes you feel better running a higher weight then run it. Plus if you have an oil gauge which I'm assuming you do, then give 20w50 a try and if you don't like your numbers then change back.