15W-40 or 5W-30

[Dick]

I'm gona be hauling a trailer weighing around 12'000 lbs through mountains and desert were heat can be a factor. In these conditions what would be the best oil weight to use.I'm using Amsoil synthetic.

[slc]

IMO 15w-40 would provide the best engine protection for what you intend on doing.

[Kennedy]

While others may have had good results with the 5w30, mine were less than stellar. No real problems persay, but analysis showed more wear. If you want a 5w oil, I'd suggest Mobil Delvac1 5w40 synthetic. This oil is excellent in heat or cold...

[rjschoolcraft]

I've had good results with Shell RotellaT Synthetic 5W-40.

[Tough Guy]

Ditto on ronniejoe's statement...


Da Boy.

[TanM998]

No matter what you use, be sure that the oil is rated for a Diesel engine. If it doesn't have a diesel rating on the label, then don't even bother to put it in your truck. I have had no problems with SHell Rotella 15w40

Scott
'85 Tan M998 W/CTIS

[moedog]

MOBIL DELVAC 1 DIESEL OIL. NONE BETTER FOR ALL TEMPS. BE SURE YOU PUT MOBIL 1 SYN. IN DIFF AND MOBIL 1 SYN IN YOUR AUTO TRANNY FOR EXTRA PROTECTION.

[B1powered]

Amsoil has a 5W-40 you could use that would give the excellent cold flow(5wt) and high heat protection as well.(40wt)

[Jim Brzozowski]

Kennedy,

Did you just try 5w-30 in the winter or did you run it in the summer too? Wouldn't the 30 be a little light for the way you been known( so I've heard) to flog your engine on that superflow?

[Kennedy]

Actually this was well before I had my dyno, and before the Dmax really crossed 400 RWHP. In fact I believe most of the miles were logged driving to BC Canada for the Rendezvous. At that point, the Juice was the hot ticket, and wasn't even a true 90HP. I had 16,400 miles on the truck and the sample was taken in June. The Delvac 1 has done VERY well for me since then.

[Heartbeat Hauler]

Originally posted by Dick:
I'm gona be hauling a trailer weighing around 12'000 lbs through mountains and desert were heat can be a factor. In these conditions what would be the best oil weight to use.I'm using Amsoil synthetic. Well Dick, I don't think I would use any oil, syn or otherwise, in a 30w specification. Manual calls for 15w-40 or 5w-40. I think a good syn 5w-40 will do what you want, but I have used the Rotella 15w-40 for 32K miles without incident. This past winter I did use the Rotella 5w-40 just to ease the cold cranking.
JP

[dcalex]

I've been told, and it seems to make sense, that we should use the narrowest viscosity range that we can expect to encounter with our particular use. That with the new oils the additives that give the visosity variables are what is now most susceptable to breakdown where-as it used to be the oil itself that was most susceptable. The explanation was long and complicated and, to be sure, didn't predict the end of the earth if we used a wide viscosity range, but was a general guideline. What was most note worthy was that when they do breakdown, it's towards the light end since thats the base that makes up the oil.....the additives give it the viscosity variable toward the higher end. I don't pretend to be an expert on oil, but am passing this along just for you to use as you see fit.
I did get an opportunity to see this proved during last years fires here in Cal. I have a natural gas generator that ran for 10 days. The 10- 40 oil that I had been using in it broke down real quick with the heat of the generator. I changed it every 2 days and it ran out like water. Needless to say, that I now use the premium heavy service oil.