Just picked up a new to me 2019 L5P Duramax. The vehicle had just been serviced and oil changed with 15w40. Started the truck yesterday morning (it was 12* outside) and oil pressure at idle was 110 psi. I'm assuming that 15w40 oil doesn't like to flow very well and is very thick at that temperature. After a couple minutes of driving, pressure dropped to 30 psi at idle. My question is this, owners manual calls for 5w40 or 15w40 depending on temperature conditions. Will switching to a 5w40 vs the 15w40 make that much difference is cold start applications ? People in my area that own diesel trucks have said to go to a 10w30 year round and call it good. They recommend either Mobil Delvac Extreme 10w30 or Rotella T6 10w30 if going that route. What are you guys thoughts on this.....
L5P Duramax Oil
- Thread starter VAB
- Start date
If you don't drop below 0 degrees, you'll be ok, can always plug it in to help too.
I just usually run 5w40 year round so I don't have to worry about it and it starts easier. Not to mention easier on the batteries when cranking as well.
I just usually run 5w40 year round so I don't have to worry about it and it starts easier. Not to mention easier on the batteries when cranking as well.
It'll make some difference in 12f. I'd skip the 10w-30 and use 5w-40 year round instead. Mobil 1 Extended Performance 5w40 is a great off the shelf oil so get that. But using a 15w-40 with a lower cold crank figure helps but the temp must be the same. Can't compare a 5w to a 15w since 15w is tested at -20c and 5w is -30c. What oil is in it exactly.
Mobil 1 Delvac extreme is 6100 mpa CC
Delo xsp is 4600 mpa CC
Valvoline full synthetic heavy duty diesel is 4200 mpa CC
Lower is better in cold cranking.
Mobil 1 Delvac extreme is 6100 mpa CC
Delo xsp is 4600 mpa CC
Valvoline full synthetic heavy duty diesel is 4200 mpa CC
Lower is better in cold cranking.
Last edited by a moderator:
Stick to the owners manual on the L5P and use either 5w40 or 15w40.
10w30 is an option with the 2016 and older Duramax engines, but I see no point experimenting with thinner oils in the L5P.
10w30 is an option with the 2016 and older Duramax engines, but I see no point experimenting with thinner oils in the L5P.
Most likely some AC Delco since I bought from a GM dealership, it has an AC Delco filter on it too.
Pressure is higher but flow is still there. I wouldn’t worry too much but give the oil a minute to warm up a little and get everywhere it needs to go. On our jets we have 4min warmup. Does the same thing. We get a spike in oil pressure and it takes a couple minutes to drop down into the green then we’re good for takeoff. This is with oil temps down to -40c. Don’t floor it right away and should be good. Do a used oil analysis on your oil to put your mind at ease.
- Joined
- Mar 10, 2021
- Messages
- 251
Normal. Oil pressure relief valve will open at 104-114 psi.
Similar threads
