Morepower, Jan article on synthetic oil; a turbo oil ?

[Hubert]

Jim,

In your recent article talking about synthetic vs conventional oils you mention something like the turbo adds 80F to oil temperature.

Do you mean a turbo charged vehicle will see 80F higher avg oil temp vs naturally aspirated everything else being the same.

Or do you mean the oil coming out of the turbo drain line will be 80F above oil going into turbo.

Either way thats a pretty substaintial increase.

I have measured oil pan temps on a small diesel at the 250F range when at max load. If you figure thats an overall avg mixed turbo drain and bearing drain etc the oil coming out of the turbo might be 265-280F or more during hard work. That is getting on up there in temps.

More evidence that oil grade and cooling is pretty big deal on a turbo diesel.

I can remeber exactly but near piston crown I have read oil temps soar upwards of 400-600F. I guess thats just for a short time though.

Another reason to let EGT's cool before shut down - the piston is really hot too (besides the turbo). I guess the block helps dissipate the heat after shut down and maybe why you get an increase of ECT after shut down and flow stops. The size of the block acts like a big ole heat sink and oil lives but at the turbo its different the exhaust side is really hot after working hard. Boost side can be hot too. So shut down immediately after hard work is really hard on oil.

[More Power]

Do you mean a turbo charged vehicle will see 80F higher avg oil temp vs naturally aspirated everything else being the same.

Or do you mean the oil coming out of the turbo drain line will be 80F above oil going into turbo.


Your second statement is what I was referring to.

Overall, the amount of oil circulating through the turbo is just a small fraction of the total circulating through the rest of the engine. And, the 80F statement is the full-load heat rise in a generic turbo diesel application, and is a ballpark figure for the 6.5. We rarely run our engines at full load for any length of time.

Oil temperature is a concern, but given the number of years the 6.5 has been traveling the highways, lubrication failures really haven't been a big factor. I've heard that the engineers at AMG designed the oil pan for the new P400 to have the capacity is has because of oil temps. When discussing modifying the pan for on-road duty, they suggested mods that maintain (as much as possible) the original P400 pan capacity. But again, this is for a worst-case use situation. HMMWV's are run very hard, pulling heavy GVW's and sometimes in deep sand.

Jim