Originally Posted By: dnewton3
I think we need to clarify the question here, or more specifically, understand that there are actually two questions likely being addressed:
1) what is a safe temp for the ISX
2) what is a safe temp for the lube
I don't know enough about the operational parameters set into the PCM for the ISX; someone else will have to help out here.
As for the lube, 250F is in no way unsafe. Even a conventional lube can provide a good performance if the base stock is of good quality. I believe an ideal temp would be 200-225F; most would agree about that. But a little spike in oil temp is not going to grenade the engine nor the lube. Even long sustained runs are tolerable. If you were to approach 300F in the sump, I would be concerned. But not at 250F.
And just for reference, before any of you go off half-cocked and say I'm nuts, I'll offer this bit of information ...
In the infamous GM filter study (881825), they ran the DD-60 engines at full load, with the sump at 250F for the entire duration of all the tests. Eight hours at a time. Repeated several times. On conventional lube from 1988.
And while we also would agree that massive oxidation insolubles are a bad thing, I'll remind you all that some amount of high-heat oxidation is actually a good thing, because it promotes the TCB (tribo chemical boundary layer) formation on the part wear surfaces. Or have you all forgot about SAE 2007-01-4133? This anti-wear layer of oxidation byproduct is actually a good thing, and is bolstered by higher heat. Once it is established, wear rates typically drop precipitously by and order of magnitude to near-zero levels (a direct quote from the study).
Several years ago, I flogged my Dmax pulling our RV through the Rockies and into the desert southwest for summer vacation. I let the sump get as low as I could tolerate on the dipstick. I ran that engine with no mercy in regard to throttle; if I wanted to move, I floored it, at times for minutes on end in uphill pulls out of the valley floors and over ranges. I am sure the turbo temps got hot; the EGT was maxed at OEM limits around 1300F countless times on the trip. And when I got back, and pulled the UOA, everything was completely normal; totally within specs for both the wear metals and the lube conditions. All on dino 10w-30 Rotella TP.
Is there a reason to fear lube degradation? Sure. But not at 250F.
Great details.
I note as well that no one specifically spoke to the fact that the oil temp varies quite a bit by location within the engine. So sump temp might be 250, but oil in the heads or other hot spots may be quite a bit higher in temp...
I think we need to clarify the question here, or more specifically, understand that there are actually two questions likely being addressed:
1) what is a safe temp for the ISX
2) what is a safe temp for the lube
I don't know enough about the operational parameters set into the PCM for the ISX; someone else will have to help out here.
As for the lube, 250F is in no way unsafe. Even a conventional lube can provide a good performance if the base stock is of good quality. I believe an ideal temp would be 200-225F; most would agree about that. But a little spike in oil temp is not going to grenade the engine nor the lube. Even long sustained runs are tolerable. If you were to approach 300F in the sump, I would be concerned. But not at 250F.
And just for reference, before any of you go off half-cocked and say I'm nuts, I'll offer this bit of information ...
In the infamous GM filter study (881825), they ran the DD-60 engines at full load, with the sump at 250F for the entire duration of all the tests. Eight hours at a time. Repeated several times. On conventional lube from 1988.
And while we also would agree that massive oxidation insolubles are a bad thing, I'll remind you all that some amount of high-heat oxidation is actually a good thing, because it promotes the TCB (tribo chemical boundary layer) formation on the part wear surfaces. Or have you all forgot about SAE 2007-01-4133? This anti-wear layer of oxidation byproduct is actually a good thing, and is bolstered by higher heat. Once it is established, wear rates typically drop precipitously by and order of magnitude to near-zero levels (a direct quote from the study).
Several years ago, I flogged my Dmax pulling our RV through the Rockies and into the desert southwest for summer vacation. I let the sump get as low as I could tolerate on the dipstick. I ran that engine with no mercy in regard to throttle; if I wanted to move, I floored it, at times for minutes on end in uphill pulls out of the valley floors and over ranges. I am sure the turbo temps got hot; the EGT was maxed at OEM limits around 1300F countless times on the trip. And when I got back, and pulled the UOA, everything was completely normal; totally within specs for both the wear metals and the lube conditions. All on dino 10w-30 Rotella TP.
Is there a reason to fear lube degradation? Sure. But not at 250F.
Great details.
I note as well that no one specifically spoke to the fact that the oil temp varies quite a bit by location within the engine. So sump temp might be 250, but oil in the heads or other hot spots may be quite a bit higher in temp...