My cousin had Mobil 1 0w-40 sheer down on a trip in the summer across Arizona in a turbo Volvo 850. The combination of oil temp rise and oil pressure drop caused the a/c to be shut off in a black car at just under 120F. He changed back to his usual oil, 5w-30 Red Line while in Phoenix and the analysis showed the Mobil 1 to be a thin 20 weight with some higher than usual wear metal readings. I know that he does not spare the whip but you can bet he won't be using a 0w-40 ever again. He never has problems with the RL 5w-30 so there is something to be said for paying a little bit more and getting a good oil. He actually changed the oil at a friends place as he said to avoid more damage, but I'll bet it was to make sure the a/c worked.
Thin is Better: The Gospel According to A.E. Haas
- Thread starter Jim Allen
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But a turbo'd gas powered Volvo is very, very far from a medium and heavy duty diesel engine that I think this thread was probably concerned with. I don't think the issue has ever been will the oil thin/shear. I'm more concerned about under what conditions will a diesel have issues with a thinner oil, whether from operating conditions or an oil that was a low viscosity to begin with. Certainly a gas engine has some of the same issues when discussing oil viscosity and operating conditions, but they have a different use and different designs/equipment so it's really not totally applicable in this thread.
JA, I don't think there is chart as it would be far to arbitrary to be of much use. There are several places that have viscosity calculators where you can plug in the viscosity at 100*c and at 40*c and it will extrapolate the viscosity at other temperatures. I've done this for several oils I run in my personal vehicles, and another reason why I run the pan heaters even during most of the summer.
JA, I don't think there is chart as it would be far to arbitrary to be of much use. There are several places that have viscosity calculators where you can plug in the viscosity at 100*c and at 40*c and it will extrapolate the viscosity at other temperatures. I've done this for several oils I run in my personal vehicles, and another reason why I run the pan heaters even during most of the summer.
"Kerosene that is fully additive formulated may make a good oil."
LoL, best quote ever!
LoL, best quote ever!
Thinner oils WILL result in reduced oil pressure and thinner oil films in the very high pressure regions of the valvetrain and ring/cylinder interface. However, powertrain engineers can design engines to run successfully on very low viscosity oils by:
1) Reducing main/rod bearing clearances
2) Increasing the oil pump output
3) Installing a thermostatically controlled oil cooler
4) Employing roller elements in the valvetrain to change the lubrication conditions from sliding friction to rolling friction.
5) Increasing sump capacity to moderate peak oil temps under high temp/high load conditions.
Folks who think you can just arbitrarily use low viscosity lubes in every application simply don't understand much about tribology....This is why you don't see me giving out free medical advice...
TD
1) Reducing main/rod bearing clearances
2) Increasing the oil pump output
3) Installing a thermostatically controlled oil cooler
4) Employing roller elements in the valvetrain to change the lubrication conditions from sliding friction to rolling friction.
5) Increasing sump capacity to moderate peak oil temps under high temp/high load conditions.
Folks who think you can just arbitrarily use low viscosity lubes in every application simply don't understand much about tribology....This is why you don't see me giving out free medical advice...
TD
I used Esso 0W40 for a full 7500 miles earlier this winter. I drive mainly city with my 06 Cummins and 7500 is the severe service interval. I found when the oil was freshly changed with it it ran nice and smooth- but later on closer to the end of my interval it started to sound a little less so. I think the oil is great, but only for the intervals suggested by the OEM. Hence, my switch to Amsoil. I want something that I don't have to be wondering "is this oil going to stand up to 7500 HARD miles, with lots of cold starts, idling, stop and go and high rpm's?" Amsoil gives this reassurance. I still think for what it is generally used for, the Esso is a fantastic oil.
Down to the basic. The oil has to be thick enough to protect in the most demanding operations you will encounter but not too thick as to cause a power loss .
I think the article takes a bit of a narrow approach, although it does explain different weights very well.
The one part where "engine clearances change very little" is absolutely untrue. In a 302 Ford, you run 5 thou piston/wall clearance which is actually a decent amount. If you run lower, you run the chance of scuffing the skirts because they expand too much for the bore. Remember aluminum expands almost twice the rate as iron.
Even the clearances in the oil pump, main bearings, rod bearings, and especially the wrist pin change. This MUST be taken into consideration.
The one part where "engine clearances change very little" is absolutely untrue. In a 302 Ford, you run 5 thou piston/wall clearance which is actually a decent amount. If you run lower, you run the chance of scuffing the skirts because they expand too much for the bore. Remember aluminum expands almost twice the rate as iron.
Even the clearances in the oil pump, main bearings, rod bearings, and especially the wrist pin change. This MUST be taken into consideration.
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