diesel engine oil seems to be failing at 5000 mile

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ive got a 1995 series 60 detroit i bought used.miles unknown.until last month the oil pressure was constant at 51 pounds when warm.it might drop a little when id pull a hill.suddenly its dropping below 48 and when it does my engine gets hot.i had an engine oil analysis done that showed good viscosity and normal metal wear.i changed the oil and the overheating went away.another 5000 miles and the same thing is happening to rotella 15-40.just to see what happens i added a fresh gallon of oil.the pressure and temp returned to normal.500 miles later im back to the same problem.with no evidence of contamination or failing engine parts im perplexed
 
Delo has a huge following here. Every truck I ever drove had it including detroits like yours. But I never paid THAT much attention to the oil pressure. As long as it was where it should be I drove it. Never seen any oil related failures myself.
 
When I switched to Delo my consumption dropped from Rotella. Reminds me to tell the new owner of my 91 Ford 250 diesel to not fill all the way to the top of the dip stick.
 
While i'm not a diesel mechanic, i have to wonder if you are having an intermittent overheating condition. Perhaps its not a 3psi drop in oil pressure causing the overheat. It might be that you are seeing the psi drop as a result of the engine getting hot and that affecting oil viscosity.

I really don't think oil pressure going from 51 psi to 48 is going to cause over heating.
 
Originally Posted By: spasm3
While i'm not a diesel mechanic, i have to wonder if you are having an intermittent overheating condition. Perhaps its not a 3psi drop in oil pressure causing the overheat. It might be that you are seeing the psi drop as a result of the engine getting hot and that affecting oil viscosity.

I really don't think oil pressure going from 51 psi to 48 is going to cause over heating.


Above sounds plausible, but just in case it is oil related (which you do seem to have circumstantial evidence for) perhaps you could try topping-up with a comparable straight weight 40?

Perhaps in Minnesota you can't run a straight weight through the winter, but topping-up should be do-able.
 
How many miles are on the engine. I guess it once was rebuilt. When your engine gets hot the oil pressure drops ? What does the factory recommend for oil pressure?
 
i have no idea how many miles its got.its served me well for two years.im leaning towards fuel dilution.the oil analysis done by speedco states its ability to detect fuel in the oil isnt very good.btw the engine doesnt smoke except for a small puff on start up.one mechanic i spoke with yesterday suggested lucas.his theory is if its worn bearing the lucas should stabilize it if it doesnt i need to find a better lab to tell me whats happening to the oil
 
First of all, stay away from the Lucas. Lucas has never solved a problem in the universe, other than allowing shady used car dealers to bump up oil pressure on worn out engines to sell a clunker. It's not going to do any good for your engine. There's nothing in your oil that needs to be stabilized, and Lucas doesn't stabilize anything aside from the company's market position.

Secondly, it sounds as if the overheating is knocking down the oil and not vice versa. Think about it. If something was going so wrong with your oil that your engine were overheating (which would have to be through friction), your engine would be dead.

Heat shear is real. I watched my old boat overheat one time. This engine, which always puts up 40 psi under any circumstances, dropped to 25 psi at 2500 rpm.

You need to be looking at why your engine overheats. It isn't because of your oil. Refreshing your oil makes it less prone to heat shear, but it isn't your oil doing this.

If you insist on pursuing an oil remedy, try Schaeffer synthetic diesel oil. Schaeffer and Amsoil synthetic oils usually deliver solid reductions in engine oil temperature in our experience, and the experience of others.
 
I have multiple Detroit's running Schaeffer's 5w40 at hot idle I see about 21 to 25 psi on the engines varying 200,000 to a million miles. It's starting to warm up outside obviously rinse out the radiator air-to-air and condenser with a hose. When was the last time the thermostats were replaced, it is my understanding that the oil cooler has a thermostat as well, what is your oil pressure at hot idle, what do you consider overheating
 
Btw my oil temp runs 190 degrees always. Truck never gets over 200 degrees.

My factory thermostats had 1m miles on them, huge difference in temp after replacement
 
I think youre looking at the oil instead of the overheating. I would start with a good oil analysis right after I went through the cooling system including the thermostats, they are relatively easy to replace. Does the engine have a coolant filter in the system ?
Every S60 I ever dealt with was pretty easy on oil.
 
Delo may have a huge following here, but I am not one of them. My 2000 S60 12.7 hates the stuff. Tried it for a while and got UOA's I really didn't like. My S60 has a preference for Schaeffer primarily or Delvac sometimes. I typically use 10w30 in winter and 15w40 in summer. Both syn blends.
 
Sounds to me like your coolant is overheating, allowing the oil to run hotter, thereby putting it at a lower viscosity. I don't think that a 15w40 will be sheared in a heavy-duty diesel.
 
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