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New to me, and my first diesel, a LMM. Now the question... It is a 2008 with only 26000 miles on it. When it is cold and I start it up, it has 60 lbs on guage of oil pressure but when warm it drops to below 1st mark on guage unless at highway speeds then just above 1st mark. Is this normal?? My Avalanche starts and maintains 50-60 all day long. Just wondering is this a trait of a diesel or not?
:help
 

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If using synthetic oil, yes this is normal, around 30psi when hot, 60 when cold.
When changing oil, you will notice famous typewriter rattle (especially when cold),
it will fade away with the oil getting contaminated with exhaust particles ...

Next time, use the search function here on this forum, is been mentioned more than once..
 

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I think its normal regardless of synthetic. I run a mineral 15W-40 and when hot, it idles below 30. Oil pressure is a function of two things, given all things in the engine are equivalent--oil viscosity and oil temperature (and engine speed, obviously). All 15W-40's have to fit into a viscosity window (otherwise they would some other vis grade), and being able to see differences on the OEM gauge is very difficult. One thing to note on the LMM though, since it does active dpf regeneration, you'll get a little bit of fuel dilution over time, which will lower the viscosity of the oil. I've seen several percent, but one of the GM engineers who was very intimate w/the Duramax said it was designed to withstand 12% fuel dilution..........which it a shi#$ load! I suspect thats why they don't recommend 10W-30's, since after several % of fuel dilution, the viscosity approaches the 10W-30 range.

I'm in the engine oil industry and work with test engines and OEM's pretty frequently, so this stuff is interesting to me.
 

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Hi there,
Just changed over to Amsoil 15-40 yesterday and now hear this rattle you mentioned in your reply to a seperate question.
I have a 2007-5 LMM Chevy 2500HD is this noise normal ? Also i am getting 20 psi oil pressure at idle and 60 - 70 driving conditions ..is this also normal?
thanks
 
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