High mileage motor thicker oil?

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Allen4rmGromLak

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I have been using the cheapest 10w30 and 10w40 I can find for the past 300k miles. Engine has 540k. Desperately needs to be pulled and rebuilt. But I'm running about 20 psi at warm idle and about 40-45 psi at freeway speeds. My factory guage reads higher, so I go off my aftermarket guage
 

Cheap Heap

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I did switch to Rotella 15W-40 in my 93’ with 292k on it. It was burning a lot of oil with an embarrassing amount of blue smoke out the exhaust with 5W-30. With the 15W-40 Rotella I’m burning 1/2 qt every 1,000 miles and I’m not seeing any blue smoke in my rear view at every stop sign anymore. Oil pressure is in line with what you’ve posted. I didn’t notice any pressure change with the different oil.
 

rcm9364

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The owners manual for the 5.7 Vortec lists two oils. The factory recommendation is 5w-30 but lists 10w-30 as an option for warmer climates. Mine is higher mileage as well so I like to run a bit thicker so I go with the 10w-30. But you can also run a bottle of Lucas high mileage with either oil for thickness/added protection.

P.S. your oil pressures are within normal limits for the engine.
 

Schurkey

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Do the TBI's have higher oil pressure?
My 95 k2500 HD 350 has 250k and the factory guage has it at 40 warm idle and 60 drivong.
The earlier oil pressure sending units are notoriously failure-prone. They have faulty seals, and fill with oil. They sometimes "slosh" when removed. They can fail and show abnormally high pressure, abnormally low pressure, or wild swings in oil pressure. At any rate, I suggest putting a real gauge on your engine to verify the true oil pressure.

I don't know if the '95 uses that same sending unit (bigass silver canister just above the oil filter, sticking out on the end of a brass ~80 degree elbow. The aftermarket replacements have a green stripe on them. They're sold under multiple brand names, but they're all made by the same factory.

http://www.automotiveforums.com/vbulletin/showthread.php?t=1136624
 

Supercharged111

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How high ppm does it have in zinc and phosphorus? FWIU if you get too high of a concentration, it'll plug your cat.

I doubt it's zinc and phosphorous content exceed what was allowed back when the TBI was new. Most high mileage oils are only one or two specs old. Even the oils with higher content are only high relative to today's standards. That and diesels have cats too.
 

Ehall8702

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317k, run 10w-30 , idle at 20psi hot. Don't burn any or use any besides the damn filter/cooler assembly leaking some ( 1/2qt between oil changes so I'm not stressing it yet, rust prevention is all that is).
 

evilunclegrimace

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I've been running Mobil1 10w-40 since the new Mr Goodwrench long block was installed over 17 years ago, doesn't burn or leak any oil in 5000 mile intervals. I did blow the head gaskets a couple years ago and when I rebuilt the top end, my pressures @ idle went from ~12-15 up to ~20-25, maybe because of the cam journals?

That would be correct IF you changed your cam bearings OR had a cam with worn journals and installed a new cam.

To many people associate low oil pressure with worn main bearings and completely over look the cam bearings. If the cam bearing are worn the mains are going to have less oil being fed to them.
 

Schurkey

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1. ZDDP "zinc and phosphorous" are way over-rated as anti-wear additives. This was deliberately induced by the cam companies twenty + years ago.

2. How does ZDDP poison a catalyst...unless the engine is an oil-burning pig?
 
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