Very High Mileage truck oil suggestions

[SirReal63]

I just picked up a 2003 Chevy 2500HD 4x4 for use on a farm. It has 297k miles on the LQ4 and purrs like a kitten. I do however have low oil pressure at idle (sort of common on these engines) and will be doing a flush and changing out the oil pump to a high flow Melling. My initial thought is to do an engine flush to ensure any oil galleries that may be restricted are clean, then do an oil fill, change the pump and run it for a few days and do another change to ensure it is as clean as possible.

I typically run Rotella T6 in my vehicles but there is a dizzying array of oils on the market and I am unsure which may be the better oil to run in this very high mileage truck. Is there an advantage to the High Mileage oils here? The truck does not leak oil or any other fluids, doesn't knock and still has gobs of power. (It was an old AT&T service truck and got excellent service) This truck will not see much highway use and will idle a lot and be run hard when not idling. I plan on using it to pull stumps, trees and pull a trailer. It will be used hard until it breaks then it gets a new engine.

BITOG is such an awesome resource, and I figured if anyone had the best advice, it would be here.

 

[gfh77665]

I would not stress at all about this. Use a quality conventional (PYB, Mobil, etc.) for 3000 or 1 year, HM type if you wish, and a good filter...DONE. No need for flush & drain, etc. 297 is not crazy high mileage. These trucks go 250-300K easily. Relax and drive.

 

[Ramblejam]

Originally Posted By: SirReal63
I typically run Rotella T6 in my vehicles


There's your answer.

 

[901Memphis]

T6 is fine but T5 should work just as well for a flush cheaper.

 

[SirReal63]

Thanks, actually the only stress is over the low oil pressure at idle, hopefully the high flow pump will help. I know the engines last if taken care of, and this one obviously was. I have zero complaints with the Rotella, it served my E38 BMW very well.

Now the tough question, what weight would be recommended? I understand the clearances have diminished with this many miles so perhaps a thicker oil may be called for? We really don't have a winter here, no polar vortex fun.

 

[GutsyGecko]

I would use the T-6 you use for everything else.

 

[Ramblejam]

Originally Posted By: SirReal63
Now the tough question, what weight would be recommended?


Rotella T6: 5w-40

 

[gman2304]

I'm guessing you don't have too many $$ in an old AT&T service truck that has almost 300,000 miles and probably been hammered all it's life. Considering you're in TX, I would use any conventional 15w40 HDEO and call it a day.

 

[gfh77665]

Originally Posted By: SirReal63
I understand the clearances have diminished with this many miles so perhaps a thicker oil may be called for?


They have actually grown with wear, not diminished. But I think thats what you meant since you are considering bumping up a grade or so. BTW, welcome fellow Texan, to this board.

 

[SirReal63]

No I don't have much in it, a rebuilt LQ4 will cost more than what I have in the truck, so I do want to get as much life from it is as possible. An interesting thing, there is still some paperwork logs on the truck, it appears the same person used it from day one.

The body has no dents, scratches or blemishes. The interior is in excellent condition and the steering is tight, no loose feeling you typically find in high mileage vehicles, no rattles or thumps in drivetrain. It still has the BrandFX topper and Dimensions power inverter in it. Overall it was a score. Even if I do end up dropping a new engine in it, I am way ahead. Yes, the tolerances have grown, my brain is still fuzzy this morning. I am not in S/A any more, I moved way north to Marble Falls.

Gentleman, I appreciate the advice, I will stick with the Rotella and try the 15w40, if it doesn't help the pressure I will do the pump. It will feel good to get my hands dirty again, being semi-retired I like projects.

 

[bubbatime]

Originally Posted By: gman2304
I would use any conventional 15w40 HDEO and call it a day.


I agree. I wouldn't run a synthetic oil in an engine with 300K miles that has probably had dino in it since day one.

My first choice would be a 10W40 high mileage oil such as Maxlife/Defy followed by my second choice of 15W40 HDEO.

 

[Oil Changer]

Skip the flush and pump and just run the T6.

 

[901Memphis]

15w40 wouldn't be a bad idea.

 

[clinebarger]

Put a new O-ring on the pick-up tube & change the oil pan gasket, The oil filter adapter is part of the pan, So the pan gasket seals off 2 main oil galleys. LSx engine tend to leak at both locations at high mileage. I see it as maintenance item.

Changing valve springs is also a good idea at that mileage, Dropping a valve is bad.

 

[SirReal63]

If I understand correctly, on the 4WD you have to drop the front end out of the truck to pull the pan. When/if I have to go that route then I will drop in a new long block with the Melling high flow unit. Dropping the front end is more than I can do at home so trying this first. Hopefully the problem is reduced flow from sludge and the flush will help. If not then it is off to the mechanic.

 

[clinebarger]

It's not that hard, Lower front diff. with a jack. Don't completely remove it. Remove the front driveshaft, Electrical, & diff. to frame bolts.

What is the Oil Pressure?, You just say "low".

 

[SirReal63]

Normal idle is about 20, sometimes it drops to 5 for a second or two then climbs back up about 20. Hwy it runs between 25 and 30, it has never hit 40 that I have seen. The engine runs smooth, has very good power with no complaints from me other than the oil pressure that shows on the gauge.

I have been playing with engines since the early 70's and have never had one consistently low like this. The gauge moves around a lot but doesn't bounce around like a bad sending unit would do. Even when the pressure shows dangerously low, like 5, it has never sounded starved for oil. No tapping, no grinding or any other impending disaster sounds. I know those, I have heard them before on cars with a failing oil pump.

I did the flush and the oil that came out did not look that bad, so I don't think it was sludge. I found no evidence of metal in the oil, the drain plug but haven't cut the filter open yet. The 15w40 HDEO didn't make a difference in pressure. I may go ahead and replace the sending unit, it is cheap and easy.

 

[3311]

20 psi at idle is to low for an LS engine IMO. The 7 psi to float the crank idiots have never operated an LS engine at 7 psi for any period of time. I would verify that psi with a mechanical gauge and if it is 20 psi I would replace the oil pump with a melling m295 for stock flow or a 10296 high volume. These gearator pumps wear. Twice the rpm of the old cam driven pumps and an aluminum housing vs cast iron. Not to mention the hardened bypass valve can get stuck. They are a wear item and should be replaced when the water pump goes since you are already half way there IMO.

Here is mine from the 04 below in which the bypass valve was stuck open and starved the engine. I was only at or below 20 psi for a very short period of time. http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/2849535/2

Edit: The remaned LQ4 in the 04 below with 3500 miles on it below is at 40ish psi hot idle with a ported m295 and a light xw40 mix. The 06 below is at 32ish hot psi original pump with T5 10w30. I also prefer oversized xg3675 or Pl25288 filters.

 

[SteveSRT8]

No way to be sure since the factory gauge and sender is ALWAYS suspect first.

Verify the pressure, then get started after you know what you are trying to fix!

Despite the above poster's stuck bypass it is very uncommon, note that GM makes over a million of these engines a year. We have had ONE and only one do this. All gerotor pumps wear, that is not a new phenomenon.

Interesting that in our fleet we rarely replace water pumps anymore, even out to beyond 250k miles. The last van we sold had over 500k miles on it with no oil consumption, no leaks, no smoke, no knocking. While they are not all that good some of us need to learn to maintain our engines a bit better perhaps?

I have also ran a 6.0 equipped 3500 Savana for years that never exceeded 30 psi and idled very close to the point where the spark is cut!

 

[SirReal63]

Gentleman I appreciate the thoughts. An interesting development, I have been researching the numerous issues people have had with these engines and low oil pressure. Sometimes it's the sending unit, sometimes a stuck relief valve, sometimes the pump and sometimes the screen under the sending unit getting clogged and showing low pressure. I wish I had access to the service records on this thing, the water pump is obviously new, still shiny and clean and new washers on the radiator shroud, so I know it has been opened up before.

I began to suspect the screen in the manifold under the sending unit. I still have several quarts of Kreen so I put half a quart in, ran the engine to temp and watched the oil pressure climb and climb. It has stopped dropping below 20 and runs at about 40 at 2k rpms and at low idle is staying about 25. I suspect that as the Kreen is burning off it is also cleaning that screen enough to let the true oil pressure hit the gauge.

It is the current theory I am working on. I find it interesting that the motor flush did not do the trick and half a quart of Kreen is seemingly doing it, almost immediately. I will continue to monitor it and will report back.

I still want higher pressure, especially on an engine with this many miles on it. My favorite mechanic is leaning towards s short or long block, but I suspect that is his answer because it gives him money, and eventually he will be right.

Has anyone ever replaced a 6.0 with a 5.3? 6.0's are kind of hard to find ($$$ too) and 5.3's seemingly grow on trees.