Oil Capacity Question/Verification

[jfoj]

Agree, my 2005 6.0l is 6 quarts and has an oil cooler in the radiator. 275,000 miles on 5W30 and still hitting it daily. Think of this, my 2005 6.0l might get 14 MPG on the highway pushing it, but it is surviving, my 2024 gets close to 19+ MPG on the highway depending on how hard I am pushing it, but it is fragile based on the engine loading the TCM is putting the engine under. How many miles will these L87 be good for?? I doubt over 150k miles without major issues. Time will tell.

Agree that the oil sump was upsized to try and keep the 0W20 cooler and to balance fuel dilution and oil consumption.

But you also hit the nail on the head about oil warm up, more oil, more oil warm up time.

What we all have to live with these days.

Back to late 1960's maintenance.

 

[viven44]

Agree that the oil sump was upsized to try and keep the 0W20 cooler and to balance fuel dilution and oil consumption.

Finally have the scanner working on the 2024... Based on this evening's drive at 90F, our 2024 5.3L's oil temp was ~205F consistently after it warmed up and coolant was stuck at about 212F. It was a 30 minute mixed (city/hwy) drive. Oil pressure was ~25 PSI at idle and got up to about 60PSI driving or getting up on the throttle.

What was a bit alarming is LTFT was -25% to -30% on both banks at idle and would drop down closer to zero levels while idling. STFT looked good.. this was checked shortly after fuel-up so maybe some evap stuff mixed.

 

[jfoj]

What scan tool are you using?

One interesting difference between your 5.3l now that you can actually monitor the oil pressure is the 5.3l L84 has a single stage variable displacement oil pump. The 6.2l L87 has a 2 stage variable displacement oil pump.

You indicated you had about 25 PSI oil pressure at idle and about 60 PSI while cruising at highway speeds.

My 6.2l with 0W40 has about 35 PSI oil pressure at idle and about 45 PSI while cruising at highway speeds. It appears the 2nd stage of the oil pump is primarily triggered on RPM and not engine load in the 6.2l. Seems at around 3500 RPM the 2nd stage on the 6.2l kicks in and the oil pressure will jump to around 80 PSI.

This may be part of the 6.2l bearing issue, 0W20 oil at around 40-45 PSI while cruising on the highway at Low RPM and High Engine Loading. Seems to me that 60 PSI would a better value for trying to keep the bearings loaded with enough oil while under extreme loading to keep the oil wedge in tack. The 2nd stage oil pump trigger should be based on about 75% engine loading and not 3500 RPM.

And the oil pressure sensor measures the oil pressure at the REAR of the engine block BEFORE the oil is actually directed to the valvetrain and then to the bearings, front main bearing and front rod bearings being LAST in the oil distribution path. Seems it would be interesting to have an oil pressure sensor at the side of the engine block in the front near the front main bearing to see what is really happening to the oil pressure especially with the variable cam timing and DFM active! The camshaft is hollow and filled with oil to control the cam timing and the DFM has to take oil pressure and volume to collapse lifters, wonder what kind of craziness is going on in the oil distribution path in the engine with all kinds of components competing for oil. Is it like when someone runs the water or flushes the toilet while you are in the shower???

Who am I to think this is a problem???

GM trying to squeeze too many MPG out of the 6.2l.

 

[viven44]

I'm using a Thinktool Pro..

45 PSI seems OK on highway, but on the lower end. That would be a very aged engine by old school standards. I have a mechanical gauge on my old trucks. On the 460 BBFs that are high mileage and copper showing on the bearings, I'm usually 25-30 PSI at idle when hot, and ~55-70 PSI highway.

That seems like a reasonable hypothesis on why the 6.2L may be dropping more often..

 

[jfoj]

This may be one of the reasons the L84 5.3l has fewer failures, higher oil pressure at highway cruise. This along with the fact the 5.3l has less torque and the TCM drops gears to get the RPM up when compared to the 6.2l. I watch my 6.2l spike from 70% engine load to 90-100% engine load when pulling an ever so slight grade, 50-100 ft elevation change over 0.5-1.0 mile distance. Sometimes the transmission will downshift from 10th to 9th, but this is only about a 100 RPM increase. Maybe going from 1600 RPM at 100% load to 1700 RPM at 80-90% load.

I agree that 45 PSI on the highway with the extreme bearing loading the 6.2l encounters is not ideal, again this is 45 PSI measured after the oil filter and before the oil is distributed inside the engine oil galleys to the valvetrain and bearings.

I would love to see what the oil pressure is at the front main bearing oil supply path, this could be an eye opener.

 

[viven44]

I'll confirm oil pressure a bit more... when I got to the engine parameters I wasn't on the highway. I saw it hover around 48-50 PSI just coasting along with light throttle in the city... I'd imagine a highway light throttle cruise could be similar, although driving 70+mpg would have reasonably high RPMs where I'd expect over 50PSI (but when I got on the throttle it got up to 60 in no time.)

 

[blanchard7684]

Interesting findings @viven44 and @jfoj . Thanks for sharing.

The old rule of thumb was 10 psi for every thousand rpm.

Sommerfeld number for rotor stability is independent of supplied pressure. Stribeck is also somewhat independent of supplied pressure. (boundary and mixed lubrication mechanisms are when there is no oil flow).

Bearing cooling from convection heat transfer is highly dependent on oil pressure for getting the oil flow in and out of bearing to remove heat.

In some large industrial applications (compressors, gearboxes, turbines) there is a start up oil pressurization to get some "lift" to reduce boundary and mixed lubrication friction.

If any difference in oil pressure was suspected, I would have though 6.2 would have higher oil pressure than 5.3.

 

[jfoj]

I think GM tried to squeeze to much in the way of fuel economy out of the 6.2l and chose the 2 stage oil pump in order reduce pumping loss in the oil pump except when absolutely necessary. But interesting that GM engineers deemed the 6.2l to need 80 PSI of oil pressure under higher RPM operation, but were satisfied with 40-45 PSI when the engine is under severe loading at lower RPM, lugging!

With all the stupid Auto Stop/Start garbage (soon to hopefully be a thing of the past) I would have expected the manufacturers to put an oil accumulator with an electrical trigger or an electric oil pump like they use in the automatic transmissions to keep the oil pressure in the bearings during all these dry starts. For all that do not disable the Auto Stop/Start feature, I wonder how much they are aging their engine during all these repeated engine starts.

 

[viven44]

Ok based on the drive this morning the oil warmed up to ~200F after a good 20 mins or so and I recorded oil pressure vs RPM on the 5.3L. Ambient was 80F.

RPM Oil pressure (PSI)
550 24 (idle in drive)
680 29 (idle in park)
1000 43
1500 54
1900 58
2000 60
2500 65
3000 70

I want to say for 35-40mph drive the transmission stays in the 8th gear a while, and based on yesterday's data the RPM was around 1250, thus oil pressure would have been the 48 PSI I observed a lot. On the highway, coasting 60mph in 10th gear at around 58mph was exactly the same (1250 RPM, 48 PSI), but I'd imagine going 70mph would put me closer to 1700 RPM where I'd have over 55 PSI.

 

[jfoj]

@viven44

Thanks for the feedback.

You are seeing the exact same thing I was seeing, these engines need at least 20 minutes of DRIVING, not idling, for the oil to reach 200F and this is at ambient temps of 50F or higher, below 40F 30+ minutes of DRIVING.

The oil takes much longer to warm up if you just allow the engine to idle when cold started.

My mule has not had 0W20 since 544 miles, so I have no idea what the 6.2l oil pressure was with 0W20, I may be able to work with a neighbor on his 2025 before he dumps his 0W20 to get some 6.2l baseline oil pressure values.

With 0W40 in my 6.2l at 1500-3000 RPM my engine pretty much has 45 PSI of oil pressure.

It is only when the engine RPM tops probably 3500 RPM, I have not tested to see if 3500 RPM is the exact trigger point for the 2nd stage oil pump solenoid to trigger, but the oil pressure will jump to around 70-80 PSI. I believe the OBDII calculation for the oil pressure is actually a bit high in the one tool I was using to log the oil pressure, I have to revisit the calculation and adjust as needed.

The 6.2l has a 2nd stage oil pump test routine that operates sometime after the engine is started and will test the 2nd stage oil pump solenoid and you will see 2-3 spikes in oil pressure.

First graph shows the 2nd state oil pressure test shortly after engine start up, the spikes close together, then you can see spikes that are based on engine RPM while driving. NOTE, I believe what I graphed is about 10 PSI too high due to the OBDII calculation being off. So just mentally offset the line graph down by 10 PSI and this is probably a more realist oil pressure valve.

Second graphs shows 2 stage oil pressure test zoomed in. It appears that the test will not occur until the engine oil temperature reaches at least 100F and probably has to occur at idle or during lower RPM operation. NOTE, I believe what I graphed is about 10 PSI too high due to the OBDII calculation being off. So just mentally offset the line graph down by 10 PSI and this is probably a more realist oil pressure valve.

I will try to see if I can put together a graph with the Oil Pressure VS Engine RPM, I am sure I have logged this data and I just need to find it. If I find it, I will edit this post and add the graph for others to see how the 6.2l differs from the 5.3l with the single stage variable displacement oil pump.