I can say that when changing oil at 3500 miles, the oil is shearing below the expected viscosity grade. So start with 0W20 and run it for 7500 miles and have some fuel dilution, your guess is what you end up with. I would love to see an oil sample from an early 6.2l failure under 5k miles with the factory oil fill. The bearing loading due to the Torque output of the L87 really exceeds the protection that 0W20 can provide when cruising on the highway, carrying cargo and passengers and towing. Leading is spiking upwards of 95% without downshifting below 8-9 gear. The TCM is holding the gears and using all the engine Torque for fuel economy.
Daily driving around town 0W20 may be acceptable, but the trend is every failure seems to be happening at highway speeds when the engine loading tends to be the greatest.
5.3l L84 do not have the high failure rate for 2 specific reasons:
1. The engine does not produce as much torque and the TCM software does not keep the engine heavily loaded on the highway, it allows earlier downshifting.
2. While the 5.3l L84 and 6.2l L87 have the same base variable displacement oil pumps, the 6.2l L87 has a 2 stage control solenoid that limits oil pressure based on RPM, not engine Load. The 2nd stage higher pressure of the 6.2l L87 oil pump trigger appears to be 3,000 RPM, these engines rarely run at these RPM's unless someone is harder into the throttle, normal highway cruising the engine rarely tops 2,000 RPM.
The main and rod bearings are last in the lubrication path and #1 main and front rod bearings are furthest from the oil pump. With DFM, ASS and oil controlled cam timing competing for oil volume and pressure the bottom end gets the short end of the stick and is likely loosing oil pressure and volume while the lifters are using oil for DFM control and the cam timing is being controlled. .
I would run nothing thinner than 5W30 in these engines and if there was an easy way to increase the oil pressure, I would do it. I think you could unplug the 2nd stage oil pressure solenoid, but I am sure it will trigger SES/CEL/MIL and it may impact the DFM if not disabled and even then it could be an issue. Installing the 5.3l L84 oil pump would be the best option, but again what does the ECM do if the oil pressure is high, who knows. Not sure if the 5.3l L84 has the same preload spring in the oil pump as the 6.2l L87 oil pump.
GM screwed up and should have oiled the bottom end first on these engines, but this would have been a tooling cost, at a bare minimum they could have used Teflon coated rod bearings like they did in the much earlier engines this may have saved a large percentage of engines, I am pretty sure GM did use Teflon coated rod bearings in the earlier L86's but I could be wrong. They are running Teflon coated main bearings in these engines still due to ASS due to the crankshaft and torque converter weight on "dry" or non hydrodynamic bearings for all the ASS engine cycles.
Anyway a proper design and no cutting corners running hydraulic fluid in the engines and both GM and the customers would have been much better off!
Not convinced the next generation of engines is going to be much better, time will tell, but I would not want the next generation engine until 3-4 years after deployment.
