L98 high-mileage oil

[WreckWren]

It'll likely be bleeding pressure off in the cam bearings.
Only step up to a 10w-40.
Going higher will just slow the oil down from getting to the lifters and rockers.

Yeah I'd sooner replace bearings than go higher than 5w-40 with OEM lifters, have heard many stories about the OEM lifters hating thicker oils.
I'd imagine the main bearings have also worn a bit, it's done a lot of Ks.

 

[shane_3800]

Yeah I'd sooner replace bearings than go higher than 5w-40 with OEM lifters, have heard many stories about the OEM lifters hating thicker oils.
I'd imagine the main bearings have also worn a bit, it's done a lot of Ks.

The lifters don't care, it's if enough flow, not pressure gets to them.
I've found most times the cam bearings in the alloy blocks go over 3 thou which is too much and let's too much oil bleed out, dropping the pressure down in the lifters.

 

[WreckWren]

The lifters don't care, it's if enough flow, not pressure gets to them.
I've found most times the cam bearings in the alloy blocks go over 3 thou which is too much and let's too much oil bleed out, dropping the pressure down in the lifters.

Yeah the cam bearings are a known weak point in all-OEM LS motors. That said, mine are performing fine (no strange noises or behaviour), and oil pressure is within spec, so not going to mess with it. No doubt the motor will need work before 400k just from sheer age, will deal with that then.

 

[shane_3800]

Yeah the cam bearings are a known weak point in all-OEM LS motors. That said, mine are performing fine (no strange noises or behaviour), and oil pressure is within spec, so not going to mess with it. No doubt the motor will need work before 400k just from sheer age, will deal with that then.

You won't notice anything, other than what you have described, this is because an engine oiling system is a series of controlled leaks.

 

[WreckWren]

You won't notice anything, other than what you have described, this is because an engine oiling system is a series of controlled leaks.

Correct, and of course as bearings wear you will see a gradual decrease in pressure. The key thing is to make sure to catch problems like prematurely wearing bearings before they fail.
A great way to do this is to have your oil analysed. This has been done for this motor. The wear components in the rotating assembly are wearing as expected for the mileage.

 

[shane_3800]

Correct, and of course as bearings wear you will see a gradual decrease in pressure. The key thing is to make sure to catch problems like prematurely wearing bearings before they fail.
A great way to do this is to have your oil analysed. This has been done for this motor. The wear components in the rotating assembly are wearing as expected for the mileage.

No, you can't just assume an oil test will pick this up.
My theory is that due to heat cycling the cam tunnels relax.
This in turn will let the bearings open up a thou or two which wouldn't show up in a oil test.

 

[WreckWren]

No, you can't just assume an oil test will pick this up.
My theory is that due to heat cycling the cam tunnels relax.
This in turn will let the bearings open up a thou or two which wouldn't show up in a oil test.

We're now at a point where there isn't any unusual behaviour from the motor, nothing strange has been in the oil, and there are no strange noises - I'm gonna leave the cam bearings alone for now. Cheers.

 

[shane_3800]

We're now at a point where there isn't any unusual behaviour from the motor, nothing strange has been in the oil, and there are no strange noises - I'm gonna leave the cam bearings alone for now. Cheers.

Yea, like I said just go up onr grade of oil and leave it.
But the cam bearings will be like 3.5 to 4 thou when you tear it down.
Not too far out but when you account for pressure drop across the crank it's fairly large.

 

[WreckWren]

Yea, like I said just go up onr grade of oil and leave it.
But the cam bearings will be like 3.5 to 4 thou when you tear it down.
Not too far out but when you account for pressure drop across the crank it's fairly large.

Yeah that's it mate. Without doing the cam bearings as a precaution, best option is to go up in the main (not winter) weight of oil.

 

[ZXTC]

Mine was the little black o ring on the oil pump causing low pressure at 310,000 kms. I run Castrol 10w 60 atm.