Oil pressure issue

rdezs said:

... More frequent oil and filter changes slow down that process tremendously.
I understand the GM oil life monitor is actually highly rated, and was done with several years of study with oil analysis.
I'm just not sure, and I have my doubts, if their studies were actual real world conditions. I feel the safe bet is to change it every 3,500 to 5,000 miles.
(The oil life monitor can vary all the way up to and beyond 8,000 miles.)

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Your doubts are neither entirely right, nor entirely wrong.
In principle, GM's Oil Life Monitor tracks and accounts for lots of things that odo mileage just can't:
*How often the engine is shut down and restarted, engine temp at restart
(likely ignored by vehicles with 'snooze feature', quite possibly to that engine's detriment)
*How much more time the engine spends at operating temp vs 'warming up'
*How conservatively or aggressively it's driven, vs how much time it spends with the TCC locked
(obviously worst to drive aggressively while warming up only to shut down before fully warmed up)
*How much time the engine spends idling (odometer alone cannot account for this at all)

The Oil Life Monitor is basically a 'bank' of engine RpMs.
The more slowly RpMs are accrued, the better, obviously.
The above list and several other factors 'penalize' those 'RpMs' more quickly than one might expect.

If the engine suffers an overheat, even briefly, the OLM drops to 0.
However, GM defines an overheat as 257F (if not hotter), whereas I define it as 239F.
(By the way, EVERY UNDERHOOD FLUID should be changed ASAP after an overheat, including brake fluid, is how paranoid I am.)

If it spends most of its service life getting 20MpG (or better), it needs oil changes
less often than an otherwise identical vehicle that gets 10MpG.

The OLM tries to account for whatever nuances are left after MpGs.
However, it is entirely possible to account for every mechanical factor,
and STILL be influenced by the environmental lobby.

More to come ...

GM recommends oil changes when it hits 15%, but never over 1 year regardless of miles.
Your skepticism is shared by NYC cabdrivers, by the way.
FYI, most NYC cabdrivers / livery drivers / chauffeurs apply the following 'skew' to the Oil Life Monitor:
Mostly all highway miles (NOT NYC), change oil & filter @ 17%, NEVER over 5000 miles.
More highway than local miles, change oil & filter @ 20%, NEVER over 4000 miles.
More local than highway miles, change oil & filter @ 25%, NEVER over 3500 miles.
Mostly all local miles (stop'n'go, LOTS of idling, also lots of restarts), change oil & filter @ 33% -
NEVER over 3000 miles.
If they intend to keep that car after the lease is up,
some oil changes may occur as often as every 2500 miles / every 5-6 weeks,
depending on the nature and number of miles accrued.
The ones that intend to keep it after the lease is up also disable Engine StopStart and Cylinder Deactivation.
By and large, they are NOT keeping the ones that do not allow disablement of DFM.

Again, a simpler way to account for all of the above:
the better the lifetime average MpGs, the less often the oil changes.
the worse the lifetime average MpGs, the more often the oil changes.

@swathdiver After the AFM delete, oil pump, and o-ring it didn't change the oil pressure but I did end up using a standard oil pump instead of the high flow or high volume options so it's possible that a different pump would have given better results but I am satisfied with the numbers I have

Look up the various GM models under the brand name Holden in Australia.

Just wrapped up the neighbors AFM delete. Plugged the towers, and plug the pressure relief valve in the oil pan. We installed a Melling 10296 with the +10 PSI spring that comes pre-installed. LS7 lifters, measured for push rods and the 7.4's came out at .085 preload.
L92 OEM camshaft. All new stuff under the front cover. 34 PSI@hot idle. 1500 RPM is 56 PSI. Did the crank relearn, which requires running it up to 4,000 RPM. Peaked out at 72 psi. We did a lot of stuff while we were in there, new water pump of course and new radiator. Cut out the section of OEM hose in the transmission cooler lines. Use compression fittings to go to AN6, and converted the transmission cooler at the radiator to AN6 fitting. Purrs like a kitten. We also replaced all the O2 sensors with genuine GM, as well as the oil pressure sending unit, Cam and crank sensors.

And this is what we found for the front cam bearing. Sent the scope through the rest of them and they looked like new. Was really surprised to see how well the front bearing looked.

rdezs said:

And this is what we found for the front cam bearing. Sent the scope through the rest of them and they looked like new. Was really surprised to see how well the front bearing looked.
View attachment 454299

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That looks better than zero mile crate engines but I've seen pics of



There's a theory out there that says they align hone after installing the bearings at the factory due to cheap casting shift. others say it's just the lowest possible quality cam bearing anyone has ever seen to save a buck

I've heard from multiple sources that the factory align homes the bearings after install..... But not 100% sure that I buy that. If the bores were that far off, and replace the cam bearings, you'd never get the cam in. And it seems like if it did, you wouldn't be able to turn it. Anybody object to that theory? LOL