Using oil pressure to determine viscosity?

[427Z06]

Quote:

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cfromc, GM has gone on record as not wanting any 20Wt. oil used in any of their vechiles not specificly recomending it. To date only those GM vechiles with Honda V6's are calling for a 20Wt. oil!! We only have a few UOA of GM vechiles on 20Wt. oils. If you are trying to save money with thin oil I would instead look for a more fuel effecient vechile!A synthetic 0W30 or 5W30 are about as thin as I would go. Last I checked GM alloyed 0W30's to be used in all of their engines.

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Huh? So all those posts where you rail against manufacturer's recommendations since "they couldn't possibly know how you're using the vehicle" and "manufacturers screw up all the time so one needs to make an informed choice" doesn't apply anymore?

 

[cfromc]

Oh, this new system of checking each post before it gets entered is killing me. I've already done two and came back later and they weren't there. Anyway, to answer your questions: I tried Amsoil series 2000 0W-30 and the engine made more noise than it ever did before. I actually never heard any piston slap before that. I don't believe the oil caused it, it was likely just that engine's time. I used the XL-7500 5W-30 and the noise was shorter and quieter. Now I'm on my second fill of the XL and I added some MMO to it and the noise has again gotten shorter and quieter. I plan on doing a top-engine clean just before my next oil change and then going to Redline. I may consider running half XL 5W-20 and half XL 5W-30 and doing 7500 mile OCI. I wonder if I can run an Amsoil EaO filter and just change the filter after every second OCI if running the XL oil? Otherwise I plan on doing 10K+ OCI with RL and change the filter each time.

 

[jorton]

Base viscosity choice on oil temp if you can install a digital gage.

How long should it take to reach 100c? I suppose it takes longer on the highway so it also depends on driving style and conditions. Joe

 

[1sttruck]

Something else that would help to dial in a different oil, or address some related questions, would be an 'orthogonal oil pressure gage', consisting of a regular oil pressure gage, with the sensor normal to the flow, and another sensor mounted facing the flow. The gage, with two readouts, would indicate the oil pressure that we're familar with, and also would indicate flow. I've not heard of such a thing being used, but all the pieces parts are available.

 

[Blue99]

Just my observstions on the effects of 2 viscosities on oil pressure in my GM 5.3L.

Readings are from the OEM dashboard gage, at 1650 rpm and 60 mph with the engine at full operating temperature (after a 9 mile freeway run at 70 mph).

Havoline 5W-30, 10.5 cSt..........53 psi

Chevron 10W-30 & 15W-40
2/3 to 1/3 mix, 12.5 cSt..........53 psi

So, at a constant rpm, viscosities in the 10-12 cSt range would appear to generate very similar oil flow & pressure levels.

 

[lt2000]

Changed to 5W20 in the 5.3 silverado and the oil pressure is 45psi @500 rpm idle,up to 55psi at 1650rpm the temp here in north texas today was mid 90's
Gary