Oil pressure concern

[weo38]

When should I be concerned my oil pressure is getting too low? At idle I get about 25psi and at 70mph I get 40 psi. I am running 10W-40 Synthetic oil. I am just getting a little concerned I may be into a rebuild/replacement in the near future. Truck has 102,000 miles on original motor.

[maxwedge]

What are you comparing this to, what did it used to be, also you may want to hook up a mechanical gage at the oil sending port and verify the dash readings.

[weo38]

I guess i am comparing it to what i was seeing before. I would have like 40-45psi idle cold and 45-55at highway speeds. Not sure why it would drop off that much. I am a little skeptical of the gauge as well.

[j cAT]

Originally Posted by weo38

When should I be concerned my oil pressure is getting too low? At idle I get about 25psi and at 70mph I get 40 psi. I am running 10W-40 Synthetic oil. I am just getting a little concerned I may be into a rebuild/replacement in the near future. Truck has 102,000 miles on original motor.

your not to use 10-40wt oil. this oil was banned by GM back in the early 1980's.

your engine should be 5-30wt or 10-30wt. synthetic is best.

why not 10 -40 ????????? because it wears out the engine.


I use 5-30wt synthetic well over 100,ooomi I use 1/3qt at my 8,ooomi oil change . 2000 5.3L silverado original owner..

stay away from FRAM OIL FILTERS !!!!

[weo38]

So you are basically saying I am screwed because I used 10w-40? If I change back to 5W-30 my oil pressure will be less right? I went to the 10w-40 because it was said to be used in high mileage vehicles.

[j cAT]

Originally Posted by weo38

So you are basically saying I am screwed because I used 10w-40? If I change back to 5W-30 my oil pressure will be less right? I went to the 10w-40 because it was said to be used in high mileage vehicles.

you could be screwed . check the pressure with a mechanical guage .

40-50 psi when warm is what I get. when at very cold start I get 65-70psi.


use wix,purolator Plus,napa gold oil filters and 10-30wt oil. see what you get for pressure. 25psi at idle is fine/// below 20psi is getting low.

25 psi however is not the normal idle oil pressure.

If you used synthetic from the day this vehicle was built , the engine would have very little wear. hi mileage oil formula is for worn, abused engines that used non synthetic oils, poorly constructed oil filters and going too long on replacing the oil.

the engines in these vehicles go about 200,ooomi . when properly maintained..

[maxwedge]

One time use of 10-40 will not be an issue, the 10-40 back in the day tended to " coke" up because of higher engine and combustion temps. As j cAT said it is not designed for modern engines.

[j cAT]

Originally Posted by maxwedge

One time use of 10-40 will not be an issue, the 10-40 back in the day tended to " coke" up because of higher engine and combustion temps. As j cAT said it is not designed for modern engines.

like you said and I agree the mechanical guage test is needed.

looks like his pressures are off hot / cold by the same amount. the sender is very possibly out of cal..

[weo38]

Happy to report that after a check with mechanical gauge and then an oil change back to 5w-30 the oil pressure is reading higher and more in the range before I changed to 10w-40. The mechanical gauge and the gauge in the truck read about the same at idle cold with 10w-40 (40 psi). After changing the oil and filter the gauge now reads 40 at idle and between 50 and 60 at highway speeds(between 60 and 70 mph). I feel better now and hope to keep these readings as the oil gets used.

[jdmccright]

Sounds about right. Remember the second number is the relative viscosity at operating temperature. So, the -40 oil will be more viscous and thus harder for the oil pump to move than the -30 oil. The -30 oil flows better, i.e. less resistance to flow, allowing the oil pump do less work to move the oil.