Lower oil pressure with miles on oil....

[Sink]

My oil pressure has been reading noticeably lower lately, with about 2500 miles on my Syntec 10w40. I assume this is because of shearing? I'm running this weight of oil because it provides more comforting oil pressure in the first place. This is on an engine with 255,000 miles... Is Syntec especially bad about shearing?

I was told when I bought the truck that it's had nothing but Syntec its whole life, so I've used it too. I have changed all the other fluids with Valvoline ones, and I'd like to run SynPower. Is there a reason not to switch?

 

[OVERKILL]

No reason at all. Switch away.

 

[oilboy123]

Does it use any oil? Go for the Synpower......

 

[demarpaint]

No reason not to switch, but if its oil pressure you're looking for a dino will give more pressure, the brand change could help with a different synthetic oil. Synthetic flows better showing a lower pressure reading, but its oil flow that lubes and protects an engine.

If you are really concerned and don't already have one, get a mechanical OP gauge and get actual readings, that will tell it all. It is a high mile engine and that will take any guessing out of the equation.

 

[Jaymus]

If Syntec got it to 240,000 miles, and it still is running good, I wouldn't change anything. Question is, what psi are you getting at idle and running speeds? And what engine are we dealing with, here?

 

[TallPaul]

Your assumption makes perfect sense to me. Oil shears, pressure is lower. I have never experiences such a drop in my F150 which I ran 10w40 for several years, both Maxlife and Durablend. Try a different brand and see what happens. Or go with a 15w40.

 

[Sink]

Originally Posted By: Jaymus
If Syntec got it to 240,000 miles, and it still is running good, I wouldn't change anything. Question is, what psi are you getting at idle and running speeds? And what engine are we dealing with, here?


When the oil is fully warmed up, like at the end of my 30-40 minute commute... Idle: ~15psi / 70mph (2100rpms):~38psi

This is on a 4.3L Chevrolet Silverado. These numbers were slightly higher on fresh oil.

Would it be harmful to the motor to switch to an oil that wasn't fully synthetic? I'd like to use Valvoline HM 10w40 because they don't offer a Synpower 10w40.

 

[demarpaint]

The numbers ~15 psi at idle, engine fully warmed up, and then ~38 psi at 2100 rpms are fine.

As far as switching to the Valvoline HM oil, it would also be fine. However the Synpower will give better flow at a cold start up, but in Louisiana I don't think that will matter much.

I also agree with Jaymus if you driven 240,000 miles on Syntec it treated you well.

JMO

 

[Sink]

I agree with him also, it can't be too bad if it has gotten the truck this far. And I'm not saying my oil pressure numbers are bad, considering my use of synthetic oil and how many miles are on the engine. I'm just a Valvoline guy but I guess I can get over that in this case. I did put Valvoline in the rear end and tranny though.

 

[glenncof]

At 255K I would be more concerned about consumption and lean toward heaver overall weight in your climate if it's using.

I've run 20W50 all year in Northern California and my engine only has 197K.

SynPower 20W50 is nice stuff.
PP 15W50 is too.

 

[Sink]

glenncof, I would be concerned too if it used any oil. But I checked my oil today and with 2500 miles on this oil and no top-off oil added, I'm still full. My concerns are protection so this motor will last a lot longer, and cleaning properties to maintain what I assume is an already clean engine.

 

[tig1]

Try M1 10-40HM. Strong oil for high mileage engines,BTW what kind of truck do you have?

 

[demarpaint]

Originally Posted By: Sink
glenncof, I would be concerned too if it used any oil. But I checked my oil today and with 2500 miles on this oil and no top-off oil added, I'm still full. My concerns are protection so this motor will last a lot longer, and cleaning properties to maintain what I assume is an already clean engine.


2500 miles the oil is still full, the pressure #'s looked pretty good too. I think you're trying to fix something that isn't broken. I'd say you did a good job maintaining the vehicle, and the oil has done well too. If you start using oil, then perhaps changing the viscosity of the oil might be in order. For now I'd leave well enough alone.

My opinion...........

 

[Sink]

tig1, it's a 94 Silverado.

Originally Posted By: demarpaint
Originally Posted By: Sink
glenncof, I would be concerned too if it used any oil. But I checked my oil today and with 2500 miles on this oil and no top-off oil added, I'm still full. My concerns are protection so this motor will last a lot longer, and cleaning properties to maintain what I assume is an already clean engine.


2500 miles the oil is still full, the pressure #'s looked pretty good too. I think you're trying to fix something that isn't broken. I'd say you did a good job maintaining the vehicle, and the oil has done well too. If you start using oil, then perhaps changing the viscosity of the oil might be in order. For now I'd leave well enough alone.

My opinion...........


Actually I'm not trying to fix anything. I am concerned because the oil pressure, while it is still good, was noticeably higher on the gauge at the beginning of this interval. So my concern is not my truck, it is the particular oil I have chosen, and my question was whether this was normal shearing for all oils or if Syntec is especially bad about shearing.

The only thing I'm considering changing is the brand of oil I use, and that is because of loyalty --- not because this oil is performing poorly.

 

[BuickGN]

It's possible. The pressure on my GN falls slightly as the interval is near it's end.