Losing Oil Pressure?

[OBS_Build]

Ok so since I first changed the oil on my 96 k1500 with the 5.7 my idling pressure has been at 40 pounds. When I got on the truck it was 60 pounds and that didn't change with the temperature of the engine. But now, I put 10W-40 full synthetic high mileage oil in it just like every other time, before the truck warms up the pressures are at 40 idling and 60 when I'm on the gas, however when the engine warms up, the pressure drops to 20 and idle and 40 when I hit the gas. Does anyone know what could be solving this or if its something I need to be worried about. The only check engine codes are for the catalytic converter and the EGR.

 

[df2x4]

20psi at hot idle and 40psi moving sounds fine for a 5.7L to me. I would be curious what your pressure is with 5W-30 though, that's what the manual calls for.

Personally I'd be more worried about the EGR and the catalytic converter if I were you.

 

[PlayingWithTBI]

^^^What he said. I use Mobil1 10w-40 because, IMO the heat in AZ, I have about the same pressures.

 

[Schurkey]

For the record, and not that anyone cares:
GM quit recommending 10W-40 motor oil before I was working in the dealership in '84, because "no 10W40" was already policy when I started there. I suspect that was when many companies began to produce 15W-40.

 

[evilunclegrimace]

For the record, and not that anyone cares:
GM quit recommending 10W-40 motor oil before I was working in the dealership in '84, because "no 10W40" was already policy when I started there. I suspect that was when many companies began to produce 15W-40.

They have since changed their minds, 5w-30 is the norm in a lot of newer vehicles

 

[Schurkey]

They have since changed their minds, 5w-30 is the norm in a lot of newer vehicles

No, the dealership was pushing 5W-30 way back then. Folks who wanted thicker oil got straight 30. But I think 15W-40 came about because of GM ******' and moanin' about 10W-40.

I never saw a GM bulletin on the subject, but "the story" was that 10W-40 "had too much viscosity-index improver" in it, and that led to engine deposits that "clogged the rings".

I'm sure there IS a bulletin--or five. I've just never seen it/them.





Just like automatic trans fluid, engine oil gets thinner and thinner. 0W20 is popular now. We don't care about bearing protection, we care about parasitic losses and how they affect CAFE regulations (fuel economy.)

 

[454cid]

Ok so since I first changed the oil on my 96 k1500 with the 5.7 my idling pressure has been at 40 pounds. When I got on the truck it was 60 pounds and that didn't change with the temperature of the engine.

That would be highly unusual for the oil pressure to be that high and not change with the temperature.

I'd recommend you use 10w30, or 5w30.

 

[OBS_Build]

That would be highly unusual for the oil pressure to be that high and not change with the temperature.

I'd recommend you use 10w30, or 5w30.

Ok thanks

 

[Supercharged111]

For the record, and not that anyone cares:
GM quit recommending 10W-40 motor oil before I was working in the dealership in '84, because "no 10W40" was already policy when I started there. I suspect that was when many companies began to produce 15W-40.

I think the manual for my 98 recommends 10W40 as one of the summer options?

 

[98chevy2500SS]

Those oil pressures sound fine for the Vortec 5.7. Tbh, these oil pressure gauges aren't the best, they're good enough, but an aftermarket oil pressure gauge will give a better read out of the pressure.