Elevated Oil Pressure on Changing to Castrol Edge

**bertwhitaker** · 09-01-2009, 06:23 AM

So I changed the oil in the 1998 Trans Am to Castrol Edge recently (from Mobil 1, full synthetic). The oils are both 5W-30, but, with Edge, it seems the oil pressure is running higher than it did with Mobil 1 by about 10 PSI. On startup, M1 had maybe 45-50PSI, but Edge gives perhaps 55PSI. After things warm up, at idel, Mobil 1 gave maybe 30-35PSI, but Edge gives 40-43PSI. At perhaps 4500-5000rpm, Mobil 1 I think gave 45-48PSI, whereas Edge is giving 60-62PSI.

Why would this be occurring if the two oils are of the same weight (5W-30)? What’s going on altogether? I am totally freaked out about maintaining excessive oil pressures, as I think that makes it more likely that my rear main seal (or similar seals) may fail. Am I correct to worry about the high oil pressures causing the rear main and other seals to fail prematurely?

**bertwhitaker** · 09-01-2009, 06:27 AM

Should I just ride it out with this oil in the car until my next change (2000 miles), or should I immediately drain it out and put back in some Mobil 1?

**astyles** · 09-01-2009, 07:57 AM

pm Sarge and see what he says.....

**ss~zoso~ss** · 09-01-2009, 07:26 PM

if they're the same viscosity, in theory they should yield the same pressure.

now, do you happen to remember the conditions under which you changed your oil the past 2 times. you may have had more oil left in your engine this last time, yielding higher oil pressure

**bertwhitaker** · 09-02-2009, 06:59 AM

It is my understanding that, as long as the oil volume is above a certain level, the pressure is unaffected. What I mean is that, as long as the pump is getting oil, and there's enough to get to the end of the channels, the pressure is the same, even if there's an additional quart or two of oil. Having said that, my car (knock on wood) does not leak or use any oil at this point, nor has it in the past. My impressions of the pressure change is based on my year-round experience with Mobil 1.

**blackSS01** · 09-06-2009, 07:31 PM

I'm pushing 75 psi at idle warm. No leaks yet

**CompSyn** · 09-07-2009, 02:01 PM

Originally Posted by bertwhitaker

So I changed the oil in the 1998 Trans Am to Castrol Edge recently (from Mobil 1, full synthetic). The oils are both 5W-30, but, with Edge, it seems the oil pressure is running higher than it did with Mobil 1 by about 10 PSI. On startup, M1 had maybe 45-50PSI, but Edge gives perhaps 55PSI. After things warm up, at idel, Mobil 1 gave maybe 30-35PSI, but Edge gives 40-43PSI. At perhaps 4500-5000rpm, Mobil 1 I think gave 45-48PSI, whereas Edge is giving 60-62PSI.

Why would this be occurring if the two oils are of the same weight (5W-30)? What’s going on altogether? I am totally freaked out about maintaining excessive oil pressures, as I think that makes it more likely that my rear main seal (or similar seals) may fail. Am I correct to worry about the high oil pressures causing the rear main and other seals to fail prematurely?

There is a range for 30-grade motor oils to meet SAE specs. For example, in order for a 30-grade to be labeled as a 30-grade, it has to have a viscosity somewhere between 9.30-and-12.49 @ 212 (F).

If you look at the Product Data Sheets of both Mobil 1 5W-30 and Castrol Edge 5W-30, the following it listed:

Mobil 1 5W-30 11.3 @ 212 (F)

Castrol Edge 5W-30 9.8 @ 212 (F)

So going be the Product Data Sheets, the Castrol Edge is thinner by a little when compared to Mobil 1.