Motor Oil Brand vs Pressure?

I have been cycling through various brands of motor oil at changes and noticing differences in our 5.3 Tahoe usage.

I've always use the same weight all synthetic oils with the same AC Delco filters and just varied the oil brands.

In the latest brand trial I have noticed a 5 psi drop in idling hot oil pressure (40 down to 35) but a 5 psi increase at 2000 rpm (also hot) from about 50 to 55.
Does it make any sense that a particular oil brand would cause an oil pressure variation?

With the brand immediately before this one I noticed a persist burned oil odor but there are no leaks or stains to be found. The odor is gone with the current brand.

The brand before that seemed to lose (burn off?) more than a quart between oil changes, perhaps at 5000 mile intervals or so.

I don't know if it's the oil but it is odd.

Does this make any sense?

What brands produced the results you list?

I can't imagine why it would be the oil brand. They are supposed to produce the oil to a specified viscosity.

Are you using the same oil filter?

But even if there is a 5 psi +/- difference, why would it matter? I wouldn't be concerned myself.

strutaeng said:

I can't imagine why it would be the oil brand. They are supposed to produce the oil to a specified viscosity.

Are you using the same oil filter?

But even if there is a 5 psi +/- difference, why would it matter? I wouldn't be concerned myself.

Click to expand...

Same filter brand and model, but that's not to say something inside is not different.
It raises an eyebrow because for 16 years it has always been consistent at 40/60.

OR VietVet said:

What brands produced the results you list?

Click to expand...

Castrol Edge High Mileage is where pressure variations are noticed. Also startup is noisy (tick, tick) for a few minutes. Too soon for usage.
Quaker State Ultimate Protection was where burned oil smell was consistently noticed but startup is quiet. That ended with another oil.
Shell Gas Truck seemed to use some but less than Pennzoil, was quiet but about 2x cost because it's apparently discontinued.
Pennzoil Platinum High Mileage is where I seemed to use the most oil and I seem to recall start up noise, tick, tick for a few minutes.

All were specified 10W30 full synthetic. Not all are Dexos rated.

This is not written to disparage any products but only to show how my truck appeared to respond to them.

Any of it make any sense?

Edit for oil weight: 5W30 is what is used. (Too many vehicles to recall on the spot)

We, all the car guys in my Navy squadron, avoided Pennzoil 50 years ago. It was burned quicker and left tailpipes sooty.

joe

I also try different on sale oil's and I also notice some make the engine sound different from others.
I do not keep track of brands and i have no empirical evidence to show proof of anything, just my own personal observations.
Some create more piston slap and tic on start up than others and I end up changing them out within 500 miles and go back to the same two brands with Wix filters.
Mobile 1
Royal Purple
Both full synthetic 5W30 as called for and the engine sounds happier
I would be interested in what adding some ZDDP does but, that is bad for cat's so not willing to risk needing new ones for an experiment.
I want to also try Amsoil and see how that stuff is.

I stick with WIX and either 5W-30 Mobil 1 or Valvoline full synthetic. No problems.

the weight of oil is a range. the thickness can very and still fall within spec to be called say 5 or 10. the ls oil pump is gear to gear, which in theory breaks down oil faster than a vain style, like the LT probably just theory thou. so it's not a stretch to say if you sent 2 different brand samples off for testing and they gave you a weight. which they don't but it could be measured. that one could be thinner than another after 5k miles of use.

a rule of thumb that I hear that made sense to me was if the engine is quieter, there's probably less wear going on. if you find a brand that doesn't tick, I'd personally stick with it.


my personal suv is pretty quiet, so I haven't noticed much difference in sound. I have ran a lot of mobil 1, and then I ended up with some free Pennzoil Ultra Platinum, so I ran that for 2 chances. couldn't tell any difference to be honest and I only put about 3500miles on oil. I thought about sending a sample out, but said eh and just happened to change it earlier today.

the internet hype got me and I picked up this restore and protect stuff. see how it goes. so far no extra noise.

psi I have no idea. it's always high

EddieC said:

I have been cycling through various brands of motor oil at changes and noticing differences in our 5.3 Tahoe usage.

I've always use the same weight all synthetic oils with the same AC Delco filters and just varied the oil brands.

In the latest brand trial I have noticed a 5 psi drop in idling hot oil pressure (40 down to 35) but a 5 psi increase at 2000 rpm (also hot) from about 50 to 55.
Does it make any sense that a particular oil brand would cause an oil pressure variation?

With the brand immediately before this one I noticed a persist burned oil odor but there are no leaks or stains to be found. The odor is gone with the current brand.

The brand before that seemed to lose (burn off?) more than a quart between oil changes, perhaps at 5000 mile intervals or so.

I don't know if it's the oil but it is odd.

Does this make any sense?

Click to expand...

Perfect sense! Regular Mobil One burned in my motors, needing 1-2 quarts of make up oil between changes. We also noticed lower pressure but my memory seems to recall it was more due to the filter used and not the oil, could be wrong though.

The ACDelco oil and Quaker State oils I'm using now have been fantastic. No make up oil, no rattling on start up and good pressure.

I've also had the oils analyzed and the ACD and QS oils blow M1 out of the water by keeping metals out of the oil. It just ain't what it once was.