OIL PSI / BRAND / WEIGHT

Hi everyone,

I know oil pressure seems like a common question. But, what I don't understand is the constant variations; especially when there is void of any precursor. I have a 2003 4x4 with a 5.3. I replaced the pump, timing equipment, and pick up tube, gaskets ect. And it ran 35-40 PSI cold or hot idle, and around 45-55 under load. This truck had around 224k.

I have another 2001 2 wheel drive, and when I got it, it idled around 30 PSI cold, and 25-30 hot, and under load 39 PSI. I have been delivering for a company packages 3x a week for several weeks, the truck has been running 8-12 hour days, 80 miles a day and idling with limited start and stops. The oil, when cooled and dropped to the pan is a bit tacky, but not dirty. I maybe burned off at most half a quart since I changed the oil about 1500-1800 miles ago. Just last night my oil PSI seemed to be warm fighting 20-25 PSI sometimes not going past 20-22 PSI, and under load various pressures between 32-39 PSI approximately. Noticing a drop here.

I am getting ready to change the oil, and I did some research and shows that Royal Purple HPS has the most zinc at 1275, most oils are more more than 950. Apparently RP is not API standard, so they can add whatever they want, and their film strength is also superior, as I have seen in several test videos. Im looking for a bit more zinc and some extra film strength to keep it going longer. I was hoping to increase some pressure by having a thicker oil. I was thinking of adding some lucas to my current oil brand. But then I seen the natural lucas thickness, and I said what if I just use that and increased to 5w40 instead of 5w30? I heard a lot of people allege lucas made their bearing tolerances worse, so it improved temporarily, but just made the inevitable happen with just straight weight oil. I ahve been using Valvoline MAXlife high mileage for over a decade, but I feel in this engine maybe its not appropriate.

My plan was to use RP 5w40 and a good quality filter, possible replace the oil sending unit. And then say in 1,000 miles run some marvel mystery through it for another 500 miles, and then do a complete straight RP 5w40 swap until I have to change the pump out. Sound like a good idea?

Have you watched Lake Speed Jr's videos on oil additives on YT? He's got a lot of excellent videos out there.

I don't remember all of the names and stuff of what's what... because I've since slept, LoL. But I just remember that regular oil changes with quality oil is better than adding additives, which can actually cause bad effects due to the chemistry mixing up. I believe high zinc is only for initial break-in of engine parts like piston rings and such. Too much of it can actually cause catalytic converters to die faster. That's why they reduced the zinc in the oil. Auto manufacturers wanted cats to live something like 200k. I think that's what I read.

I wouldn't worry too much about what your needle is saying, unless it's zero. The cluster isn't even calibrated to "psi", I don't know if you knew this or not...I literally had just mentioned this on another forum. If you really want to know what the pressure is, hook up a mechanical guage.

Just do oil changes based on "severe use," whatever that is.

Why not do a used oil analysis, see what they have to say?
We all got fixated on oil pressure, which is almost too easy to measure, then somehow decided 'more is better'.
Reminds me of wanting and getting more boost, then wondering why the engine isn't making more power.
(Then when he finally learns enough to make more power, he wonders why it doesn't translate to a quicker 1/4mile ...)

More difficult to measure but more important is whether or not oil is getting where it belongs, and moving smoothly through it all.
Once it does that, it carries away contaminants and other stuff, suspending much of it, some of it getting trapped in the filter.

Think you're better off getting a used oil analysis.

Thank you for the ideas.
I was not aware of the lack of calibration. Although it is not expressly printed on the dash, I assumed GM would have made something close to calibration at least.

I spoke to Royal Purple, Valvoline, and Lucas today. I hate to say this, but I feel Lucas may be pointless. One company said testing showed extra wear on the engine, and the Lucas product essentially warmed up and most if not all of the added viscosity almost quickly disapeared. I used it 10 years ago, and I really don't remember it. Valvoline confirmed the Maxlife BLEND that I have been using has the Zinc ad 790 PPM and the full synthetic at 820PM. Compared to the 800 in royal purple standard synthetic.

Accoding to the PQIA-
Royal purple ZINC is 800PPM, Phosphorus at 690PPM and Boron at 211
Valvoline Max Life Blend ZINC 887PPM, Phosphorus at 765PPM and Boron at 186

I have seen videos where Royal Purple is just superior on film strength though, how and why?
can our 5.3s take a 5w40? how much PSI wold increase by a thicker oil ?

I ordered an oil test kit a while back waiting for this moment.

YukonLover said:

Thank you for the ideas.
I was not aware of the lack of calibration. Although it is not expressly printed on the dash, I assumed GM would have made something close to calibration at least.

I spoke to Royal Purple, Valvoline, and Lucas today. I hate to say this, but I feel Lucas may be pointless. One company said testing showed extra wear on the engine, and the Lucas product essentially warmed up and most if not all of the added viscosity almost quickly disapeared. I used it 10 years ago, and I really don't remember it. Valvoline confirmed the Maxlife BLEND that I have been using has the Zinc ad 790 PPM and the full synthetic at 820PM. Compared to the 800 in royal purple standard synthetic.

Accoding to the PQIA-
Royal purple ZINC is 800PPM, Phosphorus at 690PPM and Boron at 211
Valvoline Max Life Blend ZINC 887PPM, Phosphorus at 765PPM and Boron at 186

I have seen videos where Royal Purple is just superior on film strength though, how and why?
can our 5.3s take a 5w40? how much PSI wold increase by a thicker oil ?

I ordered an oil test kit a while back waiting for this moment.

Click to expand...

Post #5....is what I was saying...

I will try to find the Lake Speed Jr's videos I was talking about later today...I think it will surprise you if you haven't seen it about "oil additives"...

Did the 2001 XL have an oil cooler? I know my 2003 does

Engine oil cooler was more like a towing RPO code option. Not related to year or another...

You can always just add one too.

Here's a link to the video and discussion on tbe topic: https://www.tahoeyukonforum.com/threads/lake-speed-jr-oil-additives-snake-oil-video.148337/

YukonLover said:

Thank you for the ideas.
I was not aware of the lack of calibration.
Although it is not expressly printed on the dash, I assumed GM would have made something close to calibration at least.

Click to expand...

Even if that assumption were true, my '02 Tahoe now idles at operating temp @ 360RpM ...
... at least according to my tachometer's needle, which has clearly escaped its original tolerances.

Can't wait until a fully digital / non-mechanical dashboard replacement becomes a thing ...

strutaeng said:

I wouldn't worry too much about what your needle is saying, unless it's zero. The cluster isn't even calibrated to "psi",

Click to expand...

Wait a minute.. So then what is it calibrated to? Even if the dummy gauge as i call them are not entirely accurate.. which i never truly believe they are, it’s still got to be reading in psi…. Even if it is not a precise reading..

Right ?