I never really knew there would be much difference between 5 and 10w-30...

Just to be clear, the psi was dropping to zero even before I changed it with 5-30...

I may have just been paranoid with the white smoke rolling out... ITs very humid and chilly today- doesnt smell like burnt oil or sweet antifreeze

 

There isn't any difference really. 5W-30 and 10W-30 have to meet the same API viscosity spec at room temperature and at 100C/212F. The W viscosity only matters below 32F. If it's colder than room temp outside, 5W-xx *might* leak a bit more, if you have leaks. But both oils (assuming they're conventional oils) will be made from the same base stock if from the same manufacturer and quality; probably somewhere between 20 and 30 wt (there are no 10 wt conventional base stocks). The additive package is responsible for the lower W rating, which will be different.

5 minutes or less of driving and they are the same. The oil is not the source of your oil pressure problem. If the sender (or another known good sender) is giving you accurate readings, I would suspect oil pump next.

I believe these engines use a Georotor pump; that style of pump is very sensitive to clearances [gear to gear and gear(s) to pump body]. Could be some debris got in there or it's just wearing. It's worth keeping in mind that the oil pump is lubricated by un-filtered oil picked up from the sump; the filter for whatever oil is circulating through the engine galleys is after the pump. So although oil pumps are generally reliable, the screen protecting the pump is more than large enough to pass maybe an 0.040" or 0.025" chunk of debris; the pump clearances are much smaller than that, so worn pumps are hardly unheard of. The damage can be caused by relatively soft materials, not necessarily metal.

You could check main bearing clearances with the pan off. That will kill pressure if excessive, and probably points to a reconditioning of the engine. But you could also check clearances in the pump when you remove it. If it's worn, you could just skip the bearing check and see. You should replace the oil pan gasket.

 

Never mind then

 

My truck started doing the same thing last week. Right after I changed the oil for the first time since I have owned the truck. I have only owned it for about a month now and I switched the oil to Royal Purple 10w30. My dash light "check gauges" would come on the the oil pressure on the truck would read 0. I changed my plenum today and the problem hasn't come back....yet anyways. My oil pressure is slightly higher with the new plenum too.

 

On a high mileage motor, go for the high volume pump. Granted, it's a bandaid fix, but, it will let you get some more life out of your motor.

Grab the service manual from the faq section here, we have a selection. Get the one closest to your style of truck.

While you have the oil pump out, change the rear main seal as well.

It's really not a bad job. Took me a couple hours the first time..... bit less the second.

 

you know in theory what your saying makes perfect sense but my experience with experimenting with different oils in my vw tells me otherwise.... along with many many threads there debating the issues and side effects with different weight oils... they did make a difference both in oil pressure and in temp.as well as the amount of blowby .. maybe not so much 5w vs 10w but I know some thicker oils do run differently even when at full temp.

 

Thanks for the replies guys!

I just finished cussing after my test drive... 60 psi until it warms up then around 20 psi and eventually hits zero every time engine rpms get low
I bought the original pump figuring I wasnt adding any mods and that it would work fine, after reading some I probably should have splurged the extra $30 ha ha

So mechanical gauge still drops to zero after new oil pump, 10w-30 oil, and I added some "engine restore"... Seems like it cant hurt

Rear main was shot too but I didnt have a gasket on hand......

I also didnt measure any clearances while I had the pan dropped, I wish I would have read that before I started


So where in the heck do I go now?

 

Back into the pan unfortunately. Check bearing clearances, and see what they look like. If they are out of spec, you may be able to simply replace them, and be done with it. (at least its a job you can do lying down.....)

 

 

Is that the only possibility left if I can ask?