I purchased a 1999 GMC Cutaway Van with a 6.5td, it has 207,000 miles on it. I belive the first 107,000 miles were operated by Penski as a lease vehicle, and the rest by a private deilivery party. Now, as I purchased the vehicle for $3000.00, I figured I was looking at putting money into it. The first thing I noticed was it had a vehicle engine alarm on the dash "Put in by penski I would imagine" after the vehicle warmed up the low oil pressure gauge would show 15-18 at idle, and the engine alarm would sound. So I replaced the existing oil sender unit with a manual O.P.G. and found it was really more like 3-5 psi at idle. -:t I recently contacted a dealer and found 6 psi was actually the norm. on that. So my FIRST QUESTION what is the oil pressure supposed to be at during idle, and at say 55MPG as I dont have a RPM guage. Then my SECOND QUESTION is the engine alarm STILL new the pressure was low after the engine warmed up even though the pressure sender was unplugged with the manual gauge installed. But beyond all that I just what to know what order I should take to increase the O.P. if any.

1: Should I do a sludge oil sludge removal- and what method?
2: Change oil and get a thiner oil I.E. 30 S.A.E. instead of 15W40
3: Skip[ everything and purchase a new Long Block or even complete motor?

Welcome aboard! Usually the first post seems a little bit happier than this one, looks like you may be posting more often with those symptoms.

May wish to drop the oil pan and see what's in it: engine parts, shavings. Cracked webbing on the block is another favorite.

and unless i'm missing something, he should be putting in a thicker oil not a thinner one!!!!

yes a thicker oil will increase pressure, a thinner will lower pressure

I'd drop the pan just so I could see what down there and how sludges it was and refill it with some thicker oil afterwards Like maybe straight 40 or a 20/50, if you can find it for diesels. Oh course I'd also be shopping around for a engine or rebuild kits for the one I have in the van too. You could get away with rebearing it if nothing else is bad wrong inside.

Thicker oil? Oh ya that will help, help the engine die sooner! Thicker will increase the pressure but will restrict the flow, thinner will flow better with less pressure to lubricate whats needed. Go with a 0-30 or 0-40 synthetic.

Do a search for motor oil on the forum, there's a very in depth thread on oils.

Thicker oil? Oh ya that will help, help the engine die sooner! Thicker will increase the pressure but will restrict the flow, thinner will flow better with less pressure to lubricate whats needed. Go with a 0-30 or 0-40 synthetic.

Do a search for motor oil on the forum, there's a very in depth thread on oils.

i would not go with a 0-30 in the 6.5... when i had my tahoe, i did that once for winter, and that oil was out of there in less than 2000km... when the oil was hot, and accelarating hard, you could some massive bearing knock from the lower end of the engine... dumped it out, filled it up with mobil 1 15w50 and that is what i continued using until i sold it...

i have to disagree with you CR. if he has low pressure we all know that means it's because his clearances have opened up due to wear (or the oil pump is going south). a slightly thicker oil will help take up some of the slack temporarily, definitely not a fix or cure. :(

Right on guybb3 And I did say to start looking for a replacement engine. He could also replace the oil pump while the pan is off BUT that would be a gamble to see if it helps and might be a waste of $$

I'm running Esso XD-3 full synthetic 0:40 right now
Cold Start = 60 PSI Oil Pressure @ idle
Hot Engine = 30 PSI Oil Pressure @ idle

Hot Engine @ 2500 rpm = 50 PSI