I just switched from Synthetic Blend to full Mobil One Synthetic. The oil pressure seems to be a little lower using the same weight oil (5w-30). Now I would expect this to be... simply because Synthetic is thinner. I also used motor flush for the first time which made the oil almost like sludge. This is only 2500 miles between last change. Oddly enough, my small amount of lifter knock on my 163,000 mile engine has totally disappeared. The oil pressure warm, at idle is just below the quarter mark. I know the engine is gettin up there in age, but is there anything I can do to raise the pressure some. I don't like it that low. And what causes the pressure to drop in a high mileage engine?

 

The synthetic is not really thinner at operating temps....it just dont thickn up at cold engine temps. Your pressure most likely dropped a bit due to the motor being flushed out. On a 163000 mile engine lower pressure is gonna happen. You may want to at least consider going to a 10w40 wieght oil.....Ild go 20w50.

 

The bearing clearances increase with age, normal wear. That will lower the pressure. You can put a stiffer spring in the oil pump, but that's a lot of work. I would just run a thicker oil. 10W40 should raise the pressure up some. The pressure you are running at idle is pretty much normal. As long as it raises with the rpms, I wouldn't concern myself.

Semper Fi

 

your pressure sounds the same as mine with the same oil at 55k miles...

long as it jumps like it should at WOT you have no problems...

don't switch to a thicker oil unless you gots real problems with leaks and don't have the money to fix em...


your fine

 

Care to explain why ......

 

I have used mobil one 5w30 in my car since I bought it. That is a normal oil pressure for idle. If it doesnt go up like everyone was saying then u got problems. my car has 75k on it now. Been using mobil one since 55k and for 3 years now. Its some damn good stuff. I have heard many testimonials from guys on the board who tore their motors open to stroke them or whatever and that they looked brand new, like they had 500 miles on them when they had like 100k. my .02 Thanks, Michael

 

I too use mobil 1 syn. It is good stuff....My engine looked like brand new (except for the broken pistion..N2O) when we broke it down for machining at 80000miles. The guy stated an observation and I offered a cause and solution. If you are trusting you stock gauge as accurate you are be making a mistake IMO. I do agree that he will be fine running 5W30 , but I would run heavier in his case.

 

Remove the oil cooler (trust me), which allows you to run a much larger filter and also doenst bypass the filter as it used to with cooler, and i went to mobile one 15w-50 from mobile 1 10w40. That got me quite a bit oil pressure.

 

Thats comforting to here, thanks guys. The oil pressure rises to a little above half at WOT, so I'm thinking its good. It may be going higher, but its hard to watch the Tach, Speedo, odometer (and cops) at the same time. The car runs so good for 163,000 miles that it scares me. I mean it runs like a cadillac. I want to stroke it out to a 383, but I just can't bring myself to do it for no reason. I read your oil cooler post atljar, I may take it out to clean it, but no way I'm removing it. What should I use to clean it with?

 

Cleaning it wont do too much good. The way it is set up, the cooler actually bypasses the filter once the filter gets slightly soiled. Rip her off

 

Really? Thats fudged up....

 

sure, anytime...

thicker oil = less thin oil...

thin thin oil + small leak = speaks for itself

the same leaky spot + thicker oil = less leak


thank you, i'll be here all week

 

I recall reading in Mobil 1 literature that oil pressure may drop slightly upon using full synthetic..
I have also noticed a slight drop in a few different vehicles after the switch..
I wouldn't worry about it as long as you have more pressure off idle..

 

Actually at idle that's pretty good pressure. Mine goes down to 10 psi when it's hot and idling in gear. If you are that worried about it, use some 10w30.

John

 

I took mine off.....its basically a POS.