The vehicle with a problem is a 1992 GMC Sonoma 4.3L V6 with 108,000 miles on it. As I have posted on the other forums before this truck was purchased new by myself in June 1992 and for the first 100,000 miles or so used Pennzoil 5W30 or Goodwrench (Mobil) 5w30 conventional oil. The last couple of years the truck hasn't been driven but for only 8,000 miles or so and I have been trying to keep it in good shape--it still runs like brand new. I have used Schaeffer's 7000 10w30 in it the past three oil changes and although the engine probably isn't dirty I decided I would purge it with Neutra anyway. I have always used either AC Delco PF52, or Carquest/Napa/Wix filters with a few PureOne's throwed in on a couple of changes. Now to the problem. The truck has always held good oil pressure 30-40 at idle and 50-60 approx. at highway speeds. I had a Mobil 1 filter left over from my collection of filters for my car that I decided I would use with my Neutra purge. I removed my Wix 51036 filter and replaced it with the Mobil 1 M-201 which I filled with oil. I then added a 12oz. bottle of Schaeffer's Neutra, started the truck, checked for leaks and oil pressure, and everything seemed OK. I decided to take the truck on a rare road trip and it drove fine--I would guess the trip to be 120-130 miles. I stopped to fill up with gas when I got back to town and upon leaving the gas station I noticed that my oil pressure had bottomed out. At 35mph I was only showing approx. 10-20 lbs. of oil pressure. I "stepped" on it a little bit up to around 50mph and only managed to reach 30 or so lbs. of pressure. I thought that maybe the restrictive MObil 1 filter might be the ailment so I went home and replaced it with an AC Delco PF52 but the pressure still is unchanged. Sorry for the length of this post but I am completely puzzled because of this. If anybody has any ideas please try and help me out. Thanks in advance.
Oil pressure drop in 4.3L V6 GMC Sonoma
- Thread starter liquidballbearing
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use a mechanical oil pressure to test the pressure maybe the sender or gauge hopefully is bad,
Try cleaning and tightening the wire connection to the oil pressure sender. Hopefully that's the trouble.....
For some reason I have noticed an Idle pressure oil drop using both Mobil 1 and Royal Purple.
My guess assuming my oil pressure guage is ok.
These oils seem to run quiete thin when hot.
Could this be the culprit.
My gut instinct says Dinos tend to hold thier thickness better at temp.
I am basing this on Mobil 1 SuperSynthetic 5W30 and Royal Purple 5W30 respectively.
hmmm...maybe i'll go back to 10W30 year round, I still don't have the courage to switch to 10W40 *lol*
My guess assuming my oil pressure guage is ok.
These oils seem to run quiete thin when hot.
Could this be the culprit.
My gut instinct says Dinos tend to hold thier thickness better at temp.
I am basing this on Mobil 1 SuperSynthetic 5W30 and Royal Purple 5W30 respectively.
hmmm...maybe i'll go back to 10W30 year round, I still don't have the courage to switch to 10W40 *lol*
It concerns me that it lost pressure suddenly, and not at the oil change time. I would wonder if some sludge loosened by the neutra clogged the oil pump pickup screen.
On a long shot, does the oil seem to have lost viscosity? Don't know this engine, but I once lost oil pressure and had a tough time finding the cause. Turned out mechanical fuel pump was leaking large quantities of fuel into the crankcase.
On a long shot, does the oil seem to have lost viscosity? Don't know this engine, but I once lost oil pressure and had a tough time finding the cause. Turned out mechanical fuel pump was leaking large quantities of fuel into the crankcase.
MolaKule
Staff member
Liquid,
Maybe it's time to move up to 10W30 or 5W40 since the clearances may be getting larger.
Myself, I have not seen any oil pressure drops on any synthetic fluids in my '92 Suburban 350 V8 with mileage - 271,000+. Currently, I run 10W30's in the winter (Amsoil 10W30 ATM) and 10W40's (Modified Delvac 1) in the summer. The engine was originally speced for 5W30's when new.
for filtering, I use either SDF23's or the SuperTech equivalent, depending on what I have on hand.
[ June 04, 2003, 05:56 PM: Message edited by: MolaKule ]
Maybe it's time to move up to 10W30 or 5W40 since the clearances may be getting larger.
Myself, I have not seen any oil pressure drops on any synthetic fluids in my '92 Suburban 350 V8 with mileage - 271,000+. Currently, I run 10W30's in the winter (Amsoil 10W30 ATM) and 10W40's (Modified Delvac 1) in the summer. The engine was originally speced for 5W30's when new.
for filtering, I use either SDF23's or the SuperTech equivalent, depending on what I have on hand.
[ June 04, 2003, 05:56 PM: Message edited by: MolaKule ]
Thanks guys!! Sorry I haven't posted earlier but I was in Fayetteville, Arkansas Tuesday thru yesterday and couldn't get on the net. I will look into each of these but may change the oil first since it's the easiest to do. Thanks again.
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