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Discussion Starter #1
my 5.7 liter has 35 psi oil pressure when cold, as it warms up it drops to 10. i just bought it and have driven it only 10 miles or so until the pressure get to the bottom of the gage. it will rise if i increase the rpms.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Do you have the correct amount of oil in the vehicle? Is it low?

We could also use the vehicle information. Mileage, year, etc.

Change your oil (using a quality filter) and see if your pressures improves.
 

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Discussion Starter #3
yes, it's a 1996 k1500, 5.7 liter, odometer says 160000 miles, changed oil once , have owned it for a month. have only driven it about 50 miles as its not my every day vehicle. i'm considering cutting open the oil filter to see what's in there. its not making bad sounds. also considering installing a mechanical pressure gage. any help will be much appreciated.
 

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What weight oil are you using? Are you using conventional oil, or synthetic. How hot is it in your area. All of this will effect oil pressure. I see mine do the same thing rite now with temps in the high to mid 90s, and I am using 5W30. I really need to switch to 10W30, or 10W40. A thicker oil, will build more pressure. Oh, and I have a 97 Silverado 5.7L with 250,000 miles. My truck runs grate. I bought it used in 2002 with 80,000 miles.
 
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My truck does the same thing. 2005 Silverado 2500HD 8.1L running 5w-30 Mobil 1 full synthetic dexos. AC Delco PF454 filter. Same Hot weather here in south Texas. Starts off cold at about 60 psi and drops to 20 when warm at idle. No issues and no noise.
 

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Hello,
My '93 K3500 was doing the same thing. At start up it was 30+psi and as the engine warmed it dropped to below 10psi. I picked up an oil pressure gauge set and checked it with that. All was fine; ~45psi at cold start, 20+psi at warm idle and 35psi at ~2000 rpm. Turned out to be the oil pressure sending unit on the block. ~$30 part at NAPA . I bought the socket to remove it on Amazon. I was leaning towards the sensor from the beginning as it is a low mileage motor (100K miles) and has had oil changes every 3K miles (or less) since it was new. I had recently replaced the rocker gaskets and the valvetrain was incredibly clean. All told the check and repair took less than an hour.
Not saying this is your issue but something to check.
 

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I'd try putting in a oil pressure sending switch. But you have high miles and you don't know how much care the engine has had over the years. But a rule of thumb is 10 PSI per 1000 RPM, so if at idle ( 700) RPM, you have OK 10 PSI oil pressure, it's OK. Not great but OK ! Everybody have given great advice above.
 

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Discussion Starter #8
thank you to all who have posted. i'm using 5w30 conventional oil right now but will change to a thicker synthetic. and i will go ahead with installing the mechanical pressure gage as i have read that the gage motors can get inaccurate.I live on the san francisco peninsula at sea level, the weather has been in the 80's until the fires caused so much smoke the temperature is down to the 60's.thanks again for the helpful responses! the next problem wi be the brakes.
 

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What weight oil are you using? Are you using conventional oil, or synthetic. How hot is it in your area. All of this will effect oil pressure. I see mine do the same thing rite now with temps in the high to mid 90s, and I am using 5W30. I really need to switch to 10W30, or 10W40. A thicker oil, will build more pressure. Oh, and I have a 97 Silverado 5.7L with 250,000 miles. My truck runs grate. I bought it used in 2002 with 80,000 miles
My 96 chevy c1500 does the same I start and may start with 60 psi and drop to 20 while driving I stop and my gage goes to zero i went to 10w40 and I start at close to 80 when it's hot I have 40 moving at 55mph and 20 at idle mine has 308000
 

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I know which oil and weight can also make a difference but we won't get into the oil debate. For reference, my 98 with a 5.7 normally sits around 60ish on a very cold start and when operating temps it drops to about 20 at idle. Driving at operating temps is around 40. I have used some oils that run a bit lower than that but my normal choices sit around those numbers.
 
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