8.1 Oil Pressure - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bpeters5814 · 10-20-2009, 03:32 PM

My grandpa's got a 99 regular cab long bed with an 8.1 It's got about 99000 miles on it and only gets driven about 3500 miles a year (mostly only used to pull a cattle trailer). I was driving it while my truck was in the shop and noticed the oil pressure gauge would be around 40 at startup but drop to 25 and stay there after it warmed up. Is this normal for these motors?

**truckdude239** · 10-20-2009, 04:08 PM

I will look up the recomend specs when I get home tonight

clinebarger · 10-20-2009, 04:38 PM

general rule is 10 PSI for every 1000RPM. 1000RPM 10PSI, 4000RPM 40PSI.

I whouldnt worry about it.

JohnC · 10-20-2009, 05:31 PM

I've heard the 8.1's are really weird when it comes to oil pressure, and oil consumption.

**truckdude239** · 10-20-2009, 05:51 PM

what kind of truck is it none of shop keys list an 8.1L

**truckdude239** · 10-20-2009, 05:55 PM

i firugre 25 psi is about right for idle and hould increase 10 psi for every 1k rpms

bpeters5814 · 10-20-2009, 06:13 PM

Quote:

Originally Posted by truckdude239

what kind of truck is it none of shop keys list an 8.1L

It's a '99 Reg cab 2500HD. Might be a '00. It's one of the first of the 99-06 body styles.

bpeters5814 · 10-20-2009, 06:14 PM

And after it warms up it stays at 25. Doesn't matter what the rpms are. I was wondering if the gauge was goofy or something.

**truckdude239** · 10-20-2009, 07:47 PM

Are you sure it is an 8.1 and not a 7.4 i can not find a listting for the 8.1 under shop key i even calle dmy buddy at the local parts store and the biggest they listed was the 7.4 l

**truckdude239** · 10-20-2009, 07:48 PM

okay i found it they first started putting the 8.1's in in 2001

**truckdude239** · 10-20-2009, 07:49 PM

okay oil pressure at 1000 rpms according to shop key should be a min of 5psi, and at 2000 rpms at 10 psi so your are fine with 25 psi

bpeters5814 · 10-20-2009, 10:13 PM

Quote:

Originally Posted by truckdude239

okay oil pressure at 1000 rpms according to shop key should be a min of 5psi, and at 2000 rpms at 10 psi so your are fine with 25 psi

Sorry about the confusion on the year. Like I said, it's not mine. Just concerned for grandpa... and I'll probably inherit it someday!

Thanks for looking that up for me.

10-20-2009, 03:32 PM	#1
bpeters5814 Registered User Join Date: Apr 2008 Location: Worms, Nebraska Posts: 304	8.1 Oil Pressure My grandpa's got a 99 regular cab long bed with an 8.1 It's got about 99000 miles on it and only gets driven about 3500 miles a year (mostly only used to pull a cattle trailer). I was driving it while my truck was in the shop and noticed the oil pressure gauge would be around 40 at startup but drop to 25 and stay there after it warmed up. Is this normal for these motors?

10-20-2009, 04:08 PM	#2
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,220	Re: 8.1 Oil Pressure I will look up the recomend specs when I get home tonight __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

10-20-2009, 04:38 PM	#3
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	Re: 8.1 Oil Pressure general rule is 10 PSI for every 1000RPM. 1000RPM 10PSI, 4000RPM 40PSI. I whouldnt worry about it.

10-20-2009, 05:31 PM	#4
JohnC Registered User Join Date: Feb 2009 Location: Oklahoma Posts: 7,461	Re: 8.1 Oil Pressure I've heard the 8.1's are really weird when it comes to oil pressure, and oil consumption.

10-20-2009, 05:51 PM	#5
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,220	Re: 8.1 Oil Pressure what kind of truck is it none of shop keys list an 8.1L __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

10-20-2009, 05:55 PM	#6
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,220	Re: 8.1 Oil Pressure i firugre 25 psi is about right for idle and hould increase 10 psi for every 1k rpms __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

10-20-2009, 06:14 PM	#8
bpeters5814 Registered User Join Date: Apr 2008 Location: Worms, Nebraska Posts: 304	Re: 8.1 Oil Pressure And after it warms up it stays at 25. Doesn't matter what the rpms are. I was wondering if the gauge was goofy or something.

10-20-2009, 07:47 PM	#9
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,220	Re: 8.1 Oil Pressure Are you sure it is an 8.1 and not a 7.4 i can not find a listting for the 8.1 under shop key i even calle dmy buddy at the local parts store and the biggest they listed was the 7.4 l __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

10-20-2009, 07:48 PM	#10
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,220	Re: 8.1 Oil Pressure okay i found it they first started putting the 8.1's in in 2001 __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

10-20-2009, 07:49 PM	#11
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,220	Re: 8.1 Oil Pressure okay oil pressure at 1000 rpms according to shop key should be a min of 5psi, and at 2000 rpms at 10 psi so your are fine with 25 psi __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube Last edited by truckdude239; 10-20-2009 at 07:49 PM.



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