Oil related question: don't worry I'm not asking which oil to use
11-04-2018, 04:15 PM
#1
Le Mans Master
Thread Starter
Oil related question: don't worry I'm not asking which oil to use
Hey guys,
Just did an oil change on the 91' Z and I figured I would out myself on how paranoid I may be about this car, so here are a few questions.
I drained the oil after the car sat overnight, then I refilled with 8.5 quarts. Everything seemed to go fine but after checking the dipstick (flat level surface the car is on) it actually seemed to read a bit further past the "full" indicator. I checked it more times than I care to admit and got the same result. I cracked the oil drain bolt and drained out a little to get the film back in the hash mark section of the stick right up to "full". Drained out more than I should have I and slowly added new oil back in, but it's basically back a little above "full" on the stick. I'm not trying to obsessive so if it's fine for it to read above the hash mark, that's fine.
Lastly, the oil pressure readout for the car is a bit wonky. When the car starts up, the oil pressure gauge pegs. As the car warms up and is driven, it eventually comes back around the 40-60 psi area. If I wind up the motor through a few gears, it pegs back at 80 again and stays there long after the short blast is over. It eventually comes back down as I continue driving but it's usually after a few minutes of casual driving. I'm guessing this is the oil pressure sensor going south but wanted to see if this is a common problem with the analogue readout/sensor.
Just did an oil change on the 91' Z and I figured I would out myself on how paranoid I may be about this car, so here are a few questions.
I drained the oil after the car sat overnight, then I refilled with 8.5 quarts. Everything seemed to go fine but after checking the dipstick (flat level surface the car is on) it actually seemed to read a bit further past the "full" indicator. I checked it more times than I care to admit and got the same result. I cracked the oil drain bolt and drained out a little to get the film back in the hash mark section of the stick right up to "full". Drained out more than I should have I and slowly added new oil back in, but it's basically back a little above "full" on the stick. I'm not trying to obsessive so if it's fine for it to read above the hash mark, that's fine.
Lastly, the oil pressure readout for the car is a bit wonky. When the car starts up, the oil pressure gauge pegs. As the car warms up and is driven, it eventually comes back around the 40-60 psi area. If I wind up the motor through a few gears, it pegs back at 80 again and stays there long after the short blast is over. It eventually comes back down as I continue driving but it's usually after a few minutes of casual driving. I'm guessing this is the oil pressure sensor going south but wanted to see if this is a common problem with the analogue readout/sensor.
11-04-2018, 04:26 PM
#2
Melting Slicks
Rarely can I ever get over 7.5 quarts in after an oil change, unless I leave it drain for hours.
Next time, stop at 6 quarts, wait 10-15 minutes and see the level.
Add 1/2 quart, then less, until you get to the full line.
Cold engines will always put the gauge nearly to the top upon startup until warm.
40-60 is fine.
I do not like the 80 peg after a romp.
Yes, you may be getting ready for a new sender.
Relax and have some fun with your new toy!
Marty
Next time, stop at 6 quarts, wait 10-15 minutes and see the level.
Add 1/2 quart, then less, until you get to the full line.
Cold engines will always put the gauge nearly to the top upon startup until warm.
40-60 is fine.
I do not like the 80 peg after a romp.
Yes, you may be getting ready for a new sender.
Relax and have some fun with your new toy!
Marty
11-04-2018, 06:53 PM
#3
Le Mans Master
Thread Starter
Rarely can I ever get over 7.5 quarts in after an oil change, unless I leave it drain for hours.
Next time, stop at 6 quarts, wait 10-15 minutes and see the level.
Add 1/2 quart, then less, until you get to the full line.
Cold engines will always put the gauge nearly to the top upon startup until warm.
40-60 is fine.
I do not like the 80 peg after a romp.
Yes, you may be getting ready for a new sender.
Relax and have some fun with your new toy!
Marty
Next time, stop at 6 quarts, wait 10-15 minutes and see the level.
Add 1/2 quart, then less, until you get to the full line.
Cold engines will always put the gauge nearly to the top upon startup until warm.
40-60 is fine.
I do not like the 80 peg after a romp.
Yes, you may be getting ready for a new sender.
Relax and have some fun with your new toy!
Marty
Last edited by 1985 Corvette; 11-04-2018 at 06:55 PM.
11-04-2018, 07:49 PM
#4
Tech Contributor
Just drive it......a bit over fill will not bother anything and 80 psi on start up back to 60-70 after it warms up is very normal at say 2,000 rpm...….lower end of 40-70 at idle is normal. You are a bit obsessive 
Another way to look at it
You might be surprised when the engine is running the oil level is a bit below the hash mark on the dip stick. Oil sitting above that mark is no big deal.
A few minutes of casual driving is not enough to warm up the oil to where it might effect oil pressure. If the oil pressure eventually goes down, you are in fine and I would say normal shape
You might also be surprised how low your oil level can be on the dipstick as long as you have oil pressure and be fully operational (but do not go to long with low oil simply because low oil volume means hotter oil).
I have never heard of engine failure because of oil overfill but maybe something going on with several quarts over fill like disturbing the oil pick up with highly air entrained oil
Post 3 - LT5/ZR-1 Fluids
Another way to look at it
You might be surprised when the engine is running the oil level is a bit below the hash mark on the dip stick. Oil sitting above that mark is no big deal.
A few minutes of casual driving is not enough to warm up the oil to where it might effect oil pressure. If the oil pressure eventually goes down, you are in fine and I would say normal shape
You might also be surprised how low your oil level can be on the dipstick as long as you have oil pressure and be fully operational (but do not go to long with low oil simply because low oil volume means hotter oil).
I have never heard of engine failure because of oil overfill but maybe something going on with several quarts over fill like disturbing the oil pick up with highly air entrained oil
Post 3 - LT5/ZR-1 Fluids
Last edited by Dynomite; 11-09-2018 at 10:09 PM.
11-04-2018, 08:32 PM
#5
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Last edited by FASTAZU; 01-07-2020 at 05:15 PM.
11-05-2018, 05:56 AM
#6
Le Mans Master
you are fine, just remember to let the car sit for a long time before checking on the dip stick. Drain back takes 15 min or more. I like to let it sit for an hour after starting.
if you check right after starting and idle, it will show about a quart low.
if you check right after starting and idle, it will show about a quart low.
11-05-2018, 09:42 AM
#7
Drifting
My preference for checking fluid levels is much like a pre-flight check. After the car has been sitting overnight, do a walk-around, pop the hood & check fluid levels. Everything is drained back & cold.
For an oil change, do it on a weekend when you can pull the drain plug & let it drain over night. Next morning, change the filter, put the drain plug back in & add 8 qts & drive. Check oil level the next morning & add as needed from what is indicated on the dipstick. It's useless to add half a qt & right away pull the dipstick to check where it filled to. The LT5 is a very slow drain-back engine. **** is OK, part of the fun is to pamper & enjoy.
As an aside, I once had a complete LT5 on a stand. I drained the oil overnight, but left the plug out. Oil dripped into a pan under the engine for over 2 years, until I finally gave up & plugged it. Not a lot mind you, but just never did quit. Crazy.
For an oil change, do it on a weekend when you can pull the drain plug & let it drain over night. Next morning, change the filter, put the drain plug back in & add 8 qts & drive. Check oil level the next morning & add as needed from what is indicated on the dipstick. It's useless to add half a qt & right away pull the dipstick to check where it filled to. The LT5 is a very slow drain-back engine. **** is OK, part of the fun is to pamper & enjoy.
As an aside, I once had a complete LT5 on a stand. I drained the oil overnight, but left the plug out. Oil dripped into a pan under the engine for over 2 years, until I finally gave up & plugged it. Not a lot mind you, but just never did quit. Crazy.
11-05-2018, 09:47 AM
#8
Drifting
Many moons ago, there was a thread on the Corvette Forum about an owner who took his ZR-1 to a dealership that performed a slam-bam, thank you ma'm oil change that resulted in a broken crank. I don't remember all the details now.
11-09-2018, 09:16 PM
#9
Le Mans Master
Thread Starter
Thanks guys. I let a little oil out and tightened the bolt back up. And then I found out the dipstick gets seated and immediately pulled out...to which I found the actual level within the hash marks. I was seating the dipstick and oil was getting on the area just above the area for reading and bleeding down onto the actual reading making it look like way more was in it. Of all the cars I've had, this is the first one I've had do this with the dipstick. So I've got it where I want it on the readout.
I guess I've wanted one for so long I'm in the, "Don't **** anything up you just got it!" phase. As an aside, I will say this: someone gorilla armed the oil pan drain bolt on, to the point that I had to use several extensions and a breaker bar on the ratchet wrench to break it free. I was just waiting for the threads to flush out with the oil but it seems to have stayed intact. I used a fiber washer (should've asked/read here first) but I still had an ever so small drip. Nothing major, a few drips on the floor over 5 days of just sitting in the garage....but enough to make me crazy. So I used a 9/16 wrench and gently applied as much twist as I felt comfortable giving to further tighten the bolt down.
I'll keep track of how that does but is there a particular washer you guys run on the bolt to keep it drip free? I had an OEM oil pressure sensor come in from Jerry's so I'll install that this weekend.
I guess I've wanted one for so long I'm in the, "Don't **** anything up you just got it!" phase. As an aside, I will say this: someone gorilla armed the oil pan drain bolt on, to the point that I had to use several extensions and a breaker bar on the ratchet wrench to break it free. I was just waiting for the threads to flush out with the oil but it seems to have stayed intact. I used a fiber washer (should've asked/read here first) but I still had an ever so small drip. Nothing major, a few drips on the floor over 5 days of just sitting in the garage....but enough to make me crazy. So I used a 9/16 wrench and gently applied as much twist as I felt comfortable giving to further tighten the bolt down.
I'll keep track of how that does but is there a particular washer you guys run on the bolt to keep it drip free? I had an OEM oil pressure sensor come in from Jerry's so I'll install that this weekend.
11-09-2018, 10:00 PM
#10
Tech Contributor
Oil Pan Drain Plug and Bonded Washer
Bonded Washer
Last edited by Dynomite; 11-10-2018 at 04:08 PM.
11-10-2018, 10:46 AM
#11
Le Mans Master
Thread Starter
That bonded washer is the exact washer that came off the car when I changed the oil....meaning this oil hasn't been changed since the 3rd owner had it. Yikes. 3rd owner had it listed for sale at 78,300 for mileage, and I got it from the 4th owner with 81,000 on it. Oil definitely looked overdue for a change. Looks like Jerry is getting more of my money! Thanks, Dynomite!