Adam_W

There are likely two issues going on, but here are the facts:

2008 Z06, about 12,500 miles. Daily driver, no track time.

Most recent oil & filter change was 5 months ago: 8 quarts of Mobil 1 5w-30, performed by trusted mechanic

Recently, oil pressure gauge will suddenly drop down to zero with "low oil pressure" indicator beeping on DIC, just for moment; then, just as quickly, the pressure rises back to normal. This has happened maybe 3 or 4 times. During these occurrences, the engine sounds normal. Seemed like a glitch with the sensor, rather than actual intermittent loss of oil pressure.

On startup in the morning, when oil temp is 95 degrees, oil pressure at idle is around 50-60.

After driving around, when oil temp has been 180-190, oil pressure at idle might be 30-35.

(I'm assuming these oil pressures are normal.)

I decided to check the oil level according to the manual: I drove the car about 15 minutes, and oil temperatures had reached around 180-200 degrees.

The manual says to check the dipstick between 5 and 20 minutes after engine is turned off. I checked at 8 and 13 minutes. Both times, I wiped the dipstick clean, plunged all the way in for a moment, then pulled it back out and looked: completely dry. Can't imagine I'm doing this wrong.

Later in the day, I repeated the whole process, i.e. also after driving it around a bit (oil pressure readings on DIC were the same as above during my drive). Result was the same: at around 8-12 minutes, dipstick was completely dry.

What's the deal? Could the oil level be so low that the dipstick is dry, and yet still be "high enough" to give the above pressure readings? If that's that's the case, why would it be so low, i.e. no obvious oil leak? Should I be adding some oil?

Thanks!

TT32VGT

if it doesnt show up on the dipstick after getting to 180+* and waiting for 10min or so after, then yeah def add oil.

keep an eye on it

Bill Dearborn

The engine can run fine at low rpms with a fairly low oil level. Not sure how low the level has to drop for it to cause an immediate issue but I would check the level again and then slowly add a quart of oil. Put in half, wait 30 seconds and then check the dipstick to see if you a reading. If you don't see anything add the rest. Step and repeat until you see oil on the dipstick and then add enough oil to bring the level to the top dot on the dipstick. You may have to restart the engine and bring the oil back up to temperature every now and then if you take too long doing this. I have a funny feeling your trusty mechanic may not have put in all of the oil required.

Bill

2StrikeHtr

Yes, this can be the case. The fact that you had some issues 3 - 4 times after the oil change by your mechanic would concern me. Over some 35+ years that I've wrenched on cars and hung around shops I've seen more than one "reputable mechanic" loose track of how many quarts he's added. Could just be that simple, that you're a quart short.
It's good to either do as much of your own work on your Z as your talent and tools allow, or incessantly check after who does. Not saying he's a bad guy - anyone can loose count.

Most importantly, I'd check thoroughly and frequently for any leak anywhere. I think you've gotta add oil, just don't overfill.

I've also seen on the Forum that some guys Z's take more than 8 quarts - mine included. Check it the way the manual says and add it carefully to the line.

AzDave47

In 2008 some Z's had the 8 Qt system and some had an 8 1/2 Qt system. From what you've described it seems you have low oil level and (hopefully) no oil system problems.

Per Bill, put in a 1/2 qt and then check it. If still not on the stick or below the hatched area, add the other half. If it still seems low, drive the car, get the oil to 175* and then do the level check at 5+ minutes. If it still needs oil, follow the procedure above and have a serious discussion with your "trusted" mechanic.

Adam_W

Thanks for the advice everyone.

So put in half a quart this morning, drove it around for 20 minutes until oil temps were 190 for a while, then parked at work, waited 10 minutes, and rechecked: wiped dipstick comes back up dry, no oil on it.

I put another half quart in it.

Will check again when I get home and add another half quart if dipstick still shows no oil.

50 4Ever

My 2008 used to burn oil, 5 quarts between oil changes based on the oil life indicator. The hatch marked area is 1 qt. Check it 5 minutes after shutdown, oil should be at top of hatch marked area. If the level is at the bottom of the hatch marked area you are 1 qt low. If you wait longer than 5 minutes, the oil slowly drains back into the pan and won't give you an exact reading. So a full sump will read at the top line after 5 minutes and at the bottom line after 20 or 30 minutes.

My Z is the 8 1/2 qt model and I hardly ever get it full from the dealer. They see its a 2008 and assume it is an 8 qt model. The service area has the ability to enter the vin into VIS, I think, and get all the capacities for that vin. But, most are too lazy.

Once you get the sump full, check the oil level every time you fill up with gas, and record it just to see if it is burning oil. My valve guides were shot, after they were replaced my oil consumption problem disappeared...

cclive

That's scary to see a dry dipstick...sounds like the mechanic may have put in 5 rather than 8, but I would still expect him to have checked the dipstick to fine tune the level. At idle and low rpm, the level would be OK to keep the pressure up but when the rpms go up, the pump will start sucking air for a short time...not good.

Mark2009

That's an interesting tidbit, thanks for sharing!

MarMPB

That just happened to me! 2010 Z06 with 10K miles.
But I'm blaming myself too for being negligent. My trusty mechanic changed my oil and oil filter and I assumed it was ok.
So I failed to check the oil level for several months, because I almost didn't drove the car ( 1000 miles max ) and almost always at low rpm.
Yesterday, I decided to check it for a future weekend trip and saw my dipstick dry!
I had to add 2qts to the oil shows at the very tip of the dipstick!
Then I add another 1 quart and went for a drive to do the manual procedure. The level went up but not close yet to the min checkered area.
The manual says in that case to add at least 1 quart more. I had to put 2 more quarts to get to the top hole of the the dipstick!
There is no signs of oil leak, no high temps, no warning msg/lights, nothing abnormal.
So, I'll go on to my fairly long weekend drive and keep close attention to the oil level to see the consuption.
But I can't stop thinking if I might have damaged the engine of the poor car

RAGGDOLL

I wouldn't be driving that car until the oil level read normal on the dipstick. If it was me, i'd dump the oil (measuring what comes out) and add 8 quarts.

3LZZ06

Your car has a 10.5 qt system so by having to add 5 qts you still had 5.5 qts left.

I wouldn't worry about any damage with 5.5 qts and just easy street driving.

Your friendly neighborhood oil monkey obviously put 5 qts in your last oil change.

I just wouldn't trust anyone to do maintenance I can easily do myself. If you have no choice but to have someone else do it, just check it carefully before you leave.

AzDave47

OP - any update?

Adam_W

Following the manual procedure, I've added a total of 2 quarts and dipstick still dry.

Because I'm worried that there is something weird going on causing the dipstick reading to be erroneous - and I don't want to accidentally overfill the oil, which I know is bad - I took it the dealer service department.

They have a decent reputation among corvette owners, and filling up engine oil is not exactly a hard task. Will let you guys know when I find out from them.

AzDave47

Did you talk to your trusted mechanic to ask him how much oil he put in?

383vett

I would just keep adding oil until the level is normal. If it takes 2 or 3 or 4 quarts, so be it.

Adam_W

hey, you are from Moraga. I was once engaged to a girl from Moraga. Pretty area, pretty girl.

MarMPB

No update?

Well, about the dry dipstick in my 2010 Z06 like in Adam's car I had to add 5 quarts to get to the top dot of the checkered area.
I checked that a few times and it was ok.
So I went to a 1000 miles total road trip with a 3 KM airstrip top speed race in the middle and did very well.
I checked the oil level many times in the weekend and after returning home.
No visible oil consumption!
It's clear to me now that the shop really did a lousy job but thanks God everything seems ok.

cwcrash

I had dealer change my oil just before the 50th anniversary tour and did not check the level. after first day of driving I check the level of my 2000 covert,no oil showing. I freak out thinking I had motor problems, after 2 quarts it was back to normal. my lesson was and is never assume it was done correctly. dealer put five quarts instead of seven+

Adam_W

Sorry for the delay in update, guys. Was on-call over the weekend and busy with work.

So here's what happened:

I took it to Connell Chevrolet. They said the oil was low and they just drained it and refilled it with 8 quarts, since I have some maintenance plan that comes with Certified PreOwned. They said that I better check with my trusted mechanic, as the oil shouldn't be this low in 5 months after being changed.

I called my trusted mechanic, who is someone well known on this forum, and he looked at his notes and reassured me that he put in 8 quarts on what day. He said there is no way that he underfilled it.

When I brought up the issue of 8 quarts and 8.5 quart capacity, he was all over it and was familiar with it.

I guess - ultimately - I still trust him that he knows what he's talking about. He works almost exclusively on Corvettes.

I'm wondering if I'm burning oil because of valve guide wear.

Anyway, I'll keep a close eye on it and if I'm indeed burning oil, I'm thinking that I might get the wiggle test done. If the oil level stays up over time, I'll chalk it up to my mechanic having lost count of how much oil he put in back in January. Hopefully that's the case, because I don't want to heads redone before GMPP is up.