Just picked up my car from the first year service at 4k miles. I checked the oil level with oil temp at 160 degrees, level ground, engine running.

Looks to be about 3/8" over the max amount. The dealer tech report shows 8 quarts of oil used- im guessing they put all 8 in instead of the 7.5 recommended.

Is it worth draining the oil ? Can any harm be done at this level?

 

They bill 8 quarts, doesn't mean they put all 8 in however. Dealer can't bill out 1/2 a quart.

They likely put 7.5 in it but perhaps there was some oil that didn't drain all the way out. That or they checked the level wrong and it got overfilled.

 

Recommend you have dealer correct it. Happened on my C7 Z and I brought it back immediate to address.

 

Exactly why I won't let them touch the car. Went to dealership 2 days ago to get oil and filter. Parts manager told me it takes 10 qt.
I pulled it up on my phone and showed him it takes 7.5. The dealers are clueless. When I had my 2016 Camaro. They put in 5 qt instead of 10. Complete morons

 

@Z51CYA I couldn't agree more, even simple oil changes appear to be difficult for these "C8 trained" techs. I won't bore with details but it really makes me consider just dumping the car and going back to Porsche or Mercedes. Its a great car, but to have such lousy service work and apparently inexperienced techs, is not only nervewracking, its just down right disappointing.

 

I worked as a lube tech at a Chevy dealership for a while when I was in auto school. The people that change the oil on all the cars are the least experienced people in the dealership. They put in what the computer system tells them. When I was there I saw a guy over fill a c7 dry sump because he didn't know about two plugs or how to check it. When it came to how much to put back in we used the Prodemand webpage backed by Alldata. Unless someone specifically asked for a main tech and paid the main tech labor rate you got the lube tech 19 year old.

 

If it's over filled and passed the hatch markings on the dip stick remove it ASAP. If you drive the car the connecting rods will aerate the oil .
Took my c8 in last year for it's first oil change.

sucking almost a half liter of oil from the engine.

 

Yep, I would drain.

BTW my 4-volume set of 2014 C7 Service Manuals says clearly what I was taught by my Dad ~70 years ago and always follow. The GM Service Manual States: "The volume in a table is ONLY an estimate. You should check the level and fill under the MAX line."

It's the oil level, wet sump or dry, that is critical NOT the volume ESTIMATE (as the 4 volume service manual states) that is important!

 

The manual is clear about not overfilling it, and yes, I would drain it (I have the equipment to do that). But I do have a question about the urgency of this. The dipstick is measuring the level of oil in the tank, right? Not in the engine oil pan (such as it is - not much to it). And the reason the oil must be measured when the engine is running is that an oil pump in the engine oil pan scavenges the oil and pumps back up into the tank, where it is then distributed back to the engine parts. When the engine is off, I believe some of the oil tends to run out of the tank at the top, so when measured with the dipstick, it appears that the amount of oil in the system is low, when it actually is not. But since the oil level being measure is in the tank, and not the crankcase, what is the harm if there is excess oil in the oil tank? I do know that there is something called a centrifugal oil separator in that tank, and also tube that is part of the PVC system that vents back to a valve cover. If the level in the tank was way too high, I suppose there could be an issue.

Here are some illustrations and a description of the lubrication system. The photos show the tank, and how the dipstick measure the oil level in the tank.

 

^^^^
I can tell you what was wrong if overfilled with the C7 external Dry Sump Tank!

First the oil did drain back, probably past the air/oil scavenge pump gears. Checked when oil was hot BUT with engine off. Had to check after 5 minutes to let the oil drain from the internal baffles BUT not more than 10 or as they stated you got a false low reading. For fun I checked after the car sat overnight with cold oil and it was below the tip, about 5+ quarts low! Some folks said the could hear the oil going back from the pad at the start! Was enough to feed the oil pressure pump.

If it was overfilled (a number of posts where that occurred) there was a hose going from the dry sump tank top to the air intake tube. That is for the air that came in with the scavenged oil. It had to be burped like you burp a baby! EPA says that air contains some oil mist so can't just vent to the air, digest it with the crackcase blowby PCV air and stuff! If overfilled oil went down the air intake tube, soaked the air cleaner and dripped on the ground!

For the C8 the dry sump tank also contains baffles and air that comes in from the 3 oil/air scavenge pumps. Doubt there is a line to the air intake but there are baffles as well as an oil separator that acts as a bit of a catch can BUT has oil that came from the pumps with the air fall back into the tank. Same with some PVC stuff. So not an answer but an indicator of why excess is an issue. Probably not as critical as the C7 or a wet sump (where you need to keep crackcase oil kept below the spinning crack, i.e. why there are pan screens and scampers on my cars) but GM says don't do it so don't!



Don Sherman in an article (Great automotive writer, engineer, race car driver) said this re integrated dry sump tank.

 

[QUOTE=JerryU;1605629992]^^^^
...For the C8 the dry sump tank also contains baffles air that comes in from the 3 oil/air scavenge pumps. Doubt there is a line to the air intake but there are baffles as well as an oil separator that acts as a bit of a catch can BUT has oil that came from the pumps with the air fall back into the tank. .....
/QUOTE]
Jerry, thanks. Here are other lines. As I mentioned in my previous post, in the C8 there is a "centrifugal air/oil separator" tank and a tube (part of the pvc system) that goes from the tank, to the valve cover(s). I did not post images of that, but here they are. And yes, if the oil gets too high, something could go south with that. The centrifugal air/oil separator is item 6 in the image I included in post 9.
Here's the image of the tubing - red is the one that vents the oil tank to the rocker valve covers. The blue on is the one that goes directly to the intake manifold - I think it comes out of the "engine block valley". There is an oil separator there too. One more tube, I did not colorize is the one that gets fresh air from upstream of the intake and to the valve covers. Anyway, overfilling the oil tank will cause issues, but I was curious about how that differed from an overfilled crankcase - and you described some ways. Thanks.

 

Imagine them working on an engine problem with your new Z06? They couldn't even manage to tighten the oil drain plug on my Traverse after an oil change. Drips in the driveway and if it rattled out, guess who would be paying for a new engine! Can't even fathom bringing my C8 in for service!

 

[QUOTE=Andybump;1605630161]That raises some interesting questions and one Tadge in an "Ask Tadge" never addressed in his post on "Catch Cans."
Here is a condensed version:
"To answer the second question first: No, the 2017 Corvette LT1 will not have the Camaro V8 PCV air/oil separator (what the questioner calls a "catch can") added to its oil management system. ...
Even though the Corvette and Camaro share the LT1, they are very different in execution detail. The LT1 in the Corvette sits lower and very close to the ground to enable an industry-leading low profile hood and good sight lines despite a very low seated position. Having the engine close to the ground is great for keeping the vehicle's center of gravity down, but means the oil pan is relatively shallow. Having little depth in the oil pan means it is very challenging to scavenge oil in high G loading conditions. For this reason we add dry sump lubrication to our high performance models. The Camaro's higher engine position allows for a deeper oil pan and a reliable configuration for picking up oil for delivery to all parts of the engine. Thus the Camaro is able to avoid the cost and mass of the dry sump tank and resulting complexity of the lube system.

The Corvette's dry sump tank looks relatively simple on the outside but the internals are really quite complex. The top third of the tank contains a PCV air/oil separation system. …The Camaro V8 PCV air/oil separator is more complex than a "catch-can" since it not only separates oil from PCV air it provides a drain back path for this oil to be reused by the lube system."

The key omission is what were they doing to improve the C7 Wet Sump! Answer is nothing.
Pic below is what they did to "fix" the C7 dry sum in my 2014 Z51 that was just supposed to have mostly a cosmetic issue with "coking" (the build-up of carbon deposits on the intake valve stem in DI engines.) BUT the pic below is what I analyzed on my 2017 Grand Sport that CHANGED PCV system! Frankly was concerned about installing the "Catch Can" I removed from my 2014 Z51 where I was collecting over 1 oz of stuff (mostly PCV crankcase oil mist) but the lines had changed dramatically. In fact, instead of an obvious extra line delivering clean air to the crankcase to purge blowby etc, that line was not there! Had to block that opening in my aFe air intake tube!

Finally figured all the lines out and where the clean filtered air was coming from so I installed the "catch can" as determined it would do no harm (note I just used a one outlet connection in the PCV line to the intake manifold NOT two- don't Track so not needed.) I was collecting less than 1/2 of what I had been so removed it! I'm confident GM did an even better job on the C8. In fact, Tadge's comment about the Camaro having a built-in air/oil separator that returns condensed oil vapors from the crankcase to the oil tank is one thing they have done.

Yep the C8 scavenge pump and PCV system are complex.

The C8 Z06 LT6 engine is even more interesting, at high rpm the oil/air scavenge pumps, have the crack rods and pistons are spinning in ~11 psi of vacuum! Low windage drag. The 6 scavenge pumps in the LT6 are doing far more than putting oil in the dry sump tank!


Also installed a Vacuum/Pressure gauge and defined where the clean air going to the crankcase was located!

 

This is the reason I did the Transmission filter
myself. Not that I wanted to get under the car but wanted the job done correctly. Not that hard just need to work carefully and do it correctly.

 

This is the reason I did the Transmission filter
myself. Not that I wanted to get under the car but wanted the job done correctly. Not that hard just need to work carefully and do it correctly.

 

^^^
Yep up to the C8 did all my own DD oil changes for 63 years! Even my two C7's a 2014 Z51 and 2017 Grand Sport with two years of FREE oil changes. NOT worth the risk to me!

Lucky for the C8 found a small Chevy dealer with a great Corvette Tech. He does everything on Vettes oil changes etc. Watched the ~2 hr process on my 1st last August. He did just what I was taught by my Dad when I was ~10 and what I always do. He underfilled the engine oil slightly using the estimate in a table. Ran the engine to bring the oil to 175 F (he checked the dash display serval times.) Read the dip stick twice (tough to see all new oil on the dip stick, can't trust one reading, I never did!) Since I was standing (mostly outside the open door to the service bay) he showed me the level!

I had him change the DCT filter as well and he did what can't be done on a DIY and specified by GM before the filter change- a flush. Connected to my OBD and GM's Service Computer via WiFi. With the engine running could hear something happening and after ~10 minutes his PC screen said "flush completed" and he changed the filer.

Understand it's not easy but best for folks to check with a local Vette Club, Cars & Coffie etc and see if they can find a quality Vette Tech.

 

Update- I got the car on ramps and drained about 2/3 of a quart. Its now sitting nicely in the hash mark region. Feels a lot better than overfilled. Amazed at how easy it was- just like a gmc acadia or chevy malibu.

 

agree that Porsche service is great, they do what it takes to fix a problem. Routine maintenance is expensive but they do things right. Pack wheel bearings and replace seals with brake job for instance. I am far less impressed with the Mercedes-Benz service I feel that they just gloss things over. I honestly believe that Chevrolet dealers treat the car like any other and are fairly under trained. There may be good Corvette mechanics but I have not found one. I have had my car in at least six times to try to fix the rearview mirror camera and they are unable to do so. Each time I have asked them to change the transmission filter they claimed they could not get one, so I ordered one online and changed it myself.

 

After my first oil change .. I checked the oil level and it was overfilled too. They told me they let it my 2021 Z51 HTC drain for 1 hour, so I suspect the Lube Monkey put in all 8 qts. Had to siphon out about 1/2 qt just as "gpz1000" did.

So on my second oil change I use a different dealership and they didn't over fill, but they must have spilled a lot of oil into the engine bay. The car smelled and smoke would come out of the vent on my HTC when I got home from the dealership. I had to remove the engine cover and use some engine cleaner (orange oil based) to remove the spilled oil. Smelled much better for a few weeks.

I'll be doing my own oil changes from now on...

 

C8 has a dry sump oil system. That means that in theory there is little or no oil in the engine pan. There is no storage in the oil pan. The danger of overfilling was back in the old days when you were actually checking the oil storage level in the oil pan.
Too much oil could splash on the crankshaft causing oil foam. That was the old days. With a dry sump you are checking the oil level in the tank. The tank feeds the pump, nothing else. Do you worry if your windshield washer tank is overfilled?
Of course not, It is just a storage tank and it does not impact the performance of the pump. Same deal with the oil.

This is my understanding of dry sump systems from years of racing. Maybe the C8 is different, but dry sump means no oil storage in the pan. No oil starvation in high G corners and lower ground clearance is possible.
That's why SCCA TransAm cars have dry sumps and only 2.5" of ground clearance. The engine sits really low in the frame, and there is no room under the crankshaft for oil storage.