Just drained 10 quarts of oil from my L8T

[BuckWallace]

So, I had two free oil changes from my dealer and just did my first post-break in oil change myself. I went to drain my oil catch pan into some milk jugs and filled up 2.5 jugs, which comes out to about 10 quarts. Sure enough, the L5P Duramax takes 10 quarts, so now I'm worried the dealer put in 15W-40 instead of 5W-30, not to mention the two extra quarts.

 

Anyway, I put 5k miles on the truck with the extra 2 qts—should I worry about any potential damage caused by this? I'm also going to send off a sample to Blackstone to test the viscosity. 

Edited March 6, 2025 by BuckWallace

[CamGTP]

I wouldn't worry to much about it. Even though the engine holds 8 quarts, there is never that much in the sump at any given time unless the engine is off. There will always be 2-3 quarts being pumped through the engine and running down back into the oil pan. Even with the extra quarts of oil the level isn't high enough for the crank to start smacking the oil causing it to foam up.

 

Hard to say what oil they actually put it in though. Could have been the correct oil or could have been 5W40 or 15W40.

[Z45]

How do you come with 2 extra quarts?   It takes 10 and you drained 10..

 

15W-40 is the correct viscosity, not 5W-30. 5W-30 is for the 6.6L GAS engine.

Edited March 7, 2025 by Z45

[BuckWallace]

I have the L8T gas engine, which takes 8 quarts of 5W-30.

Edited March 7, 2025 by BuckWallace

[Z45]

You never mentioned what engine you had so when mentioned Duramax I assumed thats what you had?

 

Well you changed the oil now so is your word against theirs and I would bet they won't believe you?   Risk you take trusting the dealer.  At least they did not forget to put oil in. Happened to a lady I know, she made is 5 miles.

Edited March 7, 2025 by Z45

[BuckWallace]

37 minutes ago, Z45 said:

You never mentioned what engine you had so when mentioned Duramax I assumed thats what you had?

 

Well you changed the oil now so is your word against theirs and I would bet they won't believe you?   Risk you take trusting the dealer.  At least they did not forget to put oil in. Happened to a lady I know, she made is 5 miles.

Yeah, well I'm posting in the L8T section and just mentioned the Duramax to possibly explain why they put 10 quarts in. I still have the used oil, so technically I could prove it's all the same stuff.

[bruceb58]

1 hour ago, Z45 said:

You never mentioned what engine you had so when mentioned Duramax I assumed thats what you had?

The title of the thread says L8T unless he changed it.

Edited March 7, 2025 by bruceb58

[Pryme]

Happened to me with my daily driver Corolla. The 1.8 holds 4.4qt and the now more common 2.0 holds 4.9 and I drained 5 out of it. Oil change techs are basically fast food level. 

[BuckWallace]

55 minutes ago, Pryme said:

Happened to me with my daily driver Corolla. The 1.8 holds 4.4qt and the now more common 2.0 holds 4.9 and I drained 5 out of it. Oil change techs are basically fast food level. 

Yeah, I've done my own changes my entire life until I started buying new vehicles and got the 1-2 first free oil changes. That's what I get for not checking their work before I drove it home...

[PunchT37]

I`ll be curious to see the uoa on that thing.

[Pryme]

30 minutes ago, BuckWallace said:

Yeah, I've done my own changes my entire life until I started buying new vehicles and got the 1-2 first free oil changes. That's what I get for not checking their work before I drove it home...

Exactly my case too. 

[Another JR]

When your dealer installs the temporary license plate on your new truck with an impact driver, you don’t go back for the “free” oil change. 

[Pryme]

8 hours ago, Another JR said:

When your dealer installs the temporary license plate on your new truck with an impact driver, you don’t go back for the “free” oil change. 

I draw the line at a 36” pipe wrench with a 6ft pipe slipped over for more leverage. 

[BuckWallace]

All I know is if I put 10 quarts of the wrong oil in my engine and needed warranty work, I'm sure GM would gladly deny my claim.

[Chuck FB]

17 hours ago, BuckWallace said:

Yeah, I've done my own changes my entire life until I started buying new vehicles and got the 1-2 first free oil changes. That's what I get for not checking their work before I drove it home...

New member here, I decided to sign up after some months of reading mostly through this particular GM forum since its official that I bought the truck I had ordered back in Oct and have it in my possession for over a week now. I believe I will have two free engine oil changes available to me within the next 12 months but I am one that is leery about bringing a perfectly good operating vehicle to a shop, certainly not some shady oil change place. Unfortunately even dealerships are not immune to screw ups as after all the people in the oil change bays are from what I understand anyway as typically new hires with often minimal if any experience prior, nor are they mechanics but they may have desires to go into that trade. 

 

If you kept that old oil filter, hang onto it as well as the used oil but don't cut it open. Get that oil sample done and back into your hands and then go from there. My fear and don't mean to go fear mongering, but lets say it turned out to be diesel rated 15W-40, it in theory may have a higher additive package as per zinc etc that could cause low speed pre-ignition that the Dexos 1, Gen 3 oil is designed to prevent. At this point one can just hope its the correct oil but with two quarts excess, otherwise if not its to the dealer to explain what was found in your engine and a course of action they would take.

 

Speaking about oil levels on my new truck, again because of this forum talking about their findings with some fluids being low from new, I went over my truck to check things out. Before it had left the dealer I happened to talk to the service manager who's background is a GM mechanic ( but I had never met him officially until that moment ) and we were talking about some of the issues with vehicles in general in the last few years, yes the valve body issue in the 10 speed HD etc and he said they had a couple of rear diffs/wheel bearing ends blow up on them a couple of years ago due to too low a factory fill and claimed that now they make a habit to check the oil levels. Now granted maybe he thinks they are doing that when bringing in new trucks but sadly my truck proved otherwise or mine slipped through the cracks. Engine compartment wise accessed fluid levels were all good as per engine oil 1/8" above full, brake fluid full, power steering fluid in the middle of range, coolant good. However the rest of the driveline varied and of course a pain in the butt to do the auto trans but did that as well just to be sure. All levels taken on a flat shop floor with fluids having sat over night ( other than the auto trans check which is done hot ) using a wire bent at 90degrees and measuring tape.

 

Front diff ; 1/2" low

Auto trans ; right on level after a whole procedure ( can explain that after )

Transfer case ; approx 3/8" low and also measured what I had to add which was about 200 ML

Rear diff ; exactly 1" low ( for F's sakes ... )