Sludge?
Thread Starter
Pro
Joined: Oct 2013
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Sludge?
A Tiktok garage shop notes engine oil sludge buildup in many cars that had 8000 to 10000 mile oil changes, and obviously recommends more frequent oil changes.
Is this a concern for C8s or does Mobil 1 Supercar oil prevent sludge buildup between yearly/7500 mile changes?
Is this a concern for C8s or does Mobil 1 Supercar oil prevent sludge buildup between yearly/7500 mile changes?
Popular Reply
Sep 10, 2024, 11:46 AM
Drifting
Joined: Mar 2016
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From: Glenelg MD
Instructor
Joined: Nov 2023
Posts: 209
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1. How you drive the car (distance and load)
2. The oil you use
3. The total time between oil changes (extreme example More than 1 year between changes)
There is a ton of missing information regarding heat cycling, engine type, etc. The best way to know for sure in your car is to do an oil analysis. Otherwise a good rule of thumb is use the oil recommended in your owners manual and change your oil AT LEAST once a year.
Race Director
Joined: Jan 2014
Posts: 10,709
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From: Fulshear, TX
Could they perhaps just be looking for clicks/views and/or trying to sell you something? GM does a very good job of laying out oil change requirements in the owners manual (hint: they're not 8-10k mile intervals), meanwhile Mobil 1 designed a very robust oil pack with ESP/Supercar.
Thread Starter
Pro
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The shop is top notch and shows the engines with sludge. Every single one followed the manufacturers recommended oil change schedule. To say GM knows what they are doing is an incomplete answer - any maintenance including the oil change schedule is to avoid warranty costs, not provide longevity.
Last edited by davelv; Sep 10, 2024 at 03:56 PM.
Race Director
Joined: Jan 2014
Posts: 10,709
Likes: 7,101
From: Fulshear, TX
The shop is top notch and shows the engines with sludge. Every single one followed the manufacturers recommended oil change schedule. To say GM knows what they are doing is an incomplete answer - any maintenance including the oil change schedule is to avoid warranty costs, not provide longevity.
What vehicles?
Which engines?
What were the driving conditions?
How many miles on them?
What oil was run in them?
What filters?
If I had to guess, I bet you're referring to Ford Boss Me...
Le Mans Master
Joined: Feb 2008
Posts: 5,634
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From: Lake Worth Beach, Florida
I can say that I owned my C6 for 16 years 181,000 miles and near the end of my ownership I had to remove the intake and I found no sludge of any kind in the top of the engine. I generally changed my oil around 6,000 to 7,500 miles based on my oil life indicator. I always used the proper Mobile One as prescribed by GM.
I also had to replace the valve cover gaskets and again found the top of the heads to be perfectly clean.
I also had to replace the valve cover gaskets and again found the top of the heads to be perfectly clean.
Last edited by Rocketmanwpb; Sep 11, 2024 at 10:19 PM.
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Drifting
Joined: Jul 2012
Posts: 1,270
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From: Kiln MS
It’s a personal preference but I would never let 10k miles go between oil changes. And theres a lot of manufacturers that recommend up to ten thousand miles between oil changes. Toyota being one of them. They recommend this but I change mine every 5k miles. To me this is simply asking someone to pay for a new engine replacement somewhere after a 100k miles. After the warranty is gone on a car any major repair is the responsibility of the owner. Oil is cheap engines…. Transmissions and rear diffs are not.
Melting Slicks
Joined: Jan 2006
Posts: 2,298
Likes: 1,860
From: Oregon
That is a good question. 10K on a daily driver that gets a lot of short drives may collect a lot of condensation.
Or a car that never gets the oil temp hot, or never runs at high rpm. IMO it's the short runs that cause problems.
I only drive 3-4K per year so a change once a year solves that problem, and I always go for at least half an hour cruise.
But that's my pampered life. If you are using your C8 as a DD with short drives, change that oil.
8K oil change always sounded extreme to me, even on the wife's mini van.
Or a car that never gets the oil temp hot, or never runs at high rpm. IMO it's the short runs that cause problems.
I only drive 3-4K per year so a change once a year solves that problem, and I always go for at least half an hour cruise.
But that's my pampered life. If you are using your C8 as a DD with short drives, change that oil.
8K oil change always sounded extreme to me, even on the wife's mini van.
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
Posts: 34,939
Likes: 12,352
From: NE South Carolina
The shop is top notch and shows the engines with sludge. Every single one followed the manufacturers recommended oil change schedule. To say GM knows what they are doing is an incomplete answer - any maintenance including the oil change schedule is to avoid warranty costs, not provide longevity.
- First, miles was a poor way to determine oil life! But that and time were all we had. Where they good highway miles or poor stop and go, many cold starts city miles? See Pic from my 1993 Vette BEFORE Vettes had OLM.
- BTW recall in ~1955 my Uncle who was Service Manager at a large Chevy dealer told me that when my we were picking a car for my Dad from a large lot of 2-year-old fleet cars they just received.
- Reviewing just one key item. The OLM monitors oil temp after cold starts. Lots of blowby for a few minutes after cold starts that has the rich fuel/air mixture passing the cold piston into the oil. The main product of combustion is Water. Yep, CxHx plus Oxygen in air combusting makes heat and water, H2O etc.
- After a few minutes the ~2500F combustion temps heat the pistons and they expand reducing the piston to cylinder wall gap. Far less blowby.
- If the oil gets hot enough long enough it will evaporate much of the water in the oil. With many mostly short trips the OLM will reduce the 12 months minimum change time.
- That water forms things like sulfuric acid that eats metal with the car parked,
- BTW my 1988 Vette like all 6 others stated you must change oil a minimum of every 12 months. Yep if you only drive~3000 miles/yr like myself must change in 12 months NOT that the oil is worn out it's for contamination.
- The OLM is a complex algorithm, and miles is just one of the things it measures, total engine revolutions, used for airplane engines, stationary power is another. Lots of info on the subject and a very long post I could add but this is more than most can digest!
Last edited by JerryU; Sep 11, 2024 at 07:18 AM.
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
Posts: 34,939
Likes: 12,352
From: NE South Carolina
Suggest stop 2nd guessing the engineers. It's how you drive that is the issue. Heck some oils advertise good for 15,000 miles. Yep, if all highway, minimum stops probably could be fine. Read up on the OLM which is far better than guessing!
Thread Starter
Pro
Joined: Oct 2013
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Again, the OLM is set for lowering warranty costs. It is not the engineers deciding what will make the engine last longer.
I am an engineer. Your trust in engineers is misplaced because management always makes the final decision. Witness the Challenger explosion as proof.
I am an engineer. Your trust in engineers is misplaced because management always makes the final decision. Witness the Challenger explosion as proof.
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
Posts: 34,939
Likes: 12,352
From: NE South Carolina
^^^
Yep, and the Titanic can't sink! Quoting a TikTok whatever is foolish. Read about the OLM then make an informed decision.
Yep, and the Titanic can't sink! Quoting a TikTok whatever is foolish. Read about the OLM then make an informed decision.
Last edited by JerryU; Sep 11, 2024 at 02:34 PM.
Race Director
Joined: Dec 2005
Posts: 11,291
Likes: 953
From: Carlsbad Ca
It's crap oil.
Mobil paid a bunch of $$$ to GM for the endorsement.
GM only wants their engines to last up to 1 day AFTER your factory warranty runs out. Then, they don't give a rat's a$$ what happens. They prefer you replace it with another GM car! How's that for disposability?
Remember when Mobil came out with "Mobil AV-1?" That crap lasted about 2 months, then the FAA forced Mobil to pull it from the market. The problem? It was crappy quality engine oil. (Engines were coated in "gray paint...") Yeah, Mobil, where quality is a 4-letter word.
Retired tribologist, here.