Used oil analysis is determined to be "not great" for my 2008 C6 Z06. I've been running Mobil 1 5W30 and have participated in three track day events and 2 or 3 autocross events during the 4500 miles on this oil. In accordance with the recommendation on the report, I've checked the intake system and found everything to be clean and intact.

The only work on the engine that has been done is that I proactively removed the heads and replaced them about 10k miles ago with reworked heads from AHP, to prevent the known LS7 valve issue. And I replaced the harmonic balancer 500 hundred miles ago.

Any thoughts about the used oil analysis report?

Due to my plans to use this car primarily as a track day toy, when I changed the oil (and captured the sample for this analysis) I switched to 15W50 Mobil 1. Not sure if this might help the wear metals situation.

 

following

 

I would drain the 15W-50. Unless your car is fully up to temp BEFORE starting your sessions or laps, the 15W will flow less resulting in more wear.

With that out of the way, how many miles are on the car?

When these LS7s start to show metal in oil it's a good indicator of rod coating failure. It is common on LS7s that are ran hard.

The anti friction coating between 2 rods which share a crank journal wear and they end up biting into each other. Easier to catch it before failure.

I'd suggest making sure you don't have coating failure before running it hard.

 

Update: the engine and car have about 53,000 miles. This oil sample had 4500 miles.

 

Thanks for your reply and insight. Could I check for coating failure from underneath the car, by dropping the oil pan?

 

I used to do UOA and Ti was always about 1-2 not 10. With M1 0w-40 mostly.

I think 14w-50 is fine. Who would ever run a track session on cold oil?

I have a 08 as well. I still get small shrooms on the magnet plugs when I change oil. I had my heads redone as well before failure.

I would run a heavy oil like you are doing, and change it at 3K and UOA again. Too many variables on this one to know what is what, but I worry the Ti is sus.

 

viscosity is all about temperature of the oil. a 30°f difference gets you roughthly one class higher (e.g. 30→40). what are your oil temps on the track? with no cooling mods probably too high even for 50 grade oil. even the best oil (which mobil 1 is probably not) starts degrading over 260°f and people change it after every session if they get that high.

 

I disagree on 15w-50 causing increased wear. Increased oil temp? Yes. Slight hp loss? Yes. There's still plenty of flow to cool the bearings. Cold startups could possibly increase wear, as thick oil takes milliseconds longer to reach wherever it needs to go. But it would be nearly immeasurable. I do agree that I wouldn't run it. 0w-40 M1 works great for me....

 

Few thoughts on your data, starting with many too variables to arm chair a definitive source (S) of the errant oil sample readings.

Great move, ditching the Mobil 1 5W-30, GM factory fill, for a different weight/grade oil of which there are so many better options. Not to turn this discussion into an oil thread, Mobil 1 5W-30 is a mass market passenger car "synthetic" but is really just a highly refined conventional Group IIIB (3B) oil with a additive package that classifies it as a USA market "synthetic".....It is NOT a true synthetic. Same for Mobil1 15W-50. The oil you run in these motors matters A LOT!

As others have noted, I would suggest a 0W-40 Supercar/European Formula oils like Castrol Edge, Pennzoil Ultra , Mobil 1 (European Formula ONLY or Supercar) LiquidMoly, and my personal choice, Amsoil Signature Series 0W-40. For Track days, again, my personal choice, would be Mobil 1 Supercar 5W-50. Fun fact-All new C6Z06's for European Delivery only came with Mobil 1 0W-40 European Formula (simply a superior oil to 5W-30, not even close).

I would drop your oil change interval in half, at MOST, with the Autocross and Track days you list. Personally, I would not even go 2,000 miles before changing the oil. Frequent oil change intervals are CHEAP insurance versus an LS7 motor problem.

Lastly, as noted previously, the bottom end bearings and rod bearings, could be a potential issue BUT the heads were "fixed" 10,000 miles ago and can and do fail post rebuilds. Have you checked the heads and valves for excess movement since the install? Again, personally, I would not fix OEM LS7 heads at this point with what I know about the head issues but would opt for a completely NEW aftermarket heads from anyone of the reputable vendors on the forum-there are several.

 

Have you looked into the "Driven GPI" oil?

 

https://www.corvetteforum.com/forums...0-vs-0w40.html

TLDR, the factory fill 5W-30 is 28% thinner at cold start than 0W-40. 5W-30 also flows better hot, however 0W-40 is 32% thicker when hot (>212 degrees).

And since the vast majority of owners don't actually drive their cars since it's like a museum piece to them, the extra wear on cold stars (and the extra zinc that can contribute to catalytic converter failure especially in my case! (ZR1)) is measurable.

5W-30 works for me for a purely street driven car. Plus a 12 quart box is $60. Add in a measurement funnel thing and good to go.

For track use, Tadge in the past said to use 15W-50. Period. INB4 this becomes another oil thread.



Bottomline, years back Castrol successfully lobbied to change the definition of synthetic oil. Absolutely nothing you can buy on the shelf today is “100% synthetic” in that way, even 0W-40. The expensive boutique oils like Amsoil still claim to be 100%. Does it matter much if you’re changing it every 3-5k? Probably not. YMMW.

 

Question for you.
When she's hot does she drag to start like if the battery was dying?

https://americanheritageperformance.com/

 

what would that indicate....curious?

 

CRN coating failure on the stock GM LS7 titanium rods.
In short the rods swell with the heat and they rub together and eventually wear down the CRN coating. Once the coating is gone its raw ti on raw ti and you have massive amounts of friction. So the starter will act like its got a low battery but what is actually happening is the starter is fighting mechanical friction of the rods actually rubbing together.

https://americanheritageperformance.com/

 

Appreciate the clarification.

 

No, I did not notice any change. It fires right up hot or cold.

 

I agree about changing your oil more often when lapping. Especially during the summer. If the oil starts approaching 300F (somewhere around 312F is the max limit) I'd change it after getting back home. But if you aren't using much oil on the track then it means you aren't flogging it hard enough. 3 MPG and 1QT of oil is a good track day in a Corvette.

 

84ppm is alot of Iron. When my Dodge 5.7 HemI was quite literally eating a cam lobe for dinner I got a 38ppm.


Running oil that long with that much hard use is a huge red flag for me. I run 4K OCI just normal driving. But having hard used oil in that long and abuse it some one is just bad juju IMO>

 

I only checked the oil temperature once and wasn’t monitoring it, but when I did check it was 245 at the most recent track day, running with the 15W-50 oil. This was during my cooldown lap, right after running hard for about 15 minutes. Ambient temperature was around 80-85 degrees F.

 

So, your iron is elevated. (Same with Ti.)

Let's take iron, first. What would/could be the origin of the iron?
1. Crank
2. Cam
3. valve stems
4. push rods
5. trunnions
6. other iron inside the block. (Springs and things.)

So, it's very difficult to guess which part is wearing, but it's safe to say that whatever part is, it's likely heat-treated so subsequent wear will only accelerate due to the alloy underneath the case, is softer. Cams are a prime example of this. Hard on the surface, but .025" down and they are butter.
The best way to diagnose is a complete engine teardown.

I'm going to skip the Ti, as we all know the components in the LS7 that are Ti. But, they ARE elevated.

So, we have values that are elevated. Right now, it's just something to watch. I'd pull another sample at the 3000 mile interval. This will tell us if wear is accelerating, or not. In fact, I'd pull samples every 3000 miles until you sell the car. In doing so, you create a "trend." These trends should be the most useful information you can have. (I've had as many as 20 samples from the same unit. Sometimes things were elevated, then they calmed down. )In fact, once it was silica, and Blackstone called me and told me my air cleaner was passing silica. SAND. I didn't even know that my filter element had folded over, on the edge during insertion, leaving a path for unfiltered air to grind my engine into a lump.

Gotta whole bunch more, but gotta go walk the dogs...