Oil viscosity isn't the only reason you warm an engine up before revving it hard, especially fairly high compression engines that can reach very high rpm. Different metals expand at different rates based on temperature, and internal engine tolerances are generally closest to optimum at a specifically designed temperature. Temperature also effects material strength/elasticity of metals - some more than others. A mass produced, loose tolerance engine that revs to 4500 rpm has less potential for problems than an 8600 rpm precision piece of machinery that is built with tight tolerances to extract as much power as possible. I wouldn't even think of revving one of my expensive track motors until oil temps reached 180* or so and had been there long enough for things to stabilize. Low operating temperatures may or may not have been a factor in the failures we are seeing, but until GM (or others) release the data on failure modes/causes, we are all guessing.

 

GM won't release the failure modes.

 

The big assumption here is that the failures occurred because of oil temperatures were low for high rpm usage.
The other big assumption is that on the LT6 reported oil temps (by the DIC) is comparable to traditionally reported temps on other engines. Do we know if the LT6 is 'overcooled'? Has anyone measured water and oil temps independently from the DIC?

 

Wait until one of the resale cars with no warranty has a problem - out of GMs hands.

 

Agreed. Especially with this high reving engine.
If friction/wear is the issue, I would add some zddp to my oil. I would do that anyway and take my chances especially when warranty has expired. Jmho.

 

Awesome track times. I ran my 458 Challenge car last week and although I’m relatively new to tracking and the car is new to me, managed a 2:05. Garmin Catalyst is good at showing areas where I can improve.

A friend running a GT3 told me anything less than a 2:03 is hard work. These are beasts on track, though a guy in a


Lambo was sub 2 all day.


Kudos for tracking the Z06. Looks like great combination of power and handling for the high speed tracks.

 

A lot of people who drove the car in cold weather, including myself, had oil temps stay below 150* for extended periods when driving on the highway or roads with infrequent stops. On the drive back from MM, for one segment I drove for almost 2 hours and was below 140* for almost the entire time. After the uproar here and on the other forum, the corvette team was contacted and the response was the oil temp is not measured in the block as it is in other cars.

On my stingray, oil temp and coolant temps rose at almost the same rate during warm-up. Except in very cold temps, coolant would get to 170* or so and oil would get to 140* and the tach would show full redline (6500 rpm) available. On the Z06, I've seen coolant get to 170* while the oil temp is as low as 110*. At this point, the tach displays full redline capability, even though I won't get on it at this point.

So the question is does the oil warm-up before it passes into the valvetrain and the low reported temp doesn't matter, or did the engineers reuse the stingray tach algorithm for moving to full redline and failed to recalibrate it for the Z06. I find it hard to believe that during cold weather testing that no one noticed the tach provided full redline with an oil temp below 120* and did not investigate this.

 

VIR is my home track... all depends on your tires. For the average 400-600 horse sportscar, anything sub 2:10 is a decent lap on a street tires. On track/race tires anything sub 2:00 is a quality lap. Past that there are too many variables. FWIW the C5 I used to race at 385 rwhp held a class track record with a high 1:58 for a time. (2014). Now the same class record is a 1:56.xx.

That said, GM took the C7 ZR1 in OEM trim out and ran a freaking 1:51!!!! years later I'm still in love with this video. Don't get tricked into the silly grand course videos... This is the real deal on Full course.

 

I agree. However this part of the discussion and my reply was about OIL temperatures, not engine temperatures or engine coolant temperatures.
More directly the discussion was about oil temperatures that weren't rising above 120-140* and if this could be related to premature engine failures because the oil wasn't warm enough. The discussion was also about the new location of the oil temp sensor having an effect on the perception of when the oil temp was actually warm because the "normal temps" seen at the new location will always be lower.

I hope we all know not to rev ANY ICE engine to max rpm until its warm! LOL.

 

At how many events did GM reps rev the crap out of cold Z06s. If they did it, it must be ok

 

I live in the Twin Cities and only have about 100 miles on my Z06 at this point. I put about 40 mostly highway miles on it on Saturday afternoon with air temps around 40 degrees or so. Warming up, water temperature increased much more quickly than oil temperature. On warm up, water temp increased to ~172 degrees and then it seemed like thermostat opened and water temp then dropped down to low 150s and maintained that level. It took a long time for oil temps to increase to ~130 degrees, and maintained that temperature except when stopped at stop light where oil temperature would increase to ~150 degrees. As soon as I started moving, oil temperature would drop right back down to low 130s. Seems like radiators are doing their job very efficiently.

I’m interested to see how operating temps change as air temperatures increase, and also very interested to hear how Chevrolet engineers respond to questions regarding operating temperatures. It is a little unsettling when driving with oil and water temps that low - much different than what I’m accustomed to with my LT4 and LS7.

 

LT4 runs hot = we all complain
LT6 runs cold = we all complain

GM engineers and marketing

 

The LS7 oil ran 150* and under in normal cruising on a 70* day until they installed the water/oil cooler from the ZR1. Even our 4-cylinder Forester runs ~200* oil in normal driving. The new 5W-60 M1 formulated for the LT6 was probably not optimized for oil temps at 140-150* on a regular basis, but I am glad that it shouldn't have to run 280*+ like the LS7 and LT4 did on the track.

 

The other engineering issue one has to keep in mind on engines that rev this high, is frictional heat at the rpms needed to produce power. These engines shed enormous heat due to friction at high revs, so the oil cooling system has to keep up. Boosted engines also generate enormous excess heat at high power settings, and you have some of the same problem. An oil cooling system that can keep up with temps at high power levels is going to overcool the oil at lower operating and ambient temps. The ideal solution would be flapper doors to control the amount of air reaching the heat exchanger to keep it within a certain range or, in the case of air to water/coolant, variable speed coolant pumps. This of course adds significant complexity to the system, as well as more failure points and parts. GM tends to want to keep things simple.

As a point of reference, my 458 oil temps run very cool on the street... about 165-175F on a 75F day. And if I drive the car like a Camry, they will never go above 165F, even on a warm day. Now if I start getting into the throttle, they will pretty quickly move into the 185-205F range. It never goes much higher than that, however, unlike my vettes which will quickly get north of 250F... my 16 Z in particular.

I will never forget one day I was hammering it at Fontana with my C6 track car and I looked down and was shocked to see my oil temps right around 300F. My pressure had cratered to 35psi in the 3-6K rpm. The engine seemed to be running fine, but I immediately pulled off the track assuming engine failure was imminent. No damage was done that day but I could not believe how the oil basically turned to water at 300.

So I'd say the C8 Z oil temps people are observing are the way the car was intended to behave. Too cool is better than too hot when it comes to the oil shear layer.

 

@TTRotary Seems like a thermostat in the oil cooler line would also work. Have it open starting at 160* or 180* and be fully 10* to 20* later. Used one many years ago, but it wasn't in a car that was tracked on a road course.

 

Can just drive off right away after starting it up? How about let it idle/run for half to 1 min before driving off?

 

Thread on FB group about a tick that's not the DI system... multiple commentors have it and GM engineering is aware.

 

On all my other cars I start them, buckle my seatbelt, put them in gear and drive off. With the C8Z in the garage, I start it up buckle up, wait the ~30 seconds for the exhaust to quiet and then open the garage door and drive off. (the exhaust is pointed right at our neighbors' bedroom) When out in the open I just buckle up and drive off. I don't get on the throttle heavy until the car is fully warmed up. I don't know of a manufacturer that prefers a long idle warmup to cold starting the car and driving off modestly within 1 minute of startup. Chevy does not have any special recommended warmup procedures for the LT6 engine in our C8 Z06s.

Race Engines are different.

 

Let's assume GM acknowledges that there is something wrong in the valve train and it's out of spec. The next hurdle would be GM claiming it was caused by abuse. How do you know your engine didn't have a few cold revs or was abused? From the time the engine left its initial dyno until you got the keys to your Z06? Has happened before. Or when you valet park or have your car serviced? Time to park that thing and cash in after 6 months.

 

Video on FB group showing a prominent ticking that isn’t injector.

https://www.facebook.com/groups/981031309421592/permalink/1356809661843753/?mibextid=ykz3hl