fluid changes
Race Director
Joined: Mar 2007
Posts: 11,468
Likes: 8,641
Yes - the first 7500 mile interval seems to be because of debris (since that is what filters take out). I would say the the 22500 mile filter changes, based on mileage only, are also due to debris. I would say that the 3 year requirement, which does not specify a filter change at the same time, and occurs irrespective of mileage, has something to do with oil degradation, unrelated to debris- since the filter change is not specified. I would also say that the changes based on the OLM, which the manual says is based on a combination of temperature and mileage, has something to with both oil degradation as well as debris. Makes sense to me.
Thread Starter
Racer
Joined: Feb 2017
Posts: 432
Likes: 188
From: powder springs georgia
There was a more in-depth discussion of this on the other forum. The context of the statement was to not skip the DCT canister filter change at 7500 miles. Some people were changing the canister filter very early. The recommendation was to replace the canister filter again at 7500 miles if the canister filter was changed early.
Here is the post that started a long thread. Note that this was prior to GM announcing that they would extend the compensation for the first service to 2 years:
I was at Corvettes at Carlisle today, and there were a couple of presentations by GM personnel that provided some useful information, and cleared up some confusion or misconceptions.
First was a presentation by two people introduced as the program manager for the DCT project and another identified as the Assistant Chief Engineer for the DCT. Both are GM employees, not Tremec. They emphasized the importance of doing the DCT filter change at about 7500 miles to ensure all the break-in wear products are removed. Wear products that continue through those first 7500 miles, no matter how long it takes to get there. The key point was that if you put few miles on your C8, and take advantage of the "free" filter change in the first year with only a few thousand miles on the car, you should change it again at 7500 miles to remove the wear products that accumulate after the early change.
They also emphasized the importance of adding the extra 2 quarts (yes, I know it's actually liters, but even they said quarts) if you "are tracking the car." They said in something like a fast down hill turn, the oil can actually be lifted into the top of the transaxle, causing the oil pick up to suck air. I asked them to define "tracking." Does that include a few lead / follow laps at NCM, or HPDEs, or only if you're near racing speeds?
Their answer was two-fold: First, that they think GM is changing the wording of the recommendation to "tracking or spirited driving," and second, that they would define track use as anytime the car is on a track, even lead-follow laps. I think there's been a general consensus that a few laps at far lower than racing speeds doesn't really need the extra oil. This advice seems to contradict that.
(Don't argue with me - I'm just the messenger.)
They also said a replacement DCT, out of warranty, costs $20,000!
Next was a gentleman named Paul (forgot his last name - sorry) who is the manager who deals with customers or dealers when someone is seeking an accommodation for a problem / repair that is outside the warranty. The bulk of his presentation amounted to "follow the recommended maintenance and the OLMs." He also recommended letting the dealer do the DCT filter change, because the dealer tech will (a) first do the DCT flush procedure to remove as much wear material from the oil as possible. Also, after the filter is replaced, the tech will do a pressure test to ensure there are no leaks. Neither of which can be done at home without the GM software.
I think this eliminates any question about whether the flush is part of the filter change procedure or not.
Here is the post that started a long thread. Note that this was prior to GM announcing that they would extend the compensation for the first service to 2 years:
I was at Corvettes at Carlisle today, and there were a couple of presentations by GM personnel that provided some useful information, and cleared up some confusion or misconceptions.
First was a presentation by two people introduced as the program manager for the DCT project and another identified as the Assistant Chief Engineer for the DCT. Both are GM employees, not Tremec. They emphasized the importance of doing the DCT filter change at about 7500 miles to ensure all the break-in wear products are removed. Wear products that continue through those first 7500 miles, no matter how long it takes to get there. The key point was that if you put few miles on your C8, and take advantage of the "free" filter change in the first year with only a few thousand miles on the car, you should change it again at 7500 miles to remove the wear products that accumulate after the early change.
They also emphasized the importance of adding the extra 2 quarts (yes, I know it's actually liters, but even they said quarts) if you "are tracking the car." They said in something like a fast down hill turn, the oil can actually be lifted into the top of the transaxle, causing the oil pick up to suck air. I asked them to define "tracking." Does that include a few lead / follow laps at NCM, or HPDEs, or only if you're near racing speeds?
Their answer was two-fold: First, that they think GM is changing the wording of the recommendation to "tracking or spirited driving," and second, that they would define track use as anytime the car is on a track, even lead-follow laps. I think there's been a general consensus that a few laps at far lower than racing speeds doesn't really need the extra oil. This advice seems to contradict that.
(Don't argue with me - I'm just the messenger.)
They also said a replacement DCT, out of warranty, costs $20,000!
Next was a gentleman named Paul (forgot his last name - sorry) who is the manager who deals with customers or dealers when someone is seeking an accommodation for a problem / repair that is outside the warranty. The bulk of his presentation amounted to "follow the recommended maintenance and the OLMs." He also recommended letting the dealer do the DCT filter change, because the dealer tech will (a) first do the DCT flush procedure to remove as much wear material from the oil as possible. Also, after the filter is replaced, the tech will do a pressure test to ensure there are no leaks. Neither of which can be done at home without the GM software.
I think this eliminates any question about whether the flush is part of the filter change procedure or not.
Race Director
Joined: Aug 2016
Posts: 12,870
Likes: 10,277
From: Garden Valley CA
You don't want to do the DCT filter change too early or too late. My personal rule of thumb. If you think you are going to have more than 7500 miles on your car at the end of two years, take your free service at the first year mark when the OLM tells you to. Otherwise, pay for the first engine oil and filter change yourself and get your free service in two years.
