I've had my C7 for about 18 months. I had the oil changed about a year ago and have only put on about 1000 miles in that year. Still, I keep getting messages that I am due for an oil change??? The dealer tells me that the oil must be changed every year regardless of the miles. Is this true, and if so, why? This is my first Vette so I'm still learning. Thanks.

 

Yes it's true. The OLM uses calendar time as one factor.

​​​​​​As to why, people have differing opinions if it's necessary, but in order to keep your warranty good, it requires it.

 

I've dealt with this on my Harley and in my aviation career. Time is a factor, not just mileage.
Here's a quote I found that may help explain:The problem with a vehicle that logs only 3,500 miles in 1 year is that–in most cases–those miles are accumulated mostly with short-distance local driving. That type of driving does not allow the engine and the oil to become hot enough to evaporate the water vapor, and the oil becomes diluted over time.

The process of dilution of the oil, coupled with an engine running on a richer than normal mixture when it is not fully warmed-up, can create the perfect storm for the formation of sludge, internal corrosion, and resulting engine damage.

 

Many thanks for the explanation! I guess it makes sense?

 

Just to dovetail this thread, do most go by the % or mileage? I'm at 41% but based on sticker, I am over the mileage. Yes, I use my dealer for oil changes.

 

Rely on the oil life monitor, not the sticker the dealer put on your windshield.

 

I go by %. Usually at a round 15- 20 % I make call to dealer for appointment. Most of the time it that % for oil change is just around winter storage time.

 

As 2019GSTX says, many with low mileage cars are low mileage because they mostly take short trips. That is very hard on oil due to the oil never getting hot enough to evaporate water that forms from piston blowby. The oil temp (not coolant temp) needs to get into the 170-180 range to purge water and the associated carboxylic acids from the oil. So if your mileage is low because most of your driving is short trips (meaning oil never gets to the 170-180 range), by all means change it at low mileage according to the oil monitor. But if the reason for your low mileage is that you seldom drive it, but when you do drive it, you drive it long enough to get the oil hot, then you can safely go well beyond oil life monitor. Trouble is, if you are still in warranty, it could be a warranty issue. So bottom line, if you are a low mileage driver, two things should be true before you consider going beyond oil life monitor. First, you should be out of warranty so that’s not a potential problem. Second, the reason for low mileage should be infrequent use of the car, but when the car is used, it almost always gets driven far enough to get the oil above 170-180 to evaporate the water and destroy the acids.

 

Yes, it is time to have the oil changed in your Corvette. The oil life monitor uses time as well as mileage to calculate this. My Corvette's oil gets changed every year regardless of the mileage. By the way, that was a good question you asked.

 

Yeah, even if left in the garage for a year. Just do it (preferably yourself) and go on, while knowing your warranty is up to snuff.

 

I generally change my oil by the monitor, which, in my case, means two to three oil changes per year.

 

The GM oil life monitor system (%) uses GM algorithms based on millions of miles of testing and the resulting % is the lesser of 1) actual vehicle operating conditions or 2) 12 months, which is used to calculate when an oil change is needed. This of course assumes you are using the recommended Mobile 1 or equivalent synthetic oil. The sticker, for most higher end vehicles built this century, is based on how often the dealer would like your $

 

All of the above warnings about short trips and oil contamination are true. If you make a short trip, just extend it, which in a C7 should be an easy decision for you to make. E.g., if I want to drive my GS to the gym, which is two miles away, I take a 6-8 mile loop making sure the oil temp reaches at least 175° by the time I get home, which should be warm enough to evaporate most contaminants. The oil does not have to reach the boiling point of water, as the warmer the oil becomes the quicker the water evaporates, and it doesn't magically boil out only at 212° or above. Anyway, in normal city or highway driving my car will not exceed 175° in winter regardless of how long I drive, and I've never seen it higher than 205° even in heavy summer traffic. Oil temp is one of my most closely watched gauges.

 

I change my oil when the oil life percentage indicator is at least down to 5-15%.

MT

 

I've got 5 cars and 1 truck, including my new (to me) 2014 C7 Z51 7MT Stingray.

I don't drive any of my cars, except my MB SUV, which is my daily driver, more than 2-3k miles/year but I routinely change the oil in my vehicles once a year regardless of the mileage. I plan to do the same for the C7.

I will reset the oil change warning notice/light in my vehicles myself if it turns on when it's either not time to do an oil change or I've already had it done and the shop (I normally use Indy shops) failed to reset it.

Found this simple procedure to reset the oil life indicator in a 2015 C7 which should work on any C7 and should stop any further oil change needed warnings to pop up. See: https://oilreset.com/2015-chevrolet-...maining-reset/.

Just remember that the oil life register will need to be reset again when you actually get another oil change.

 

Maybe so, but you're not quantifying your above assertions. Nor is anyone else here. You're just repeating things you've heard and or read, and have made up your mind that; "well, it must be true, since that's what "everyone " says." There's a lot more to it than that assumption. Recently there was a member that directly published/quoted an oil analysis report that pretty much blew your assertions, and others, out of the water on these low mileage models you and others are parroting. In fact, the oil monitor and timelines are basically useless in oil analysis - according to the test results. But that's been known here for years. His analyzing firm's recommendation was for almost a tripling of his oil stats. If you want to argue the results? Have at it. But it pretty much dispelled the standard myths and recommendations that are contained in most of these armchair oil advice threads...

 

Again, Joe, it's not what you or I think, it's a matter of warranty.

If your car is under warranty, follow the OLM, and be prepared to document that. Once it's out of warranty, do whatever the heck you want to do.

 

I do not drive mine enough to have the OLM say it is time for an oil change so mine is based on the once a year factor. The C7 calculates mileage as well as time when it comes to what the oil life percentage is. Since I have a warranty, I follow what the owner's manual says.

 

I'll change it when the G S goes in for the triple flush.

 

My “armchair oil advice” is based on a career in the refining industry, including exposure to actual engine testing and tear downs on various oils. In a sense, your post is correct in that nobody can quantify the exact outcome of some particular oil change strategy. The best you can do is talk about what helps and hurts your odds of a failure, including an explanation of why that particular action helps or hurts. That’s what I tried to do in post #8. But the nature of probability is that a few chain smokers will live to be 100, and a few non-smokers will die young of lung cancer.

For what it’s worth, I’d also point out that used oil analysis is not a reliable way to understand or predict oil-related issues. True, if some particular property is grossly out of line, it can reliably indicate a problem. But in the more usual case where most properties are within normal ranges, with a few being somewhat high or low, it’s essentially useless. That’s because interactions among properties are complex and poorly understood. So beware of taking advice from someone who promotes one or two properties as being the critical ones, or suggests drastic action based on one or two properties being a bit out of normal range. If you choose to doubt that statement, ask yourself the following question. Why would oil companies do very expensive long term engine testing and post-test tear downs to determine oil performance if very cheap used oil analyses were a reliable way of getting the same information?