Cornell Clark

I change at 40% or once a year.Makes me feel better.

5knives

Get it tested. Anything else is just unsubstantiated speculation, habit, or warm and fuzzy feel-goodiness.

NmtMev

yup... my boosted cars would drop to a 20w in 2k miles... not good. Wear metals always looked great. Test your oil if you really want to know how long it it could last. Whoever has an Oil with 7k miles on it send it on over lets see your wear metal results. That's crazy

CessnaDriver

How about just follow the manual? Crazy talk I know.
Just insane.

0% or once a year.

I never get to zero so once a year.

Bruze

Any summer toys I've ever had got changed before winter. They typically might have anywhere from 1-5k on them.

My C6 is running around 2,500 - 3,000 per season, although the weather has been so horrible this summer I'll probably only put on 1,500-1,800. Oil will get changed anyway before hibernation.

Torchsport

Once it gets below 20%. Usually about 7,000 miles. I don't worry if it takes 2 years get get those 7,000 miles.

Scuba Ghost

Once every 12 months. The DIC normally shows between 50-60%.

flyingbunnys

I change the oil and oil filter on my cars all once annually in the spring. At this point I check all my fluids and top off windshield wiper fluid and replace the wiper blades. I do this regardless of the number of miles driven. Sometimes there will be as much as 8k or 9k miles on the oil other times only about 2k or 3k.

RobLo

Just changed mine, 14 months, 2300 miles, DIC read 79%...I felt guilty going 2 months over the 1 year threshold.

Corvette_Ed

I always hit 10% first, so the oil is changed twice annually at least. Synthetic or no, I value my engine more than I do some oil mogul's opinion.

LDB

I’d say there are three main things to worry about on oil change interval. If you don’t violate any of those three, I see little risk going all the way to zero on the oil life monitor, or even a bit beyond. First is something that doesn’t apply to most people, namely, disabling the PCV system. Some do that to prevent intake valve coking in direct injection engines, while others do it for a variety of reasons generally amounting to thumbing their nose at the feds. They don’t care that they’ve just created a massive increase in pollution from their car, but there is at least a tiny bit of justice in the world, because they don’t realize they’ve also massively increased stress on their oil. That’s because with PCV, the environment in the crankcase is mostly air sucked through by the PCV system, with only a small fraction of piston blowby gas. Without the air movement of PCV, the environment in the crankcase is almost entirely piston blowby gas, and the blowby gas is where all the water vapor, acids, soot, and other bad stuff that degrades the oil comes from.

The second issue is how often you take short trips that don’t get the oil hot. I wouldn’t worry too much about an errand-running trip with a lot of stops. I’m talking about something like a short commute to work, where you often shut down the car and leave it for the day or overnight without having gotten the oil hot. That’s important because exhaust gas (ie, piston blowby) contains a lot of water vapor. Its origin is that gasoline contains about 13% hydrogen atoms which are all converted to water in the combustion process. When the engine is cold, some of that water vapor in the piston blowby gas will condense into liquid water, and that in turn is what allows carboxylic acids to form in the oil. So to prevent acid formation, you need to get the oil hot enough to drive off the liquid water. The oil doesn’t have to be all the way to water’s boiling point of 212F. As long as it’s above 160F or so, that’s hot enough to make the water evaporate during a reasonably short drive.

The third issue is to think about how much VI improver additive your oil is likely to have. I’ve talked about that in many other posts and won’t go through the whole story again, but here are the highlights. That additive is not particularly stable, and if it breaks down, you will lose viscosity on the upper number of your oil. What started out as 0W40 might drop to 0W30, 0W20, etc. Full synthetics have a natural spread of about 25, so if you use 5W30 full synthetic, you are ok on this score. But if you are using a wide spread full synthetic like 0W40, it would degrade to 0W25 if the VI improver degrades. Dino oil has a natural spread of zero, so even 5W30 dino oil has a lot of VI improver. Synthetic blends are in between, so a 5W30 synthetic blend will have some VI improver. The biggest single advantage of a full synthetic is elimination of VI improver for a 25 spread oil, and reduced VI improver for a wide spread oil.

If you violate the first rule by disabling PCV, I’d probably change oil at 70-80% remaining life on the monitor. If you have the short trip problem, it would depend on how frequently you do it, but I might say 40-60% on the oil life monitor. If you don’t use a full synthetic, or if you use a wide spread full synthetic (like 0W40), I’d also say 40-60% on the oil life monitor. If you don’t do any of those, I’d say you’re good to go all the way to zero, even if that’s a bit over a calendar year.

Corvette_Ed

The only reason I use 10% as a guideline is that it gives me time to fit an oil change into my schedule before I hit 0%. I'm too OCD to have the oil change reminder showing on my DIC so I don't wait till it hits 0%.

enventr

Depending on the mileage I put on for the year it's just once a year lately

dmk0210

I change it once a year when I hibernate the car for winter. For me that's about 4000 miles (and about 70% on the computer) since I DD the Vette all summer.

Since the manual indicates changing the oil no less than once a year regardless of the computer reading, this works out well to keep me in the OEM recommended maintenance schedule and keeps the engine in clean oil during the winter when it won't be started again for months.


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ruxvette

I am not disputing your theory(s). However, your "I might say" percentages are, obviously, PFA numbers.
Like others have said, change it when it makes sense to you.

LDB

I guess PFA must be pulled from air, or perhaps from a more colorful three letter “A” word, and to some extent that’s true. On the other hand, there’s also at least some knowledge-based rationale behind it. In the case of PCV, I’m going back to the ancient every 3000 miles limit of the pre-PCV days. Yes, synthetic oil is much more resilient than the oil of long ago. But the acids from lack of PCV are a huge factor, and even with 3000 mile changes back then, engines didn’t last nearly as long as they do today. If you’ve ditched PCV and want to work those trade-offs different from my suggested 70-80%, fine. I’m simply telling you my sense of how it would play out given the background I’ve had over a career in the industry. I admit that I do not have direct tests of that specific question to prove it. The rationale for short trip and VI improver suggestions is also “general experience based”, though in those cases, since the impact is less severe, and VI improver additives are more stable than they used to be, the uncertainty grows. So bottom line, while I sort of concede your point that my suggestions aren’t hard or quantitative, I do think that on fuels and lubes topics, there’s a bit more educated in my educated guesses than most on the forum.

ruxvette

I understand what you are saying. My "education" was running 20k mile oil changes (with oil analysis) in big rigs.
In my personal opinion, the folks that change their oil annually at, say 2000 miles, would be just as well served to change the filter one year and oil the next. Just me.

SladeX

An oil analysis at your next change is an inexpensive thing to do.

It will give you a lot of insight into your driving style (hard on the car, short trip machine, sunday driver etc)

My oil analysis on the vette recommended I go as much as 10k-12k miles on it. I did a change after 1 year and only 6k miles. Mostly highway miles.

I'm at 6k, and have 40% since last change, not a lot of long drives, more 20-30 min drives at most and 11 months which explains the 40%. I will probably still change it prior to winter but only because I plan to do a 6k mile road trip first.

C6 Snowboarder

Approx every 2 years I change my oil. It is good stuff

unclecookie

Many didn't.