Tom in Austin

What is everyone's opinion of changing oil once a year if you haven't driven the normal change increment in miles?

Mercedes recommends this, and they put a lot of oil in their cars (my V6 daily driver holds 8.5 qts) similar to Porsche. I personally stick to just mileage, don't see how the oil gets dirtier or the additives degrade when the car isn't being driven ...

Keith Coe

I change it once a year. Yeah, it probably doesn't need it, especially if using synthetic, but I feel that is cheap insurance.

hacker-pschorr

I've read reports that everything oxidizes when exposed, even motor oil, which could degrade it.

How much, how long.....who knows but I agree just sitting in the pan shouldn't hurt it unless we are talking years & years.
I guess it could also depend on the storage conditions. Un-insulated garage going through extreme hot / cold cycles can effect moisture build-up??? Just guessing, but that goes back to the old rule of not starting up the engine unless you will drive long enough to fully heat up the oil to boil off moisture since some amount of condensation will always be present.

I always wonder how often Jay Leno changes the oil in his 150+ cars. You cannot tell me he's doing 150 oil changes a year, could be but I highly doubt it.

FredR

Tom,

I do not drive the 928 a whole lot these days- just a weekend fun type of thing. I use a 20w50 mineral oil [Shell] and have a change policy of 2 years or 5k miles- usually the time factor controls things. Whether that is a sound policy or not remains to be seen. My motor does not see any cold starts and those are probably the biggest engine killer on little used motors. I do not like lots of short stop/start trips - try to avoid those like the plague and leave them to the wife's daily driver

SeanR

I usually recommend once a year but if you've kept your car inside all year round and only put 2k miles on it, wait another year and drive the thing. I put 4k miles on mine last year (usually drive 10k+) and usually change the oil every year before 3rd Coast. Going to wait until next year to do it and send a sample off again to see what Blackstone reports. Important thing is if you are doing short drives and never getting the oil up to temp. If that's the case, then yes, change it.

Wisconsin Joe

I generally do once a year. Motorcycle, 944, 928.
Part of it is habit, part of it is the understanding (maybe correct, maybe not) that there are 'combustion byproducts" that end up in the oil that are not the best thing to leave in there for winter storage (usually ~4 months for me).

With a couple exceptions.

There have been a few years where I only put a few hundred miles on the 944 and didn't bother changing it. It went two years those times, still well short of mileage limits.
The Cayenne runs synthetic and has a mileage interval of 10k. It takes me about 18 months to put that on, so that's how long the interval is. That car gets runs and fully warmed up at least once a week though, no 'long term' sitting.

worf928

I recommend 5-ish-k-miles or two years for synthetic. If you’re driving your otherwise-garaged 928 2 or 3 k-miles per year, there’s little point in throwing away 8.5 quarts of oil every other year. For climate-controlled garage-squatters the oil’s not going to go bad in two years.

If you DIY and it makes you feel good, then great.

polecat702

I have cars that I rarely ever drive. I haven't changed oil in my Packard, Cord, 56 Bel Air, or Aero Coupe, in 5 years. The oil is still clear. I'm more concerned about the coolant.

Leno, is using a waterless coolant, in his Duesenbergs. I'm thinking of going that route too.

Captain_Slow

Mobil 1 20W-50 every two years. Driven less than 1500-2000 miles per year.

Mongo

Every 18 months here with only 500 miles per year.

The Forgotten On

Once a year here with 8K-12K miles on each car every year.

I also use standard 20w50 VR1 dino oil, never had an issue with sludge or buildup of any sort.

Bertrand Daoust

Every two years.

I drive about 5 k km per year.

Royal Purple 20W-50.

OTR18WHEELER

I used to change oil and filter twice a year, but I only average 5K miles per year, so now I change once't a year in the spring. (castrol 20w50 dino)
ps ....read somewhere that the new castrol 20w50 for motorcycles has more zinc.

Adk46

Musings, with no facts, on what might happen to oil over time at room temperature:

Does something good in the oil volatilize in the garage? Does it oxidize? Is there some ingredient that's unstable, like in gasoline? If if can survive hundreds of hours at 200-300F, no, not at room temperature. Can additives precipitate out of solution? Probably not, not in ordinary climates. Similarly, can some of the oil constituents "gel up" if real cold? Maybe, but that has nothing to do with age. There, I think I've covered all the degradation possibilities, except...

Can corrosion occur from combustion products in the oil, or anything else that might build up? I suppose, but is this ever seen? Not the corrosion that may occur when parts that are normally oily become non-oily.*

Can moisture build up? As Hacker suggests, cycling hot and cold might pump moisture into the works. Engine gets cold, draws wet air in, water condenses and is absorbed, sun comes up, air is expelled but the moisture remains.* It might be reasonable to have a long oil change schedule for a heated and air conditioned garage; short for a barn in New England; every month for a car under a shredded blue tarp in the backyard.

* And now for some fact-free heresy: I think it's a tough call between running a car for a short time to get the oil distributed, and the risk of contamination with combustion products (water). There's also the risk during storage of corrosion from stagnant coolant to consider. And issues with stagnant fuel in critical spots. And from seals that may dry out. Most people are not going to run a car at idle in a garage long enough to heat the oil enough to drive off moisture - does your carbon monoxide detector really work? I have this heretical theory that running a car for 30 seconds every month is a good idea - a little contamination in exchange for the circulation of precious natural fluids.

SwayBar

Yes, I agree, this post was pretty much 'fact free'.