Oil changes based on time or miles?

[PeteKz]

Inmates: This is a recent article about Blackstone Labs' tests of oil based on age and number of miles of use. The bottom line is that modern motor oils do not deteriorate over time, but with cumulative use. This article and conclusions correspond to the results of my oil testing on several of my vehicles, one of which I drive regularly, and the others which I drive irregularly.

Many of you like to change your oil frequently based on time (6 months to a year), but the evidence indicates that is not necessary. Throwing away more used motor oil isn't good for the environment either.

Oil analysis costs about $30 at Blackstone Labs, so that's small compared to an unnecessary oil and filter change. If you really want to know what's happening inside your engine, it is the best test you can do. Given that most of our cars hold between 10 and 12 quarts of oil, they have a lot more oil than the average v8 engine with a 5-6 quart sump, so the oil should last roughly twice as long.

www.thedrive.com
Motor Oil Age Doesn’t Matter as Much as Mileage: Study
An oil testing laboratory has found that the conventional wisdom of six-month oil changes might be a waste of your money.
www.thedrive.com www.thedrive.com

[fizeus]

I regularly change oil not because it deteriorate but to avoid carbon deposits building up in the engine. any way i agree that if a vehicle is irregularly driven oil properties do not change so much with time

[Ian Comerford]

I usually change mine every 3-4k miles, which is once or twice a year depending. I use oil analysis to keep an eye on engine condition so that I can understand if it is over fuelling or similar, it’s really useful. I don’t use oil health analysis to drive higher mileage changes as I still consider an oil change as cheap maintenance.

[Starless]

Thanks for the info. We have a 2016 Subaru Crosstrek that we rarely drive since my wife has been working from home since 2020. It has aprox. 44,000 miles. I used to change the oil every six months or at @ 6000 miles. Now we put maybe 3000 miles on it yearly, and 1000 of those miles are for a vacation trip we take twice a year. So basically, other than the trips we're putting 1000 miles on it yearly. We do try and make sure that when we do drive it we drive it long enough to make sure the oils gets good and hot. I've been doing yearly oil changes and had been wondering if I should do them every six months instead. From this report I guess I'll keep on the yearly oil changes. Thanks again for the report.

[shoooo32]

I don't think modern cars are a direct comparison based their ability to run much leaner than, let's say, a 911 running MFI or carbs. I was always under the understanding that the gasoline collected in the oil would hurt the bearings if left for long periods of time. That's why I change the oil in fall before storing them. Admittedly, I have no evidence to back up my actions, but I've done okay in life following the advice of oldtimers

[PCA7GGR]

I had '11 Benz and '04 GT3 that I put approx. 4K miles a yr on using Mobil1 0W/40. I contacted Mobil regarding oil changes and they recommended doing it annually. Their reason was due to the natural degradation that occurs in engine oil once exposed to moisture and other contaminants.

I do my own changes so the cost is minimal (5qt jugs for $35 at WallyMao plus an oil filter).

[Showdown]

The nice thing about a 911 is that because it burns an absurd amount of oil, you’re constantly adding fresh oil to the car… basically a continuous oil change.

/sarcasm

[pavegeno]

Originally Posted by Showdown

The nice thing about a 911 is that because it burns an absurd amount of oil, you’re constantly adding fresh oil to the car… basically a continuous oil change.

/sarcasm

I use Porsche 10W-60 oil in my 88 3.2 NA and change every 5K miles or one year, which usually occurs at the same time. I never add oil in-between and never have over the course of the last 19 years and 108K miles I have put on the car. It now has 176K miles and going strong (fingers crossed).

I use FCP Euro so the oil, filter, drain plugs, and crush rings cost me nothing except shipping back the old stuff ($30 dollars).

[OK-944]

944 ('87NA) owner here, engine rebuild I'd completed in Spring of 2021...chiming in to say that my car loves the Porsche Classic 10W/50 - the level of which has remained absolutely unmoved at the top line of the oil stick, coming up on one year (about 3,500 miles of year round driving) since I'd last changed this oil.

But I do have a question: Part of my "theory" about the Spring oil change to begin a one-year cycle is that by the time Winter rolls around, the oil itself will have "thinned out" just a tad - lowering its effective (10W/50) rating so that cold (northern Vermont Winter) starts are a bit easier than if this
oil were fresh. Does this make sense...or might I have it backwards?

[GH85Carrera]

One big issue for infrequently used cars is the oil can accumulate water from condensation, just the the gas tank. If you drive it far enough too get the engine up to full operating temp, the water will evaporate. If you have opened an oil fill cap and see a milkshake goo on the cap, you have moisture issues. The 911 being air cooled takes a long time to get warm in the cold winter months.

I drive my 911 5,000 miles or more each year, and I do 8 to 10 autocrosses, and a track day each year. I have no issue changing oil after just 5,000 miles. My daily driver, 1986 El Camino went 300,000 miles on the original 305, before it was simply worn out at the valve guides and rings and was smoking. I swapped in a brand new 350, and took apart the old 305 just see if the inside of the engine was clear of sludge.

It was remarkably clean and had no sludge at all. I changed the oil at 3,000 miles. For my 911, I usually change it once in the spring, and that is usually 5 to 6 thousand miles.

[Bill Douglas]

I do oil changes more often than needed on the cars and motorbikes. Whether it's needed or not I find it good for the soul. I'm not so good about sparkplugs and aircleaners though.

[OldSpool87]

I change mine yearly (very low miles per year) to have the documentation if I ever sell b/c you never know what’s important to the next guy/gal.