Several years ago Consumer Reports did an article on what oils worked best and did a side study on how long to go between oil changes. They ran NYC taxi cabs with identical rebuilt engines and opened the engines after set distances. They found no meaningful difference between oil brand. They also tested whether the interval between changes made a difference. They ran some engines 3,500 miles, some 7,000 miles, and one 12,000 miles. There was little to no difference between the engines when they were opened and the internal wear compared.

I think this is the article I was thinking of. Consumer Reports:Truth Motor Oils- July 1996

I went 10,000 km's on my Z06, the oil monitor came on. It used Mobil 1 synthetic. When my mechanic changed the oil he noted that it was pretty dirty.
Three weeks later I had a low oil pressure warning. Wound up with a broken main bearing. Probably a coincidence but I now change the oil at 5,000 k's.

Twenty five years ago there weren't nearly as many turbo charged cars as you see today. Turbos like relatively clean oil. I wouldn't go more than 10,000 miles on a modern small displacement turbocharged engine. I'd personally go 7,500 miles or less.

I'd be curious to see that same test run today.

That's a good point. A lot of turbos pyrolyze oil. But what if that modern small displacement turbocharged engine had a 3+ gallon oil system?

Point: Lubrication systems have many variable. Higher end cars typically have those variables held to higher standards. If you have a cheapy econobox with a turbo and 4-qt oil system with the cat designed up against the oil pan -cough SAAB cough- then you won't see many of those on the road after just few years - even with 3k oil changes.

But still, many other cars have engines designed for durability / longevity / low maintenance.

Usually I change my oil on all my cars yearly, putting in full synthetic and top quality filters. This year I got lazy with my 2002 W210 Benz and only changed the filter at the year mark.

It takes 7-8 liters of oil and I’ve only put 5,000 miles on it, but it’s been in there since October 2019.

Yes. It’s making me mildly anxious. Haha

Filter changes are typically the least effective thing to do. - notice how tiny they have become on modern cars.

If you want to know what your engine actually needs, do the oil sample analysis.

Taxi service should be low stress as the engine runs all day. I'd worry more if the engine was used for multiple short trips and never got to warm up.

You got me beat but the Boxster will go 4 years w/o an oil change. Reason? Well, not a good one but 4 years = 500 miles for this car. It's my wife's, not mine. If mine it would have been gone a long time ago.

2000 Normal 2.7 with 63,000. It was driven more in the first years. Now I get a few hundred miles and I need to buy a new battery. Drive or not, maintainer or not, they only last as long as they are planned to last. 10 years would be a record for me.

So to the question, the oil has been changed once in 10 years and that was 4 years ago. I use Motul.

But that was 25 years ago. Oil technology has changed a bunch. The synthetic that I use is made from natural gas. While the Fischer - Tropps process used to make this is not new, only recently has it become economically feasible. Additive packages continue to evolve as well.

My wife's Jeep during the busy season for her home building company, it often reaches 10,000 miles so quickly, I can't keep track (every 4 months). The car is rarely home before 6 pm, and she sometimes to forget to tell me.

That year was a 3.4l V8 with a Cosworth block and Yamaha heads.

I have run over 7000 miles at the longest and that was our minivan with the oil monitor telling us it was down to 30%.

Our truck says 7500 and I change it at 6500 or every spring, whichever comes first.

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1996-1999 they had the 3.4 double overhead cam V8. Mine is a 1997 model and it is a V8.

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The earlier were just a Yamaha V6, then the V8 then the turbo V6.

I would bet steady state cruising on the interstate is much easier on turbo charged engine's oil than a track day session.

Yep

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Dang, i do that in a month currently. Commute from Tulsa to Wichita a couple days week. Some days the whole damn state.

14k was my change interval on the 7.3 ford diesel per oil analysis I could have pushed it further, but didn't. That thing needed a lot of oil for one fill, so it was worth checking with analysis. On my current daily drivers it is all 10k change intervals with synthetic oils. The 993 yearly or a little less, if I don't drive it much or have it on the track that year. It has been a long time where i racked up more than 2k / year.

G

Tundra and Outback 10,000 km with Mobile 1 synthetic. Around once a year.
996TT (Mobile 1) and 86 Carrera (Brad Penn) once a year and maybe 5,000 km.

Keeping inventory of the oil/filters is the hard part as I do it myself. Too much crap.

Much of the oil change interval depends on how long you keep your cars. If you swap cars when they get to 80,000 or 100K miles, it does not much matter, 10K oil changes are fine.

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Look at the silicon trace. It would go up, I change the air filter, and it drops to almost none. That is sand and dirt sucked through the air filter.

For my El Camino, it came with a factory 305. It was smoking a lot after 300,000 miles.

This is the cam from that engine. All the lobes were fine, no wear at all. All those miles, and the inside of the engine had almost no sludge after all those miles. The valve guides were really worn, and the rings had wear.

The machine work on a 305 is more than it is worth. I just put in a brand new 350. Not rebuilt, not remanufactured, brand new engine for $1,700. I did it myself over the long Thanksgiving weekend.

I've also read this and when I bought my 2006 Civic Si I did a few early oil changes based on the maintenance minder (MM). I started with the first at 19xx miles, then 50% then around 0% and lastly 1k miles past the 0% MM. All samples were run on Castrol GTX 5W30 - plain old Dino oil. And for those wondering my commute was around 40miles round trip. And I would drive the crap out of the car, pretty much running into VTEC the first 3 gears and very often to the 8k redline. I did notice that the more VTEC the more oil she would drink. The 2014 sample was a normal run with nothing special. The 2018 was the new Castrol GTX UltraClean which had a higher TBN for a normal run. I even had Blackstone test a 2nd time as it was a surprise based on previous samples. So depending on quality of oil, type of engine and driver 5k should be easy on most engines or more. The exception would be for DI cars and especially turbo versions.

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CTopher

I just found out I'll be going 10,000 miles because that's what Toyota recommends. That is unless I decide to change it myself before 10K. I need to find out if that will have any effect on warranty if I change it myself using synthetic oil. 10K just seems nuts.

That question has been asked a lot on the Honda forums. Consensus seems to be that they can't hold it against you as long as you use oil that meets the specs they require of oil.

It's not nuts.

Testing has been done.

Consider that you have been conditioned to believe it's nuts.

I know, "conspiracy theory' right? I mean why would Jiffy-lube to Midas -and every sub-par mechanic in between- suggest you regularly spend more money with them?

It think delaying oil changes will come back to bite you years later at high mileage.
Which will be the next guy.

Sure, you can think that.

And you can think that if a car isn't waxed every week that it will will come back to bite you years later.

Engineering has come a long ways. People who don't understand that will cling to conservative positions of the past - when cars ran fuel rich (which would get past the rings) had crap oil and thermal management that was often sub par. (pyrolization of oils.)

3K mile oil drained from my SC looks more than twice as dirty as 10K mile oil from my Honda Fit.

So what is your theory? 20,000 miles or maybe never?

What does waxing have to do with an engine?

What's your theory on this?

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I just this am checked my Honda Fit for the oil change minder. It says I have 6100 miles since my last change and it is 50% of the way to needing the next change.

I normally do it at 20%. If I wait till it gets to zero..I'll have 12K miles on it.

When I was 16, I had a '65 Chevy with a (not stock) 350 from a junk yard that was probably a '72-74. Changing the oil always resulted in black dirty oil. At one point, I put in a new rear main seal which involved dropping the oil pan. While the oil pan was out, I thoroughly cleaned it. There was a thin layer of gunk in the pan. After that process, oil changes resulted in oil that was barely dirty at all and still mostly transparent.

Presumably, (and I'm not suggesting this) if you could thoroughly clean the bottom of your case, oil tank, engine mounted cooler and front mounted cooler (or loop), your oil would look pretty darn good every 3k miles.

Oils have come a long ways.

Fuels, and fuel metering systems have come a long ways.

Engine materials and manufacturing have come a long ways.

Sounds right. And that has a relatively tiny oil system. (unlike a 911 carrying ~3 gallons)

Even my old 80's VW -I just saw the owners manual- it recommends oil changes at 7500. Those engines go hundreds of thousands of miles with ease, where corrosion is usually the downfall.

What about the lower compression turbo engines everyone is going to?

My old Chevy 305 went 300,000 miles before the valve guides and piston rings were worn out to the point of excessive smoking.

And am sure if I had gone 50K miles on the oil change and then disassembled there would be little wear, but lot of sludge. The wear on engine parts at just 12K would be virtually undetectable even in bad conditions.

I keep my cars long term. The Elky I have had 30 years, the 911 just 26 years. Nether are for sale for any reasonable price. Oil is way cheaper than engine repair. And sludge never gets better, just worse. And sludge will causes lots of problems.

That 300K 305 had regular oil changes. When I pulled it out to put in the new 350, I took the 305 apart. There was almost no sludge at all.

Ok, not a car, but I’ve had a Honda mower for 15 years, I’ve NEVER changed the oil in it.
When I check the level, it’s full, so I just start it and mow

Never my old porsche leaked so much it alwzys had fresh oil.