Increased oil change intervals


I run synthetic oil in everything, no matter if it is required or not. Someone above mentioned a mower coming back to life after switching to synthetic and I experienced much the same with a couple riding mowers. Both came to me used and had essentially the same Kohler Command commercial 16 hp single cylinder engine with hydraulic lifters. Both had been neglected and used a considerable amount of oil and smoked, especially when heavily loaded.

I switched to Rotella T6 5W40 based on some suggestions and the smoking stopped within a few hours. The lifter ticking also went away and performance increased dramatically. The new oil looked dirty quite quickly so I changed the oil and filter. After that, I run a whole season and never need to add oil. The oil also stays clean quite a long time and doesn’t look dirty when I change it once per year.

I run these mowers hard and load them down. I even have a wire to bypass the governor and pull the throttle wide open when mowing what are basically hay fields with these things as the governor doesn’t seem to be able to handle this. They are run like this hours on end without a rest and don’t seem to skip a beat. I have only had one issue doing this. A deck belt broke while I was mowing very tall grass and the engine was suddenly unloaded and revved far beyond spec before I could stop it. There was a pop and the engine shut down with a bunch of clatter. I figured it had thrown a rod but I pulled the plug and could see the piston moving up and down. I then pulled the valve cover and found bent pushrods laying there. I bought new pushrods and installed them. You wouldn’t know anything ever happened and the engine is still running great.


Agree! You test the oil for each type of driving cycle. No need to test for every oil change.

I also did this years ago and found for my mixed driving style that the manufacturer’s interval was about right. But driving at legal speeds across North America on a holiday trip allows you to go at least twice as long without excessive contamination.

Taxi operators normal laugh at the manufacturer’s statement that taxi service is heavy duty and requires the very short interval. Taxis put on a lot of miles with few cold starts and with good oils can run at least twice the normal interval without excessive contamination or breakdown. Many go much longer and compare the cost of oil changes and lost time with the cost of engine repairs. This type of analysis does not work for the average car owner, though, since too few miles are driven in any one year…

Using the 5000 mile interval my oil had only 65 parts per million (ppm) of total metal wear, which is minimal. All other factors were within safe range. EXXON condemns oil at 200 PPM.


No, I do not test the transmission fluid. I drop several quarts and add back every maybe 20,000 miles. the old car transmission works perfectly at 222,000 miles. Fluid looks brand new, too.

I got this idea when the car was fairly new, from the Brothers on this URL.

I asked the local Toyota dealer service writer, a friend of my son-in-law, how long transmissions lasted in Siennas. He said he could not remember a failure, so this is my solution.

If he had said something different, yes, I would probably be testing the transmission, too.


That was pretty much the life of my 2002 Sienna. driving at legal speeds across North America. And, yes, the oil testing showed good oil probably up to at least 11,000 miles estimated, around twice what others change at.

I do remember an article many years ago, by Tom McCahill. He said taxi companies in his day did testing. First, change oil, by memory at 1,000 miles. Boy that seems primitive now, doesn’t it?

And, the motors lasted, again by memory, around 100,000 miles. Then, change at gradually increasing mileage, and motors lasted slightly less distance. The final test was don’t change oil, just add when needed, and I can’t remember if the motors went 20,000 or 40,000 miles with no changes at all.

Many people here report, as I can, the motors and transmissions simply outlast the car, due to general wear and rust issues.

Thanks for the ppm data. What a great board!


I change my synthetic oil somewhere between 15K and 20K. Depends on when I have time. I frequently sample the used oil and send it for analysis and it is always still within spec. Who knows how long I could go. I suspect that 25K+ would not be unrealistic as long as it stays clean and does not get hot.


I have a learning question. What year is your car? Is it possible newer ones are somehow designed to run cleaner? This is a curiosity question, and may be a really stupid question, not the first one I have ever asked on this board. :smiley:


My old car was a 05 camry running on propane. It went to 265K miles. My current car is a 08 Yaris that has 260K miles on it. The key is clean oil that does not get too hot.

If you think about your automatic transmission. The oil intervals are generally 30K at minimum and many new cars have what they call lifetime oil that is never suppose to be changed. Transmission does not get as many contaminates because it is a closed loop system. The oil in your engine is also closed loop however there are particulates that are introduced through the combustion process. Most of the contamination comes from the carbon deposits left from burning the gasoline. Propane is much cleaner burning and after 20K miles the oil would be almost as clean as when I originally put it in. Newer computer controlled fuel injections have helped maximize the combustion which helps keep your oil clean compared to the older carburetor cars.

New oil technology and refinement has also came a long way in the past several decades so that also helps add life to the engine oil. There is also probably something that could be said about engine designs and machining that has reduced wear and heat buildup in the engines that also will destroy the oil.


Another educational and informative posting! What a great thread! Thanks.

But, all these details which support increased oil life also explain why it might be important to test your oil. Most of us are sort of still stuck back in the days of 5,000 mile oil changes, without any supporting evidence, and we may need a personal lesson on modern oil life reality.

Or, of course, not, if that is what you find out.


I don’t have much to add and will continue to change my oil at 5000, but one thing to consider is how often anyone really has major engine or even trans failures anymore. Outside of my diesel which is an unfair comparison, I’ve never had any internal engine problems except a timing chain. And that’s with anywhere from 2-500,000 miles on them. So even if engines are abused somewhat with extended oil changes, they’ll probably still give reasonable service. It’s all the other stuff that can start to go wrong with cars that causes the problems I think, but engines and transmissions are pretty dependable.

Not always I know. A former co-worker had to have a new engine in his Hyundai at 90K so a $10,000 failure is nothing to sneeze at, but still there are lots of other maintenance and repair issues to worry about than oil changes.


I have been mixing Web with irrigation. I live in technically a desert area, though not the sand type. Yes, cactus flourishes.

And, a cousin and I bought over half a kilometer of 2 inch hose to run water around the hillside from a big spring. Today is our water day.

But, while doing that, I had some weird ideas

Where is our data?

I think we are mostly steering out the back window. My 11,000 mile oil, by test, was in a car produced in 2001. Motors have changed dramatically in those 16 years. Horsepower and mileage for the same size motor seem to be much improved.

Propane on a 9 year old car noted that with clean burning propane, his oil was almost as clean as new with 20K on it. Though I am not sure that being clean looking means the additives are still good.

I have read that in Europe they change oil at maybe 15,000 or more. And, someone here said they got a notice from Toyota that the 5,000 mile recommendation was summarily changed to 10,000.

What if they are correct, and we are “steering out the back window”? What if the improved mileage and horsepower also means much cleaner burning motors? And, we are stuck back in history?

Where is our data?

Usually, when we have these discussions, there will be at least one person who says haughtily, “If you really care for your car, you will (fill in the blank).” Usually involving very short oil changes or whatever, with no data to support it.

My view is, if you really care for your car, you will find out what YOUR car needs and provide that, with perhaps a modest buffer. If your car needs oil changes at 4,000 miles, that is what you will do. If your car only needs oil changes at 20,000 miles, then that is what you will do. No more; no less.

My car is a 2009, so at my age, I will probably never have a newer one. I remember doing the oil test on my 2002, which is now an ancient vehicle as great as it runs, and found out I could easily go 11,000 miles on Mobil-1 EP oil. A lot of people were sure that meant I didn’t really care for my car. Nonsense. It only needed to be changed at 11,000 and doing it at 8,000 was plenty of buffer.

If you REALLY care for your car, you would get the oil tested at the time you have chosen for oil changes, and see what your car really needs. Until we get that data, we are just guessing that motors have not changed in decades.

The summary change from 5,000 to 10,000 indicates something dramatic has happened. Clearly, the 5,000 mile rule was a wild guess, and it has been updated with more experience.


I change the oil and filters in all my vehicles at 5,000 miles with dino oil. Because none of my vehicles are operated under conditions that require synthetic oil.

Been doing it for 50 years.

Don’t need to pay for any oil testing.

Just inspect the drained oil to see if there’s anything amiss.

Also, my vehicles don’t go the scrap yard because the engines are worn out. They go to the scrap yard because the bodies are rusted out.



ONE oil test when you buy your car will NOT be a good indicator for oil change interval 200k miles later. To be accurate you’ll need multiple oil test for the next 200k or 300k miles.

To me, that’s just cost prohibitive.

5k oil changes work to keep vehicles running well for 300k+ miles.

MB had a great line some years ago which I’ve used…are you trying to get the most out of your oil, or the most out of your engine? Oil changes are cheap…engine rebuilds are expensive.


When I was working as a faculty member at a university, I changed the oil after spring commencement and after fall commencement. I had to rent a cap and gown to be in the commencement processional, so I just wore it on home and did the oil change before I turned the cap and gown back in. I figured for the amount we were charged to rent the academic regalia I might as well get as much use out of it as I could.


Fifty years ago, in 1967, the oil change interval was about 3000 miles, 2000 miles on some cars. My 1966 Malibu had a 30 day oil change interval for below freezing and 60 days for temperatures above freezing.

The oil spec was service MS, or GM spec 4745-M. Grade was 10W30 for above freezing and 5W20 for below freezing . A 5W30 had nor been developed yet.

The new API classifications had not even been developed yet!

In those days a 5000 mile change interval was very long and applied only for summer driving


@Docnick. Sixty years ago, a 2000 mile oil change was common. My Dad had the oil changed every 2000 miles back then and had a chassis lube every 1000 miles.
The owner’s manual in my 1965 Rambler Classic called for an oil and filter change every 4000 miles which at the time seemed to be a long mileage interval. I think the time interval was 6 months.


My opinion on this topic is different because my view is different. There are three groups who read Cartalk, not just one.

First, those of us who come to find out information on our own cars, and how to care for them, and what to do if bad things happen.

I really don’t care what this group does on oil changes. It’s your car; your money; your business. If you want to change oil every 12 miles, I don’t give a hoot.

However, there are two other groups who use Cartalk.

Second group is the general public, who at times view Cartalk as a good source of accurate and up to date information on cars. If Cartalk forums continues to use the same old theories on oil changes, IF oil life is indeed changing, this forum is going to be a laughingstock.

We have no idea how many people read our postings. It is not uncommon to have 5 or 10 readers for every person who posts. It may be proprietary data, but our moderator probably knows.

I moderate one low traffic board, on certain social issues important to men. We may not get one posting per month, and it will be mine. But, eventually some of our postings accumulate 100 or more views, since one can read without logging in, except the Members Only thread.

I would expect a high traffic board like Cartalk to have even more “lurkers”, as they are called. People who come to research specific information they need, and of course usually referred by Google or another search engine.

We still get reports of oil change places telling their customers to bring their cars back after only 3,000 miles, which is really lame.

And, lame is what this board will be if we are unwilling to supply updated information on oil life, if indeed it is changing.

But, wait, I said two more groups. We do have professional mechanics here. A couple very good ones. If all mechanics were as good as our best ones, mechanics would not generally be viewed by the public as incompetent thieves. Like it or not, alas, that is the general view by the public of mechanics. Which is why this board has Mechanix Files to publicize the best mechanics.

As a pro, if there is a dramatic change in any aspect of car maintenance and service, it behooves you to know it.

Triedaq above said he got a letter from Toyota telling him he could extend Sienna oil changes to 10,000 miles. That is the manufacturer recommendation, not my personal opinion. In spite of sometimes sarcastic remarks by the usual suspects, Toyota is conservative on maintenance recommendations.

That to me is a major indication that something has changed dramatically. My theory which I have stated above is that cleaner burning motors extend oil life. Theories are made to be proven or disproved. I have an older Sienna, and will most likely never buy a newer one, being 75 years old.

There are two ways to find out. If someone knows how to communicate with an oil lab, ask them the question if newer cleaner burning motors can reasonably have extended oil changes. There may be legal or political reasons not to answer correctly, of course.

The other way is for someone, anyone, with a 2017 car, such as Sienna, to wait until their chosen oil life cycle, and when changing oil, send in a sample and then report the results. As I did many years ago, when I learned my Sienna with my driving cycle could go over 10,000 miles with Mobil-1 EP, totally contrary to consensus on this board.

My 2009 Mexican Sienna is not a good sample. It was driven 50.000 miles in our state capitol which produces conditions much like Brooklyn, NYC in the late 60’s when I last drove there. The first oil change dirtied very fast. The second one was much cleaner. If it cleans up, maybe I can use it, but not yet. So, I have no way to obtain data, and the 2009 is 8 years old as well, thus not valid data.

I say again, I don’t care what you do, but that is my viewpoint. But, it would be a public service if this board were able to supply valid information.


This is why I don’t use synthetic oil.



And how would someone know they are reading valid facts on a forum with screen names. Forums are just a way to see opinions. Just like the person who just recently found out that the vehicle tire pressures are on a door sticker and the number on the tire that says maximum pressure is not what you inflate to.


If I still did my own oil changes, I would be tempted to purchase 0W-20 full synthetic at my local Rural King store under the RK brand label for $2.79 a quart. It meets the specifications for my Sienna. However, I no longer do my own oil changes for two reasons: 1) at my age I don’t feel like putting the vehicle up on ramps and changing the.oil; 2) it costs too much to rent a.commencement cap and gown to have something to wear to change oil (see my earlier post). I now depend on my Toyota dealership to do the right thing. Besides, any time I bring the car in for service, they give it a wash job. The independent shop where I used to trade put 5W -20 in the Uplander I used to own instead of 5W-30. It was wintertime, so I figured it wouldn’t hurt anything. I did insist that the correct oil be used at the next change. I kept my eye on the oil level, but I never needed to add oil. On my previous Sienna, they put in 5W-20 instead of 0W-20. Since it was summertime, I didn’t worry about it since it was full synthetic oil. However, I never went back for an oil change and have since stopped using the shop.
I do miss the days when I did my own vehicle maintenance. The last 10 years of my employment as a.faculry member at a.state university, more pressure was put on us to publish. However, less emphasis was put on quality teaching. I still demanded a lot from my students and did all my own grading so I knew whether the students were.understanding the concepts. I also had one of the best publication records in the department to show up some of the younger and very arrogant faculty. For that reason, some.of technology has gotten ahead of me. I didn’t have time to do my own automobile maintenance. Now that I am retired,.I have become.too lazy to do the work.


Yes, I remember getting 4 oil and filter changes per year, about every 3000 miles. Cars had carburetors which caused much oil dilution with raw fuel. Today’s oils are light years better that the MS (Motor Severe) classification of the mid sixties.