How long can you avoid changing full synthetic oil


anything else


Just a note, I said to use the specified oil and follow the OLM, I ever said to extend the interval past that.


Oh my gosh, I’ve got guns I haven’t cleaned in at least ten years. I meant to and its on the list but frankly its been so long since I’ve hunted, I’m not sure what the process is anymore. I’ll put it on the list again.

Not to argue but what we are talking about is a lousy $30-50 a year for an oil change depending on whether you do it yourself or not. So if the book says one year and you extend to two years, all you save is $50 or $4 a month. Even if Keith is right, is it worth it on what a $3-5000 engine? I used to change oil once a month so going more than a year is beyond comprehension to me. I even changed the lawn mower a couple days ago with a little over 20 hours with Mobil 1 in it. Looked a little dirty, and those engines are only $800. For a half hour work and $30, I’m a little more aggressive on oil changes and who cares what the OLM says?


Tu give a completely accurate answer to the OPs question. You can avoid changing the oil until the engine blows up. Your next engine will have different oil.

I recall a. discussion on the show many years ago on the show about how long a car could go without ever changing the oil and someone offered to try it and report back but I don’t remember if it was one of the brothers or a caller and I never heard a follow up. Being an over the road driver without a scheduled run, there was nothing in my life I could do with regularity.


Ya but why is 1 year a magical number? It’s good at 1 year and then at 13 months it’s bad? Mine is at least 16 months old and when I checked it it looked brand new.


Re. moisture in the oil:
It (mostly) doesn’t come from the outside air.
It comes from blowby. Combustion gases slip past the piston rings and enter the crankcase.
Burning hydrocarbon fuel produces primarily water and carbon dioxide.
All piston engines have some blowby.


Before I retired from otr driving I put from 1000 to 1200 miles on my pu a year. I changed oil anywhere from 10 moths to a year.


+1 to @oldtimer_11

Nothing magic about 1 year, but it is an easy thing to remember.

Your post states “avoid changing …oil”

The best and cheapest thing you can do for your car is change the oil. You have a car worth $15K, replacement around $20 to $25k. $50 bucks for an oil change is a cheap way to keep the engine in good shape, not something to be avoided.

By products of combustion include water vapor. Unless the engine and oil get good and hot, the water vapor hangs around,mixes with all the un-burned junk and doing all manner of harm to the engine. Not a major hit each time, but little whacks each short run. These build up over time and wear away at the internals of the engine.


The engine is running, the PVC system is drawing all those combustion by-products, including the moisture created out of the engine and sending through the combustion process again and out the exhaust. The replacement air comes from the outside through the air filter.

When you shut it down, no more combustion by-products.


Does any manufacturer’s oil change recommendation get detailed enough to specify how to maintain a vehicle that is driven 1,500 miles each year and spends consecutive months parked? Like speed limits and oil viscosity everything that is recommended is based on some MEAN-AVERAGE-MODE chart that a commitee of bean counters and corporate gurus reviews and discusses for 15 minutes as they read their email.

My experience with maintaining commercial fleet vehicles including several that I owned included several that exceeded 300,000 miles and synthetic oil was never used but oil change intervals often exceeded 7,500 miles. All were serviced monthly. Some Ford Aerostar vans in a fleet of 7 were accumulating in excess of 11,000 miles in a month and only one engine was replaced before the 300,000 mile mark, low oil pressure was indicated and confirmed. I remain unconvinced that synthetic oil is the be-all and end-all of engine protection. Despite its inherrant qualities it will not preclude regular service. But on late model vehicles it does seem worthwhile to adhere to the API-SN oil recommentation and that will require synthetics.

I wonder, what was the API rating in 1980?




If the oil was getting water in it or mixing with crud wouldn’t it be reflected by the oil getting dark and dirty looking, not be nice and yellow? Also oil and water don’t mix so wouldn’t any water get burned off eventually when the engine is brought up to temperature?


There are a number of technical issues to address, but at the risk of going off topic I have to ask, who cares? Change the oil when the OLM OR the schedule in the owner’s manual says to. There’s nothing to be gained by waiting over a year to change it. You might as well ask “How long can you avoid going to a dental checkup?” or “How long can I avoid having my furnace inspected and serviced?” Sometimes there’s nothing to gain but lots to lose by putting off maintenance.


It is amazing how and oil change question gets everybody going.

I used to have a 2011 CRV and have memorized the manual:)

You have the go by the OLM BUT the manual says no matter what the OLM says, you have to change the oil at least once a year.

I am sure there are a lot of considerations why Honda worded the manual the way they did but with my car I still changed the oil at one year despite the OLM saying I have 60% life left. Even the service writer was not familiar with this wording and was trying to tell me I am too early.


Someone told me that the manual has the “or every year” clause in case people don’t check their oil and it gets low, what do you think of that?


If it is so vital for somebody to avoid spending $4 per month, I think that the overall cost of maintaining a car is probably too much for them.

Or, as our friend, mountainbike, has said–The idea is to extend the life of the engine, not to extend the life of the oil.


I read the chart @keith, and it warned that the SE rated oils would cause sludge build up but there was never a problem with sludge on the high mileage vehicles using that oil back then and they often ran well beyond the recommended mileage for oil changes.

And currently out dated API SM oil is on the shelves of McParts stores and dollar stores in my area. I wonder if it is destroying engines of unwary owners as I post here.


Save a sample and get it analyzed. That way you’ll get a better idea.


Yes, it does, but indirectly. The manufacturer of your car developed the OLM software based on how their engines degrade oil over time. They set up a number of tests where the engine is run and see how the oil degrades. The test is stopped periodically and the oil tested. The engine sensors were monitored to see which ones had an effect on the oil degradation. This isn’t easy and it took a long time to develop the software that is used today. If you don’t trust it, you could just have your oil tested to see if it need some to be changed. But that is about the same cost as changing the oil.


I just don’t understand why this site and the others have so many questions about oil and oil changes. It seems so simple, use the type of oil recommended by the manufacture, change oil by manual service schedule or more often if it makes you feel better and stop listening to people and make your own decisions.