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Oil Change Intervals Objectively

Ron Texas

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I have an ICE car which is driven about 2000 miles per year. Use is split between short and long trips in a warm climate. It came with synthetic blend oil but now runs full synthetic. Everything I could find says never go more than a year between oil changes without regard to mileage. However, I have been unable to find any objective data showing how much slipperiness the oil loses simply due to the passage of time. Is such objective information available or is the one-year interval something left over from the days before synthetic oil, a manufacturer's CYA or an old wives' tale?
 

Rottmannash

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Not sure but wondered the same thing. I always use full synthetic in my cars and motorcycle but the oil change folks always write down a 3000 mile interval which makes me crazy. I typically go at least 6,000 to 7,000 on synthetic but the motorcycle doesn't get nearly as many miles so will change it once a year.
 

sq225917

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It depends on several things.

A new car used infrequently still has a cleaner engine interior and sump that an older one. So even sat around doing nothing your oil will last longer than in an older car.

Oil breaks down with heat, age and contaminants. If I was driving a porsche I'd be changing every 5k, but I drive a 15 year old ford focus that doesn't care about oil as long as it has some. It's more tractor than sports car.

If I drove a high power, high revving turbo car or mulitpoint injection engine then I would be more careful. I got over 200k out of my last car so I guess I'm on the right track
 

JustJones

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I have a 2009 Honda Accord and I've only had it changed when the oil change light comes on. I didn't change it for 2 years during the pandemic. I've also got a 2020 Subaru Outback which I have never changed the oil since the light has never come on it only has 5500 miles on it.
 

Chrise36

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Full synthetic should be good for 2 years. Engine wear will be different according to oil quality.
 

Doodski

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I have a 2009 Honda Accord and I've only had it changed when the oil change light comes on. I didn't change it for 2 years during the pandemic. I've also got a 2020 Subaru Outback which I have never changed the oil since the light has never come on it only has 5500 miles on it.
Ouch! My 2nd wife's Honda Civic VX never saw oil changes. She asked me one day to look at her car because a red light was coming on in the middle of corners. So... Of course the oil was a liter below the lowest level on the dipstick. It smelled like it had burned it had aged so badly. The mechanic advised, "No long distance trips, stay in the city and no performance driving." All due to the lack of oil. She killed a car engine. :D Too bad it was a great commuter car and was fun to drive.
 

ta240

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Depending on how short the short trips are; I've heard that too many short drives can lead to moisture in the oil if it doesn't get hot enough to cook off condensation.

You could send a sample of the year old oil off for analysis.

I'm still big on keeping up oil changes but there are so many expensive sensors and fancy electronics on modern cars that I can't imagine engine wear being what eventually puts a car out of commission (unless it is really abused). It isn't like the old days where it was either an expensive engine or transmission repair that would most likely cause people to scrap a car.
 

Spkrdctr

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Regular oil changes at 5000 will keep your vehicle in great shape. In some cars you can go longer, but why? Your vehicle likes fairly clean oil. Waiting until it is a black goo is not wise. YouTube has thousands of videos on engines that did not get their oil changed every 5000 and as they age it just gets really bad. The factory oil sensors allow you to go too long between oil changes. The easiest way to know for sure is to have an oil analysis done at 5000 and then 7000 miles and see if the 7000 is still good to go. More than 7000 no freaking way. I have been around engines my whole life and most people do not change their oil often enough. The black goo that comes out is the Grim Reaper for engines, especially those with oil pressure VVT systems. Those absolutely must have regular oil changes. Think Toyota ect.
The single worst engine that must have 3000 mile oil changes is the Dodge/Chrysler 5.7 Hemi and the 392 Hemi. They need clean oil or you lose the lifters which is a common problem with those engines. The inspections show that most of those lifter issues had not had clean oil changes done regularly and the owners ran them with dirty oil and the lifters go out. A word to the wise.
 

Bugal1998

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I have an ICE car which is driven about 2000 miles per year. Use is split between short and long trips in a warm climate. It came with synthetic blend oil but now runs full synthetic. Everything I could find says never go more than a year between oil changes without regard to mileage. However, I have been unable to find any objective data showing how much slipperiness the oil loses simply due to the passage of time. Is such objective information available or is the one-year interval something left over from the days before synthetic oil, a manufacturer's CYA or an old wives' tale?

I used to frequent the oil and lubrication forums, which sent me down the path of oil analysis.

I once went 45,000 miles on an oil change (filter changes every 10k with top-off oil as needed) based on oil analysis. I got rid of the car at 230k miles and it still ran fine. That was back in the late 90's.

With manufacturer endorsed extended drain intervals I now just follow the manufacturer recommendations. I drive so little these days that means annual oil changes... But I suspect oil analysis would suggest even the annual change is unnecessary.
 

Timcognito

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I look at the color of the oil (name brand synthetic) if it stays clear and amber no reason to change. On my little Tacoma with the 4 cylinder, I haul all kinds of stuff in it, including long trips to my son in Portland OR from SFBA, I only do one oil change a year. The oil light comes on every 5k and I reset it. The oil is just slightly changing color at 12K miles.
 

Propheticus

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I would just read the manual or look up the maintenance interval advised by the manufacturer. It varies a lot between different brands, engines, model years.
E.g. for my Ford Fiesta 3cylinder 1liter from 2019 the interval is 2 years or 30k km (18.5k miles)... That's a good deal more than the 5k miles some multi liter performance engine might require.
 

LTig

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AFAIK many of the modern compact VW models have a 2 year oil change interval if you drive not too much.
 

Blumlein 88

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With synthetic you used to be told every 2 years. One thing has changed which shortens mileage and to some extent time between intervals. That is the use of variable valve timing on engines. Such systems are overly sensitive to oil degradation, cleanliness and viscosity change. And on many cars fixing those issues can be very expensive.

If you drive it on at least one 20 mile trip every 3 months, I'd feel good about going 2 years between changes. Otherwise one year. A 20 mile trip is enough to drive out any moisture and gasoline accumulated in the oil from sitting and short trips. You could get an oil analysis at 1 year and 2 years the 1st time to confirm everything is good. If it is then just go with 2 year intervals thereafter.
 

Timcognito

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If you drive it on at least one 20 mile trip every 3 months,
That may good for the oil itself but not oil seals, AC, transmission, tires etc if the car is sitting in one place. 20 mile round trip every two weeks is much better and that maybe the biggest maintenance issue for the OP not his oil stability.
 

A Surfer

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Ouch! My 2nd wife's Honda Civic VX never saw oil changes. She asked me one day to look at her car because a red light was coming on in the middle of corners. So... Of course the oil was a liter below the lowest level on the dipstick. It smelled like it had burned it had aged so badly. The mechanic advised, "No long distance trips, stay in the city and no performance driving." All due to the lack of oil. She killed a car engine. :D Too bad it was a great commuter car and was fun to drive.
What a shame. I hesitate to generalize here, but the only woman that I have ever known to even remotely care about her vehicle was my mother. I know that is a gross generalization, but seriously, it isn't just with vehicles, the "general" trend I have noticed is for women to really care less about mechanical, or electronic stuff. It seems they just expect to buy, it bang it around and it should look after itself with no user intervention involved. I freely admit that my sample size for these observations is not massive, but it is greater than one!
 

Blumlein 88

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That may good for the oil itself but not oil seals, AC, transmission, tires etc if the car is sitting in one place. 20 mile round trip every two weeks is much better and that maybe the biggest maintenance issue for the OP not his oil stability.
Well op said short and long trips, so I assumed it isn't sitting 3 months at a time.
 
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