New Insight On Oil Change Intervals

[zippinbye]

I have always been a sceptic that engine oil must be changed based on an in-service interval, independent of miles or hours, especially in a dry climate like the Desert Southwest. Having grown up in British Columbia and Washington, I "get" the concern of moisture infiltration into the crankcase, be it from condensation while sitting or extracted from intake air during operation. But here in Vegas I have never found moisture in any piece of machinery from tractors to airplanes to any road vehicle. In light aircraft, one of the preflight activities involves pulling a fuel sample from a low point sump in the system. In the Northwest, an ounce or two of water might be detected and discarded rather frequently, but down here, never a drop. My engine oil analysis shows a similar contrast.

I have extrapolated this anecdotal comparison into my rationale for how I manage oil in my four stroke engines that do not accumulate many hours or miles, especially those running full synthetic, like Mobil 1 or Rotella T6. I've always thought the old-school 3000 mile/six month standard was wasteful, both to an owner's wallet and the environment. The Cummins ISB in my pickup gets changed once a year. Usually that's about 6000 miles. I took it to 10,000 on one occasion. Oil analysis was fantastic, even on the high-mileage change. Doing the same with our ISL in the coach. All our gas cars hit mileage before age running Mobil 1 (now Kirkland Full Synthetic), using 5000 or 6000, depending. Lawn mowers, tractors and other miscellaneous small gas engines get changed when I feel like it. I've never had a failure or wear-out of any internal parts, and some of my equipment is 40 years old.

Anyhow, agree or disagree on how I deal with oil changes, but consider having a look at this YouTube video from Project Farm:

https://www.youtube.com/watch?v=T-yt5a1cWd4

They compare two brands of popular synthetic diesel oil, both in its new state and after an extreme service interval. The "Cliff Notes" are that Rotella T6 is a good oil choice, and time in the crankcase does not really matter. If you have not followed the Project Farm Youtube channel, it's worth a look. They do equipment comparisons that surpass anything I've ever seen Consumer Reports do. They dive deep and use a number of sophisticated and inventive analysis tools. Videos I have been impressed by include their rankings of the best chainsaws, both gas and cordless electric, jumpstart packs and rating small gas generators, hydraulic wood splitters and a run-off between a Honda 6 h.p. one cylinder engine and a cheap Chinese copy and a similar engine from Harbor Freight (Predator) - the latter two at 25% the cost of the genuine article (Honda is great, but the others are decent and by far the best value).

After getting this bit of justification, I have no immediate plans to change the T6 in the ISL. Probably will after a big road trip this spring. It currently has 12 months and 2000 miles in-service. Since getting the coach, we have only done a series of short trips, between 90 and 150 miles away from home. Blame COVID for most of that limited distance. Even then, I doubt we will ever log the miles necessitating a change in less than a year.

[Iceclimber]

I am getting ready to change my Cat C-7 at about 5k miles which may seem soon to some. Roughly $90 for 22 quarts Rotella T-4 and $15 for the filter so cheap insurance from my perspective. I have never bothered with testing, I know many folks swear by it.

[Rob_M]

Originally Posted by zippinbye

I have always been a sceptic that engine oil must be changed based on an in-service interval, independent of miles or hours, especially in a dry climate like the Desert Southwest. Having grown up in British Columbia and Washington, I "get" the concern of moisture infiltration into the crankcase, be it from condensation while sitting or extracted from intake air during operation. But here in Vegas I have never found moisture in any piece of machinery from tractors to airplanes to any road vehicle. In light aircraft, one of the preflight activities involves pulling a fuel sample from a low point sump in the system. In the Northwest, an ounce or two of water might be detected and discarded rather frequently, but down here, never a drop. My engine oil analysis shows a similar contrast.

I have extrapolated this anecdotal comparison into my rationale for how I manage oil in my four stroke engines that do not accumulate many hours or miles, especially those running full synthetic, like Mobil 1 or Rotella T6. I've always thought the old-school 3000 mile/six month standard was wasteful, both to an owner's wallet and the environment. The Cummins ISB in my pickup gets changed once a year. Usually that's about 6000 miles. I took it to 10,000 on one occasion. Oil analysis was fantastic, even on the high-mileage change. Doing the same with our ISL in the coach. All our gas cars hit mileage before age running Mobil 1 (now Kirkland Full Synthetic), using 5000 or 6000, depending. Lawn mowers, tractors and other miscellaneous small gas engines get changed when I feel like it. I've never had a failure or wear-out of any internal parts, and some of my equipment is 40 years old.

Anyhow, agree or disagree on how I deal with oil changes, but consider having a look at this YouTube video from Project Farm:

They compare two brands of popular synthetic diesel oil, both in its new state and after an extreme service interval. The "Cliff Notes" are that Rotella T6 is a good oil choice, and time in the crankcase does not really matter. If you have not followed the Project Farm Youtube channel, it's worth a look. They do equipment comparisons that surpass anything I've ever seen Consumer Reports do. They dive deep and use a number of sophisticated and inventive analysis tools. Videos I have been impressed by include their rankings of the best chainsaws, both gas and cordless electric, jumpstart packs and rating small gas generators, hydraulic wood splitters and a run-off between a Honda 6 h.p. one cylinder engine and a cheap Chinese copy and a similar engine from Harbor Freight (Predator) - the latter two at 25% the cost of the genuine article (Honda is great, but the others are decent and by far the best value).

After getting this bit of justification, I have no immediate plans to change the T6 in the ISL. Probably will after a big road trip this spring. It currently has 12 months and 2000 miles in-service. Since getting the coach, we have only done a series of short trips, between 90 and 150 miles away from home. Blame COVID for most of that limited distance. Even then, I doubt we will ever log the miles necessitating a change in less than a year.

If oil analysis says you’re doing the right thing, in my mind that’s all that matters. If there was anything in the oil that would harm your engine the analysis would pick that up. In fact I’m waiting for SOS results from CAT right now as I pushed my oil change this time to 8,000 miles. Target was 7500 miles but life got in the way. I’ve never paid any attention to time, or time of year, only mileage. Previously I was changing at 5,000 - 5,500. Using CAT 15W40 DEO in my 2002 8.3 Cummins with 58k miles.

If one chooses not to use oil testing to verify and possibly extend oil change intervals then 5,000 miles or once a year is a very safe way to go.

[Crasher]

I changed the oil in our Bus (8.9 liter Cummins) once a year which was 10,000 miles. The service tech told me that with the type of service the engine had in the MH, I could run it for 15,000 miles between intervals or once a year. It is an absolute waste to change a diesel engine with a 28-30 quart crankcase capacity at 5-8000 miles. I change my 5.3 liter chevy with a six qt capacity when it tells me to which is usually 7500 miles. At 85,000 miles it still does not use any oil between changes. I suspect that 90% of all owners throw away perfectly good oil long before it's needed by changing too soon. I know you will say oil is cheap and you sleep better after the change, but it's still wasteful of a natural resource.

Edit: Many years ago, I read of a guy ran a Chevy Malibu for 18,000 miles on the same oil. It was an experiment to determine how long oil could do it's job. He took an analysis every 3,000 mile. At the 18,000 mile mark it started to show a break down of the oils lubricity. And that was with a 5 quart capacity. The modern day oils are even better than 30-40 years ago.

[NevadaNick]

Manual with our ISL said 20k mi, i change my Cummins pickup at work every 15k

[DRM901]

I TEST the antifreeze & oil annually in our 2014 Tiffin Allegro Bus. So far, after 2 years and 10,000 miles both come back great & good respectively. The generator I'm testing every 2 years.

https://jglubricantservices.com/

Just changing it doesn't tell you if there are issues starting to arise. I prefer to know.

[F4Gary]

I don't have any diesels, so I change my oil every 5000miles or 1 year.
I also don't use diesel oil in my gas engines. Synthetic oil is cheap at Walmart.

[jharrell]

Cummins on 2021+ ISB's like mine now recommend up to 30,000 miles or 18 months with 10w-30.



I will probably still do it every 12 months and will never hit the mileage limit in that time. Still trying to figure out which oil for my first change, probably Mobile Delvac Extreme since its not too expensive and has a lot of ZDDP, might even do 15w-40 as thats still approved for warmer weather (no hydraulic lifters on the MH version of the engine).

[FLRosebud]

Back in the mid 1990's I was part of the predictive maintenance program at the Kennedy Space Center. We could perform all of the oil testing (ferrographic analysis) and we did a study on Mobil 1 synthetic oil and mileage. For gas engines, we found we could go over 15,000 miles before the viscosity was compromised. I've done that on all of my cars/SUV's since then and have had no issues. I would change the filter every 7,500 miles (living in FL we did get silicone particles in the oil).

However, the Mobil 1 engineer told us don't even bother with Diesel engines, because the sulfur by-product as a result of diesel combustion would break down the viscosity very quickly. We found that at around 3,000 miles we would start seeing this. Now, keep in mind this was on engines that had 5 or 6 quarts of oil. We did not do any testing on the large engine diesel fleet at that time. I would assume that if a DP has 15-20 quarts 6,000-10,000 miles would be reasonable before viscosity breakdown. That is just an assumption, so I think it's important to test the oil before you do any oil change. Like someone else said, I, too, questioned the 3 months/3,000 mile change interval for gas engines. Our testing showed I had a good reason to question. I am surprised so many still use that for their oil changes. Old habits are hard to break, even if the manufacturer recommends longer change frequency.

Al

[theoldwizard]

Modern synthetic and semi-synthetic oils are amazing ! The biggest problem is water/moisture in the oil from multiple heat/cool cycles caused by short trips.

Using a synthetic oil under non-severe conditions, I would have no problems going 10K+ ! Check the level often.

[Ray,IN]

Originally Posted by Crasher

I changed the oil in our Bus (8.9 liter Cummins) once a year which was 10,000 miles. The service tech told me that with the type of service the engine had in the MH, I could run it for 15,000 miles between intervals or once a year. It is an absolute waste to change a diesel engine with a 28-30 quart crankcase capacity at 5-8000 miles. I change my 5.3 liter chevy with a six qt capacity when it tells me to which is usually 7500 miles. At 85,000 miles it still does not use any oil between changes. I suspect that 90% of all owners throw away perfectly good oil long before it's needed by changing too soon. I know you will say oil is cheap and you sleep better after the change, but it's still wasteful of a natural resource.

Edit: Many years ago, I read of a guy ran a Chevy Malibu for 18,000 miles on the same oil. It was an experiment to determine how long oil could do it's job. He took an analysis every 3,000 mile. At the 18,000 mile mark it started to show a break down of the oils lubricity. And that was with a 5 quart capacity. The modern day oils are even better than 30-40 years ago.

Cummins published oil change interval for the ISL is 20,000 miles or annually. https://liferebooted.net/2018-phaeto...aintenance.pdf

[1972VWbus]

I've done several oil analysis tests on mine over the last 9 years and none have ever reported any water accumulation (Seattle area). RV is in storage from ~ Oct thru April/May.

I changed the oil that is in it now back in 07/14/2022 with 479 miles on it currently. I plan on running it until it gets close to 7500 miles then do another test. It has Mobil 1 Extended Perf. 10w-30.

[Winemaker2]

I wonder why the magic " or once / year" clause that is so common?
What is everyone's rationale why they follow that mfg guideline when they are comfortable violating a mileage guideline?

I've done oil analysis at 12 mos with relatively low miles / hours and the results always came back to continue running and retest @ XYZ miles / hours.

The usual argument I hear is " it's acidic and you don't want it sitting in engine in storage". IMO that's completely untrue as the analysis reports how acidic/basic and the remaining TBN # that is there to neutralize the acid. I'm assuming it's a carry over (myth) from hi sulpher fuels that produced more acid / faster... but even then the TBN was a measured # and part of the decision when to change vs continue to run.
I'm trying to understand (not argue) if there is something magic (and not measured) that happens as modern oils age?
I'm just now reading that some eng mfgrs (Cummins) have extended the timing to 18 mos and have to believe that is still conservative or they wouldn't have extended it.

[thegats1]

I recently used a lab (JG Lubricants) to test my coolant. The results were out of spec on hardness (Severe by their standard). Anyway, working through this now. As for the oil, I just changed it the other day, but I am considering what many others are doing and have it tested once per year by the same lab to see where I stand. However, I know zero about the filters. If owners extend the life of the oil, is the filter good to continue using? I'm not sure what the filter media is and whether it will begin to break down.