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Old 02-27-2009, 10:29 AM   #1
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Looking for thoughts on the oil change intervals for large diesel engines. I have a 525 Cummins ISM engine, the manufactures recomendation is 18000 miles or one year. The sump on this engine is just under 50 us quarts. The milege driven is about 8000 miles per year. Any input would be great.


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Old 02-27-2009, 11:55 AM   #2
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Hi Ron,
Welcome to iRV2. For me there is no question about this. Obey the Cummins recommendation. For you it would be once per year. Bad stuff builds up in the oil. The once a year recommendation is to make sure all the contaminates are drained out of the engine instead of continuing to contaminate all the parts. If there is a time of storage or extended non-use, consider changing the oil just before this time.

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Old 02-27-2009, 12:31 PM   #3
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Based on a suggestion from my brother-in-law who was responsible for diesel maintenance in the Navy for 25 years, I have gone the Oil Analyzers, Inc. route where you take a sample of oil at periodic intervals and send it in for lab analysis. The lab report then tells you when the impurities and viscosity of the oil is approaching a threshold where it needs to be changed. According to the bro-in-law, the Navy has been doing it this way for years with a tremendous cost savings.

Depending on your situation, you may be getting rid of perfectly good oil. Beside the economic benefit to you, there is also an environmental benefit of minimizing the use and disposal of lubricating oil.
Tom and Katharine
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Old 02-27-2009, 02:59 PM   #4
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My ISC recommended is 15k or 12 mo. I drive anywhere from 6k-9k per year. I have mine changed annually along with chassis lube, etc.
Paul (KE5LXU) ...was fulltimin', now parttimin'
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Old 02-27-2009, 04:25 PM   #5
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Annually unless I reach the required change due to mileage. I usually do about 7000 per year. Time is equally as important as mileage.
Bob Retired Army Traveling alone now.
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Old 02-27-2009, 09:11 PM   #6
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I have yet to reach the recommended mileage for changes so just change annually.
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Old 02-28-2009, 01:46 AM   #7
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Ron, welcome to iRV2.com. We are glad to have you join us here.
I would recommend you do not exceed the maintenance schedule, especially if your engine is in warranty. And that you keep all records of service; document the date and mileage if you do your own changes. This will come into play of you ever have an issue that has to be warrantied by the manufacturer. Good luck and enjoy the website.
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Old 02-28-2009, 03:58 AM   #8
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Tom...I checked out that website and have a question...so your year old oil report comes back that everything is ok for continued use...it doesn't tell you when to recheck it again at $22.50 a pop, plus the hassle of getting a 3 oz sample...so your oil can be fine....until when??? How often do you retest and worry about it in between tests? And then get the dreaded report that it's been too long
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Old 03-02-2009, 03:53 AM   #9
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When you have 50 quarts of oil to deal with I would consider an alternative such as an oil analysis. One thing I am concerned about is acid build up. This is water combing with the sulfur oxide to form sulfuric acid. I had one oil analysis done for a general check on my 5.9L diesel and found the company, Blackstone, to be most helpful. They answered my question and essentially educated me as to what the analysis meant and what it assured me of. Following the guidance that the analysis labs give may let you extend your interval. After a certain amount of testing and getting repeated results you will find your change interval and after that testing will not need to be done every year. BTW my 16 quarts get changed every year because it is just 16 quarts and because I do it myself. I also get a filter change at the same time.
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Old 03-03-2009, 02:20 AM   #10
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Getting the oil sample is not problem as I have a little hand pump with a long tube that goes right down the dipstick tube.

As with any scientific testing, the results you receive follow a normal progression. You don't get 'good oil' with one test and 'bad oil' with the next. You test every year and when the oil is at a point where it APPROACHES 'bad' (or out of the tolerance interval), you change it.

Why guess at something when you can make an educated decision based on fact?
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Old 03-04-2009, 04:24 AM   #11
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We run over 8,000 mi/year on average. Per C ours is good for 1 year or 12 months. So we change it every year...small price to pay to protect the engine.

In addition, about 1/2 through the year we pull a sample (very eay with the pump and some plastic tubing) for a check. This is not to extend the interval but to see if there is any early indication of something going wrong...coolant, bearing, etc.
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Old 03-04-2009, 01:09 PM   #12
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Just as a point of reference - With fire apparatus we go with a 250 hr interval between changes.
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Old 03-10-2009, 09:53 PM   #13
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We change engine oil every year no matter the mileage although above 8G I'd do another change and have purchased a small air grease gun for chassis lube every 4-6 months due moisture or dirty conditions. I have too much motorcycle discipline to not just do it.
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Old 03-10-2009, 10:19 PM   #14
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Cummins does have an extended change interval procedure for most of their engines. It involves different filters and perhaps other stuff depending on your engine. Cummins further specifically disapproves of oil testing as a means for extended intervals. Cummins also provides different specs for engines that are designed for and in use by commercial/industrial/fire and these uses all have differing interval specs. Search the Cummins site for details.

With the Cummins *facts* out of the way, my *opinion* is that RV usage - because of the typically lower miles - usually has time trumping miles. Change that stuff annually. Don't skimp. The filter too. Why play with the life blood of your $30,000+++ engine?????? Consider it a DIY ~$120 or a http://www.speedcousa.com ~$200 insurance policy. And, as was also mentioned above, get it tested just to see what's going on inside that beast. Might be an early warning for you. http://www.blackstone-labs.com

I do my ISM (10 gals or so) DIY using 3 5 gal pails under the un-jacked rig all sitting in a garage floor drip pan. Pull the plug and slide the pails over as they fill. Seldom even a splash. Then funnel them off into smaller resealable containers to shuttle to the recycle tank at the local auto parts. A very straightforward job. Spin off the filter(s) and replace. Rotella from WalMart and Fleetguard filters from Spartan (cheaper than from Cummins). Of course you can hit a SpeedCo for about $80 more than DIY. That's a pretty good deal too!

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