Maintaining Cummins ONAN generator

[Bill]

I have a 9500 watt generator, we use it exclusively for power backup in our home. Only run it on LP gas. It has 21 hours of runtime on it, works great and starts right up. We lost power for 11 hours yesterday afternoon to 3 am- it was great to have.

The Cummins service manual says to change oil at 25 hours, then at every 50 hours or 6 months if not used.

I checked the oil level and it was perfect, and looks new.

- Does it really need 25/50 hour oil changes if the oil looks new? Change oil every six months if not used?

- Conventional or synthetic oil?

- Reuse crush washer or track one down new ones at the local NAPA?

The cost and time are not the issue- I’m just curious if it really needs oil changed that frequently.

[SaltwaterSlick]

Bill, you should do the minimum requirements to make sure you maintain your warranty period. Once that is past, based on my experience with small engines, and specifically Onan generators, be your own judge... Many years ago, I ran an experiment on engine oils in one of my company vehicles. I sold research and testing pressure equipment and systems to virtually all the major oil companies and I had one in particular that I was very close with in the Houston area. I ran their branded oil in my company vehicle and removed it every 3,000 miles and had them test its lubricity qualities. The oil maintained over 85% of it's lubricity qualities beyond 18,000 miles. The most important thing to maintain good oil quality is a quality filter. The quality of motor oils has improved vastly since that time (mid-'90's).
Regarding synthetic or not, I'd go by the manufacturer's recommendations there. The thing that is important there is the soft parts in the engine such as gaskets, o-rings and other seals. The materials of soft seals/gaskets can react to different types of oils. That's what those numbers and letter classifications are on the oil bottle in the SAE rating logo. If the manufacturer indicates that either is acceptable, just pick one that is easy and cheapest for you and go with it. But it is not good to mix them. The oils can and often do react badly with each other.
Generally, synthetic oils will maintain their lubrication qualities longer than conventional oils.

[Bill]

Thanks for information. I looked at the ONAN service manual again for the synthetic oil weight, and noticed in 1 section it says 25/50 hours and then in the table to check every 100 hours. You can’t check oil every 100 hours if you change it every 50, can you?

I’ll change it with 5-20 synthetic and probably change at 50 hours.

With your background and oil, let me ask you another question. 40 years ago when I was in college, I remember reading a little blurb and a technical journal about an engineer at NAStA Lewis in Cleveland. He said he experimented with tricresyell phosphate, as an oil additive in the research centers large generators.

They would pull oil samples and analyze for trace metals to for preventative, maintenance, particularly with bearing wear. He wrote that he found 90+ percent reduction in engine wear using that additive at 5%. He also recommended it be used in all US government vehicles, to make the engines run for almost ever.

I remember tracking him down on the telephone, and he said it was such a radical idea, and how many less cars would get sold to the government. He was told to **** up and transferred to NASA in Huntsville, Alabama as punishment. He explain, whenever pieces of hot metal did not have a thin film of oil, the temperature at that little spot would get so hot that the engine would be phosphated as the TCP vaporized. The same as Parkerizing a rifle barrel.

Have you ever heard of Tri Cresswell phosphate as an engineer oil additive?

[Greenheadless]

Checkout ‘The Motor Oil Geek’ on Youtube

[tps7742]

Bill, you should do the minimum requirements to make sure you maintain your warranty period. Once that is past, based on my experience with small engines, and specifically Onan generators, be your own judge... Many years ago, I ran an experiment on engine oils in one of my company vehicles. I sold research and testing pressure equipment and systems to virtually all the major oil companies and I had one in particular that I was very close with in the Houston area. I ran their branded oil in my company vehicle and removed it every 3,000 miles and had them test its lubricity qualities. The oil maintained over 85% of it's lubricity qualities beyond 18,000 miles. The most important thing to maintain good oil quality is a quality filter. The quality of motor oils has improved vastly since that time (mid-'90's).
Regarding synthetic or not, I'd go by the manufacturer's recommendations there. The thing that is important there is the soft parts in the engine such as gaskets, o-rings and other seals. The materials of soft seals/gaskets can react to different types of oils. That's what those numbers and letter classifications are on the oil bottle in the SAE rating logo. If the manufacturer indicates that either is acceptable, just pick one that is easy and cheapest for you and go with it. But it is not good to mix them. The oils can and often do react badly with each other.
Generally, synthetic oils will maintain their lubrication qualities longer than conventional oils.

interesting information on your oil lubricant test results. Thanks for sharing this information and very interesting results.

[jmoore2006]

If it is an air cooled unit I highly recommend 25 hour continuous use oil changes. Living on the Gulf I can't tell you how many people I've seen through the years just run them until failure. The oil temp on the air cooled units work against the oil holding up for longer service intervals. As far as intermittent small use i think every 6 months will be fine. And pushing the 25 hour service to 50 truly would depend on the load you are putting on it and how long it is running loaded. If you are only using some fans and keeping the fridges cool i wouldn't worry about a 50 hour service interval. But as the load increases your oil service life will decrease.

[Bill]

Thanks for comments!

[Johnny Dangerr]

Changing the oil in our Kohler this week. It has been 2 years almost to the day. I check the oil regularly and it looks like it did when I poured it in.
Three years ago it ran 9 days straight during the big freeze. Around 200 hours I guess...

[SaltwaterSlick]

Thanks for information. I looked at the ONAN service manual again for the synthetic oil weight, and noticed in 1 section it says 25/50 hours and then in the table to check every 100 hours. You can’t check oil every 100 hours if you change it every 50, can you?

I’ll change it with 5-20 synthetic and probably change at 50 hours.

With your background and oil, let me ask you another question. 40 years ago when I was in college, I remember reading a little blurb and a technical journal about an engineer at NAStA Lewis in Cleveland. He said he experimented with tricresyell phosphate, as an oil additive in the research centers large generators.

They would pull oil samples and analyze for trace metals to for preventative, maintenance, particularly with bearing wear. He wrote that he found 90+ percent reduction in engine wear using that additive at 5%. He also recommended it be used in all US government vehicles, to make the engines run for almost ever.

I remember tracking him down on the telephone, and he said it was such a radical idea, and how many less cars would get sold to the government. He was told to **** up and transferred to NASA in Huntsville, Alabama as punishment. He explain, whenever pieces of hot metal did not have a thin film of oil, the temperature at that little spot would get so hot that the engine would be phosphated as the TCP vaporized. The same as Parkerizing a rifle barrel.

Have you ever heard of Tri Cresswell phosphate as an engineer oil additive?

Bill, I've seen a few different additives used over the years, but I do not have detailed knowledge/experience in that area. The one thing I did get somewhat involved with was in coatings research with one of my customers in the Houston area. Guy's name was Sam Butler. He was quite well known for his development research in oilfield equipment bearings and seals. He also worked with AJ Foyt on bearings in his "Fox" engines. He came up with this stuff he trademark named "Impreglon". It was widely used in oilfield rotating equipment as well as in Foyt's racing engines. That however was a coating for bearing surfaces and not an additive.

As jmoore2006 posted above, air cooled engines under heavy load run hotter than normal, and in a generator application, the load indeed would make a big difference in oil life and bearing wear. My biger Honda generator (EU6500i) recommended the first oil change at 25 hours and then every 100 hours or annually. That thing has a LOT of hours on it now, and still it's never checked low on oil, nor has the oil ever looked "used"... The oil I drain out of it looks pretty much like the new oil I'm putting back in it!

The guys I used to work with as a customer in the oil lubricant business were doing development work on the Rotella line of oils. That ought to give you an idea of how long ago that was.

[Bill]

I googled tricresyl phosphate and NASA and there were multiple tech papers written in the late 80s about it’s anti wear properties in oil. I read the article while in college before 1980. It’s used in some aircraft engine oils. I guess it wasn’t a secret locked away by the government at the urging of the auto manufacturers.

[SaltwaterSlick]

You mean like the engine that runs on water was?!

[Bill]

You mean like the engine that runs on water was?!

Funny. I remember working as a chemist and calling the fellow after tracking him down. In 1980, he told me that after writing a report and a memo to his management, they proposed it for all government vehicles to make them last 'forever', he was transferred from NASA Lewis (where the papers I found on the Google search) were authored to NASA in Huntsville.

[SaltwaterSlick]

Funny. I remember working as a chemist and calling the fellow after tracking him down. In 1980, he told me that after writing a report and a memo to his management, they proposed it for all government vehicles to make them last 'forever', he was transferred from NASA Lewis (where the papers I found on the Google search) were authored to NASA in Huntsville.

DuPont used to be one of my biggest customers here on the Gulf Coast. They had 3 different chemical/petro-chemical R&D facilities here that I called on. The running joke (that was really not a joke) was after DuPont bought Connoco Oil, if you screwed up but not bad enough to get the axe, you'd be "promoted" to Ponca City! One of my favorite lab Techs that I worked with indeed messed up and got the "promotion"...