I bought a new toy hauler last year and had a new Onan generator added to the purchase. I think it is a 2016 model generator. I looked up Onan on line and there was absolutely no one who could give me any information on maintenance of this generator. I've looked elsewhere on line and everyone says that it does not have an oil filter. Not too familiar with these generators but I do know that in a normal motor, the oil filter is usually the most important part of keeping the oil clean. I just can't imagine this not having a filter to change out. The dealer where I purchased the generator didn't leave an owners manual and the Onan manufacturer said that they didn't have one and couldn't tell me where to get one other than the dealer. I've heard a lot of good things about these generators and mine has performed thus far without fail. However, I'm not too sure I care for the company's help and customer service. Can anyone help here?

Googled your part # and came up with this:https://www.norwall.com/products/Cummins-Onan-QG-4-0-Gasoline-RV-Generator-4.0KYFA-26100

If it were me...I'm not sure if this is Cummins/Onan dealers nationwide of just my dealer, but take model number and serial number to a dealer of your choice and do two things. 1. Have them enter your data into there data base so they can contact you if any recall notices and also when getting any parts all they have to do is look your info up. And when there ask to buy an oil filter, which will solve your problem.2. My 4ky same size but older does not have any filter. And I asked the same question first time I changed my oil also.

This link shows a fuel filter but no oil filter.

Moved to Tech Issues forum from DIY.

It's good to always post the Model Number and Spec Code for an ONAN Generator. And you did, and KY Series has NO Oil Filter. We have a much older 4KY and I wondered the same thing. Turns out 4KY has a Splash Lubricated Engine. Like many mower engines. It's also a high-rpm engine, and it's air cooled. It has to have breathing room in its installation, BUT it MUST have its Access Panel in place! Leaving that Panel off breaks the cooling air flow pattern.Bigger ONAN's, and older small ones in the 4KW range, have twin-cylinder, low RPM, pressure lubed engines and those have oil filters. Not 4KY. May sound cheesy, but they'll still run a long time. Just use good oil, keep it full, change it often, and let it get air.OH! Exercise it as prescribed in the manual. And, use stabilizer like Startron or Stabil, in all your gas.EDIT: The post above included a link about 4KY, and within that link was another link, to the ONAN 4KY Operator Manual. I looked and it's pretty detailed.Earlier versions of 4KY had a "Low Oil" cutoff switch. If it thought your oil was low, it'd stop the generator. Apparently it kept more engines With Oil From Running than it saved engines with Low Oil, and it's been removed from the 4KY series for years. Ours is Spec "K" and it was gone before then, and you're up to Spec "P!" So if yours doesn't run one day, somebody'll say "Low Oil" or "Bad Oil Switch" and it won't apply to you. I say that thinking (but not verifying!) that ONAN hasn't found a way to add a switch back in there again... It DOES mean all of us with 4KY's need to pay attention to the Oil Level, and that Manual says how to check it.

Does an Onan 4000, Model # 4KYFA-6747P have an oil filter?

11 Replies

cgmartine
Explorer
Aug 13, 2017
Might I be rude and jump in here and ask a question? I would like to change the fuel filter in my K series 4000 Onan. I understand it is attached to the fuel pump. I also understand you have to remove all the electronics from the front in order to get to the fuel pump. Has anyone done this? This sounds like a major job.
Chum_lee
Explorer
Jul 08, 2017
bounder39zman wrote:
Previous posts have good advice, and correctly stating NO oil filter.
This is a splash lubed, 3600 rpm engine so keeping oil clean, full on dipstick is critical. I recommend 15W-40 such as Shell Rotella or Mobil Delvac (or any good brand) as preferred lube. This is what ONAN puts in at factory. Synthetic certainly wont hurt, but wait until engine is "broken in" before using synthetic oil. Oil is cheap compared to a replacement engine, so change it often. Recommend annually, or 100hrs max.

Chevron Delo 400 15W-40 also matches the same specs. I generally use any one of those 3 in my Onan 4KW gas genny. Yes, which ever one is on sale in the 4 qt jug is usually the best deal. They all meet Onans specs. They are "technically" synthetic oils without the synthetic oil price.

Chum lee
bounder39zman
Explorer II
Jul 07, 2017
Previous posts have good advice, and correctly stating NO oil filter.
This is a splash lubed, 3600 rpm engine so keeping oil clean, full on dipstick is critical. I recommend 15W-40 such as Shell Rotella or Mobil Delvac (or any good brand) as preferred lube. This is what ONAN puts in at factory. Synthetic certainly wont hurt, but wait until engine is "broken in" before using synthetic oil. Oil is cheap compared to a replacement engine, so change it often. Recommend annually, or 100hrs max.
Chum_lee
Explorer
Jul 07, 2017
mobeewan wrote:
This link shows a fuel filter but no oil filter.

This has been my experience also. Air and fuel filters only on the Onan 4000.

Chum lee
j-d
Explorer II
Jul 07, 2017
You're Welcome and Welcome Aboard!

Hang out with us, don't just come by when you have an "issue." You'll be answering questions before long.
catfishrebel
Explorer
Jul 07, 2017
Thanks so much to everyone here that replied. You guys are super and I think this info was the answer to all of the questions I had. If any of you are ever on the East side of Dallas and need any assistance, please free to look me up.
j-d
Explorer II
Jul 06, 2017
It's good to always post the Model Number and Spec Code for an ONAN Generator. And you did, and KY Series has NO Oil Filter. We have a much older 4KY and I wondered the same thing. Turns out 4KY has a Splash Lubricated Engine. Like many mower engines. It's also a high-rpm engine, and it's air cooled. It has to have breathing room in its installation, BUT it MUST have its Access Panel in place! Leaving that Panel off breaks the cooling air flow pattern.

Bigger ONAN's, and older small ones in the 4KW range, have twin-cylinder, low RPM, pressure lubed engines and those have oil filters. Not 4KY. May sound cheesy, but they'll still run a long time. Just use good oil, keep it full, change it often, and let it get air.

OH! Exercise it as prescribed in the manual. And, use stabilizer like Startron or Stabil, in all your gas.

EDIT: The post above included a link about 4KY, and within that link was another link, to the ONAN 4KY Operator Manual. I looked and it's pretty detailed.

Earlier versions of 4KY had a "Low Oil" cutoff switch. If it thought your oil was low, it'd stop the generator. Apparently it kept more engines With Oil From Running than it saved engines with Low Oil, and it's been removed from the 4KY series for years. Ours is Spec "K" and it was gone before then, and you're up to Spec "P!" So if yours doesn't run one day, somebody'll say "Low Oil" or "Bad Oil Switch" and it won't apply to you. I say that thinking (but not verifying!) that ONAN hasn't found a way to add a switch back in there again... It DOES mean all of us with 4KY's need to pay attention to the Oil Level, and that Manual says how to check it.
BarneyS
Explorer III
Jul 06, 2017
Moved to Tech Issues forum from DIY.
mobeewan
Explorer
Jul 05, 2017
This link shows a fuel filter but no oil filter.
path1
Explorer
Jul 05, 2017
If it were me...

I'm not sure if this is Cummins/Onan dealers nationwide of just my dealer, but take model number and serial number to a dealer of your choice and do two things.

1. Have them enter your data into there data base so they can contact you if any recall notices and also when getting any parts all they have to do is look your info up. And when there ask to buy an oil filter, which will solve your problem.

2. My 4ky same size but older does not have any filter. And I asked the same question first time I changed my oil also.