While some parts are not picky and you can use just about any similar model, parts like filters are specifically designed to do a specific job. That means you need to find the right oil filter or your generator will not have the proper protection. You do need to find the right filter for this generator.
There are different filters for different Onan generators in this series- Onan 5500 Marquis generator uses an Onan 122-0645 filter. Then another Onan 5500 uses a 122-0836 filter which corresponds to a Napa FIL7398. You need to go to an auto parts store to find compatible filters from other companies.
To learn more about this issue, just continue to read our article. It has the information you need to know about so you can find the right one for your Onan 5500 generator. For example, the Fram has an anti-drain valve and a bypass valve just like the Onan. The Fram bypass is set at the top pressure range that the Onan is set for.
There is not just one filter. To find the correct one for your specific 5500 model you should either check your owner’s manual or talk to an Onan dealer to find the correct filter. In this series, there is the BGM, NHM, and the HGJ model series and each one takes a different filter.
If you do not care for the Onan brand of filters, and one reviewer only gave them a C+ grade which is surprising, you can always cross-reference the parts number to find a NAPA, Wix, or even Fram substitute.
Here are the part numbers for 3 Onan generator series:
BGM uses the Onan 122-0645
NHM uses Onan 122-0800
HGJ use Onan 122-0836
The Onan Parts website has 3 pages of oil filters. Fortunately, not all on those pages are for the 5500 series. You can look at those pages but the ads may need to be clicked on to find which generator model they are for.
We checked both Walmart and Amazon to see if one of these kits actually existed or not. These two large marketplaces did not seem to have any listed or in stock. The closest we got was an HGJAB Gas Generators Maintenance kit over at RVupgradestore.com
That kit came with 2 quarts of oil, 2 spark plugs an oil, gas, and an air filter and costs over $100. Walmart called it a tune-up kit but it is missing the two quarts of oil. You only have to pay $88 there.
For the BGM series, the oil filter should be in the middle of the right side, depending on which direction you are facing. This places the filter right under the brand name and model name.
This seems to be the location for the marquis model as well. As for other models, you should check the parts diagram in the owner’s manual to make sure.
This may be more of a chore than you realize. Removing an oil filter on a generator is not the same as removing one on a car. They are easier to reach but you may need differently designed oil filter tools to remove them.
Onan seems to like making the end of the filter flush with the exterior walls of the generator. This means you cannot use a standard oil filter wrench to grab the filter. Some use a filter socket wrench to get the filter out but different generator designs may allow you to use different oil filter wrenches.
Amazon sells one model called the Generator Parts Specialists Onan 122-0836 Oil Filter Wrench but it is currently out of stock at the moment. You should be able to find it at your local parts or big box stores in your neighborhood.
Some people go with the NAPA oil filter wrench or some other brand as those companies make compatible wrenches for this task. Amazon also sells compatible models for under $30 approx.
To find the correct one from another company, use the part number above or the one for your generator and cross-reference it with other brands- WIX 57398 and Baldwin B7238 are just two examples.
Amazon has many varieties, including those included in any tune-up kits. They are listed by the part number so you would need to have that on hand to make sure you are getting the correct one for your model.
They also carry compatible models from other brands including Baldwin and Allmost with the latter fitting the Marquis model in place of the gold fuel filter. However, it is probably better to go to a parts store so you can cross-reference if the Onan option is out of stock.
It seems that Onan learned some lessons from different RV makers. They also played hide and seek. Instead of placing the pump & fuel filter inside the generator, they placed them on the underside of the generator base plate.
Your parts diagram should give you a general idea of where these parts are located. the filter is right next to the pump on the fuel line. Keep in mind that models made in different years and different series may have different locations as well. Designs change.
Normally, changing the fuel and oil filters is a routine task. However, with the placement and design of the filter, this easy task can turn into a few moments of frustration.
It is all up to Onan where those parts go and they prefer not to make things easy for owners. The purpose of the generator will also determine the location of these parts.