Is it me or does the 1990 Onan Generator have two oil fill locations? Appears one located at top center and other is lower front right corner looking at it from the top (inside of coach). It appears this one is located right above filter.

If you don't have a manual, perhaps you can get the PDF here:
http://www.cumminsonanstore.com/

Can't seem to find what model I have to search it. It seems odd that there would be two fill openings but it seems the the tech at Speedco who did the lube and oil changes right when I bought it mentioned that to me (along with a long list of proposed items to repair/check etc)

so can anyone confirm or advise if the 1990 Onan Generator would have two oil fill locations? I am using quite a bit of oil (1/3 to 1/2 qt every 4-6 hours of operation). The unit is not smoking and I do not find any puddles underneath. There is some oil and road grime under, but it is 21 years old.

Although I can't speak to your Onan, many small horizontal-shaft engines have two oil fills. Both my Honda-powered pressure washer and my B&S-powered backup generator have two. This arrangement sounds a bit strange, but it allows flexibility in the design of devices it may power.

The oil consumption is very high. Lack of smoke tends to indicate leakage through the valve guides. Many times they can be knurled and rebored to stop the leakage.

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Originally posted by jer711:
Can't seem to find what model I have to search it.

What is the engine model designation?

I was just looking down at my onan 7.5 and it has two just as you discribe one in the top middle of the valve cover and the second in the front right. They do this for ease of maint. like in our cases we would fill from the valve cover, if this genset were in a side compartment you would use the one on the side. The filters are also located on that side. I have to add what a neat little unit they are, little 3cly. baby genie in my big Baby Baby!

Had to do it

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little 3cly. baby genie

Wharf, is yours a diesel also?

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Originally posted by Patch1st:

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little 3cly. baby genie

Wharf, is yours a diesel also?

Yes it is a diesel, nice looking setup has 2330hrs on the clock and runs good nice and quiet too. (knock on wood)

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Yes it is a diesel

Your unit is VERY similar to mine.... I also have that 3 cyl. Kuboto and an 8.2 DD in a 1985 35' Regency.... I also have in my possesion a few shop manuals for those two engines.... If you need to know any tech data on them just send a PM.....

so where is all my generator oil going? While sitting, there is no evidence of an oil leak (no puddles anywhere). While running, after 4-6 hours, the oil pressure drops significantly and after checking oil, it is way low. But again, looking underneath, no evidence of a leak. Also, no visible signs of burning oil - no smoking, smell of oil etc from the generator exhaust. Tech who fixed the bad wire causing overheat warned me of a leak. If it is leaking while running down the road, I assume it has left almost no visible sign of much oil on bottom of pan or surrounding frame. Gennie has less than 1200 hours and recent oil/filter change, but ran several hours before this past trip and big drop in oil pressure. Thoughts?

A diesel engine will often times show no visual signs using oil as it will treat the oil the same as fuel. Sounds like either a broken oil ring(s) or as Rusty said bad valve guides are letting excess oil into the combustion chamber

can these types of repairs be made without removing the generator?

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Originally posted by jer711:
Tech who fixed the bad wire causing overheat warned me of a leak... Thoughts?

Why did the tech warn you of a leak? He must have seen an external leak... right?

I still don't know what engine model you have.

Oil can seep in and burn from many places without your knowledge. Your best bet would be to pay for a proper diagnosis from someone who works on the diesel Onan Generators.