bp-guy Posted October 27, 2008 Share Posted October 27, 2008 I have an ONAN 4000 on my motorhome. It doesn't have an oil filter on it so all I need to do is change the oil. My question is--- Is there a specific oil weight I should be using and does ONAN require a certain brand? I know I could just call a dealer to find out but this might help others on here as well as me so I am asking here. Thanks Quote Link to comment Share on other sites More sharing options...
Richard Cheese Posted October 27, 2008 Share Posted October 27, 2008 http://www.cumminsonan.com/rv/ the pages with the manuals are down, but when they were up, they were asking for the model number Quote Link to comment Share on other sites More sharing options...
KEN Posted October 27, 2008 Share Posted October 27, 2008 I have an ONAN 4000 on my motorhome. It doesn't have an oil filter on it so all I need to do is change the oil. My question is--- Is there a specific oil weight I should be using and does ONAN require a certain brand? I know I could just call a dealer to find out but this might help others on here as well as me so I am asking here. Thanks Call Johnnie Walker RV Center....They can answer all your generator questions. I think they even have a generator service special going on now....877-879-4750 ask for Jeremy he is the best over there. Quote Link to comment Share on other sites More sharing options...
White Rhino Posted October 27, 2008 Share Posted October 27, 2008 Tim I always use Onan, I dont know if its required or not, but better safe than sorry. are you sure there is no filter? Camping world has all that shizzle Quote Link to comment Share on other sites More sharing options...
bp-guy Posted October 27, 2008 Author Share Posted October 27, 2008 Tim I always use Onan, I dont know if its required or not, but better safe than sorry. are you sure there is no filter? Camping world has all that shizzle I am positive there is no filter, I looked everywhere and don't see it. I was told that some generators don't have them. Maybe it's because I have a smaller generator. I will use the Onan oil. It only cost $4 bucks a quart and only needs 1.6 quarts. I don't want to be cheap on $8 bucks for the correct oil. Thanks for the input guys! Quote Link to comment Share on other sites More sharing options...
chris1223 Posted October 27, 2008 Share Posted October 27, 2008 (edited) When I worked at Bell Trans they had about 300 of these on the busses for the air conditioner. They did a test and found that replacing 1/4 of the oil with Marvel Mystery Oil really extended the life of them. Edited October 27, 2008 by chris1223 Quote Link to comment Share on other sites More sharing options...
sandseeker Posted October 27, 2008 Share Posted October 27, 2008 I have the same generator there is no filter I was told by my rv guys to use 30 wt mobil 1 synthetic it works real good in mine Quote Link to comment Share on other sites More sharing options...
Reddog Posted October 28, 2008 Share Posted October 28, 2008 I agree with sandseeker, mobil one for most of my toys. Synthetics are proven to hold up longer. Make sure you thread the drain plug by hand. I learned that one the hard way!! Quote Link to comment Share on other sites More sharing options...
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