I've been using No Toil filter oil on my foam air filter and I like it alot. It's biodegradeable so you can just wash it out in the sink with soap & water. If you're still using some solvent to clean the oil out of your filter you should check it out. They do sell a No Toil cleaner that you can put in your washing machine if you want to remove the oil but soap & water seems to work just as well. My son was using it on his dirt bike and I tried it and it makes cleaning your filter alot easier.

 

Interesting...where do you find the stuff? I never heard of it before.