Gas isn't a good idea... It breaks down the foam in the filter and this makes the oil not adhere as well. Some use kerosene but this is after many cleanings and having the filter covered in oil. If I were you I would go buy a cleaning solvent especially made for foam filters. I use No-toil products and it works great. But you have to buy the cleaner, the oil, and the rim grease all at once. The cleaner only works if you had the no-toil oil and rim grease on. It works well and it's worth the money. It's also biodegradeable, so you can do it in the kitchen sink.