I use diluted Simple Green for dusty/dirty feed tires.

As for WD-40...the last of our gallon of Fedron ran out about a year ago and not getting anymore. WD-40 has been a good substitute but just not the same capabilities as fedron. Also, I have not been able to carry it in my tools. I use the small glass Tester paint bottles and it will leak out regardless. I have to keep it upright in my other tools.