Originally Posted by RCMoeur

Just plain Oil Eater concentrate, mixed 3:1 or 4:1 with water. I buy it by the gallon and use that 4:1 mix in a spray bottle for most parts & bike cleaning. With all the bikes I work on, I go through about 1 gallon of concentrate per year, although if I didn't do so much bike work it would probably last a lot longer.

The other weapon is the Finish Line Clean Streak spray degreaser. This stuff is much more aggressive, and a lot more expensive. And deceptively good at loosening parts. I say this because several years ago at the nonprofits we'd just spray a balky shifter with Clean Streak and many times it would start working again almost immediately. A miracle product! But then a few weeks or months later we'd deal with a disappointed recipient or customer with a shifter that stopped working again - the Clean Streak loosened it up all right, but only temporarily until it evaporated and the old grease re-solidified. And I hate to think of all the others who didn't bring it back and just gave up on having a working shifter. Combining the short-term power of Clean Streak with the slow-but-sure ultrasonic + citrus cleaner seems to be what works to get it all out.

Are there better options? As I recall, you're not supposed to use anything aromatic or combustible in an ultrasonic cleaner, as to avoid voiding the warranty or experiencing an Earth-Shattering Kaboom. If others out there have a better option for the ultrasonic bath, I'd be open to testing it if the cost is within reason. But note that the final baths are in plain hot water to get rid of the remaining residue.