i know this topic has been beat to death on this and various other sites. I have to say I have never used anything aside from alcohol and paper towel to clean engine wheels and track. Also over time the cups do build up dirt. It is the turnouts that cause the problems. Here is where you say no problems with powered frogs! If I can keep track real clean it runs quite nicely. Do you find using paint thinner works longer between cleanings for any other reason?
I used alcohol for the first couple years of the layouts life... The mineral spirits have done much, much better. And I don't go nuts trying to wipe all the mineral spirits off the track/rail. Some have said alcohol leaves a film, other's have said it's because rubbing alcohol does contain water also... Whatever, I just know in my experience the mineral spirits have done a better job. Test. It's not like a container of mineral spirits is going to set you back much.
3/4 of my turnouts have unpowered frogs, and if a loco stalls, 7 times out of 10 I find that it's a loco problem (many times with the axle cups, sometimes with the brass wiper strip). Maybe another 2 times out 10, the turnout points are dirty.
Yeah, the unpowered frogs are problematic, but it comes down to the locomotive in most instances IMO... Especially if you're running loco's where each wheel is or should be providing pickup. If/when one truck hits that unpowered frog, the other should be doing its job, and if it's not– then we've got an issue with the loco.