doc-rice said:
Do any of you go the extra mile and clean under the car?
mikebai1990 said:
Yes, I believe many people on the forum do thorough cleanings of their undercarriage..
Yeah, that'd be me

I do the undercarriages pretty much *every* time I wash, even keep a pair of floorjacks and a set of jackstands in the wash bay just for that purpose. It's sorta surprising how dirty the undercarriages get; I never fail to get plenty of dirt off, even when they still looked clean.
What I use depends on the vehicle. Drivers/beaters get an APC, garage queens get a sorta-strong shampoo mix. Both are sprayed on from spray bottles, allowed to dwell, agitated with brushes, and then rinsed off.
Some vehicles get the undercarriages waxed/sealed/dressed, some don't.
In the winter I first rinse things off with the undercar wand from American Waterbroom, with hot water it does a good job of getting a lot of the salt off quickly. Not enough by itself though, I still need to get under there and really clean things off.
When I get a new used vehicle, I do the inital cleaning with solvents, degreasers, and the steamer. After that it's just maintenance and I don't have to redo things in a big way for quite a while.