WD40 isn't water based, it is a Water Displacer, many use it during the parkerizing process, sprayed on the steel part after it is pulled from the acid solution and rinsed, the WD40 raises any water to the surface and whatever petroleum distillate in it prevents the steel from rusting.
I served two tours of duty in the Berlin Brigade (Feb 89-Dec 90; Oct 92-June 94), aside from being tough and nit-picky, we had parade season every year. We would have the Allied Forces Day Parade on 17 June downtown from the Brandenburg Gate then Westward, then 4th of July Parade on the huge asphalt drill field next to our barracks in Lichterfelde, names Platz des 4. Juli 4th of July Place (or square). So for the whole month proceeding the parades we'd be practicing at Company level, then battalion, then full dress rehersal as Brigade level (entire Allied Forces for the 17 June parade).
Dress was Class A Greens, Infantry Blue Ascot, PASGT Helmet with brand new woodland camo cover, M16A2 Rifle with fixed M9 Bayonet, spit-shined Jumpboots. There would be a few examples of each vehicle type driven in the parades, from slant back HMMWVs, M113A2 (and M125A2 81mm mortar tracks and M106 4.2in mortar tracks), M1 Tanks, 5ton wreckers, M88 Tank Recovery Vehicle, and the Allied equivilents. So the chosen vehicles wound up getting sent to the 3 shop for a fresh paint job in the NATO 3 color camo, and the vehicle crews would go beyond the fresh paint for the dog and pony shows.
I've seen everything from using black boot polish on the HMMWV tires and the track rubber roadwheels, WD40 on the paint, even baby oil or Future Floor Wax used on the paint and vinyl rag tops. Everything was polished up, shiny, not flat green factory finish. WD40 being a petroleum distillate probably wasn't very good for the PVC coated nylon used to make the rag tops then and now.
Future liquid floor wax would dry, change colors, crack then flake off. Baby oil (mineral oil plus additives) would become dull after a few days but just took a shammy-like rag wiping on a fresh coat to bring it back. It also helped water to bead off not leave spots but it didn't damage the PVC-coated nylon rag tops.