Some 40 years ago, when I worked for MOD, I was involved in a field trial in Germany. One of the squaddies - despite the abundance of trees he could have aimed at - had a pee against the side of his APC, at which point his NCO gave him a good talking-to, explaining in no uncertain terms that Ronny REME would check the vehicle, think it was an oil leak, dip his finger in and lick it to confirm it was oil...