A few years ago, we were going from palm springs to yuma & took a back road ( county S30 ) as a shortcut & bypass around El Centro. This is in the middle of farm country. Lo & behold about half way to I-8 we were stopped by some? government men in a fuel check roadblock. I don't remember what agency set up the roadblock & the strange thing was this was basically a rural farm road & we didn't see any other rv'ers while we were on it. They were checking vehicles travelling north & south & I suspected they were looking for locals who might be cheating with red fuel ( gas or diesel ). My dad told me a story about gas rationing during WW2. He owned a garage at the time & claimed people were filtering the dyed gas through homemade bread & that took the red out of it? YMMV.