A Warning For Everyone
Please warn everyone that owns any manor of Diesel or Gasoline fueled vehicle or machinery to not fill the fuel tank more than about 90% full. Diesel fuel and gasoline expand as temperature rises and contracts as temperature falls. Only the air above the fuel can compress or expand. You are very correct that when the nozzle trips to STOP right there. No more fuel should be added. The same holds very true for fuel in any tank or storage container. I’m sure you have seen the tuff plastic gasoline cans. Guess what? They are air tight and if you fill one up too full and then place it where sunlight heat strike the container it’s KABOOM time soon thereafter. Yes it will bust open and with force. On the other hand if you put the same into a freezer or place ice around it you will see it contract. The lesson is to not fill it above the full mark and especially if there will be temperature swings. People tend to overfill their lawnmowers only to have fuel spit from the cap vents but anymore thanks to bad EPA laws the caps and thus the tanks aren’t vented. In a really bad case the tank may bust apart and the hot engine gets covered with gasoline. BAD NEWS for sure. With an automobile or truck the fuel line may bust, fuel filter rupture, tank split or the engine may really get flooded with good much fuel. All of the above are very bad. We need to remember the temperature of fuel down in underground storage tanks is very different from the temperature outside above ground and especially in the summer.
Checking fluid levels (other than fuel mostly) when they are hot isn’t the right way unless you suspect problems. Please check them after the engine has been stopped for several hours or longer and be sure the vehicle / machine is on good level ground. Don’t overfill but do keep them close to the full mark / line at all times.