Is it true that some propane exchange compaines dont fill the tanks all the way to make more money?

I recently wanted to exchange my propane tank and noticed it felt lite. the lable read 15 lbs not 17 lbs like my tank label. It took me driving around to a few gas station where I eventually found that Lava propane exchange fills to 17 lbs.Is it true that some propane exchange compaines dont fill the tanks all the way to make more money?
Propane cylinders are filled by weight. On the collar of the cylinder is a marking stating the water capacity. We fill the cylinder to 42% of that number. Propane is half the weight of water, so that equates to about 84% full. This allows room for the liquid to ';grow'; if the temperature of the cylinder rises. This number can vary by as much as a pound on a 20lb cylinder. also the tare weight, which is the weight of the cylinder with nothing in it can vary by as much as two pounds on a 20lb cylinder. So not every cylinder will weigh exactly the same when you pick it up. More than likely that is just a cylinder that was at the lower limits of the acceptable range for these tolerances.





It certainly isn't impossible for them to be under filling the odd cylinder, but it was probably unintentional. I would return it to the point of purchase and ask for someone to check the weight of that cylinder and give you a reasonable explanation...





It likely wasn't done to make more money, but in the interest of safety.