The older Mazda3's, like my 2012, had a 14.5 gallon gas tank volume. The newer models are 13.2 gallons. That is an unfortunate drop in volume. I drive a lot and don't like going to the gas station 3-4 times a month.
Has anyone ever changed out their gas tank volume for a bigger volume?
IMHO, If we look this in terms of cost , it will be a lot cheaper for you to spend every month the price of 6gallons than to change the entire gas tank volume, even if it would be possible (which it might be or might not be).