From a near empty tank on level ground I can only fit 10 gallons in, the only time I've gotten over 10 is on a angle. I have a Canadian VIN VX, 1992. Maybe the US/CAN VIN VX makes a difference regardin stock fuel tank size?
I have a 94 VX and I hate the gas gauge. Stays on or near full forever, then drops like crazy, floats around by 1/4 tank every time you go around a turn or up or down a hill. I wish I had the bigger tank for additional range. I filled up today because the gauge was wandering into the red line and it only took 8 gallons. I've only had the car a couple months so I'm still getting used to it. I agree it's odd not to have the warning light.
I love the bigger tank because it basically extends my tank for another week with the way I drive. I have the same issues with my gas guage: It stays full forever, then drops fairly quickly. It will stay on full for first 200 miles, sometimes more, then takes about 150 miles to get to half tank, then takes 200 miles for final half tank. It's not exactly perfect, and the needle will "float" some between different levels, especially around left-hand curves and when going uphill. I sure wish it had a warning light, so I could determine how many gallons were left when it hits the "empty" line.