When you go to a gas station, the pump should tell you how many gallons you put in, if your gas pump doesn't tell you how many gallons you put in, then you should try a differnt gas station, once you know how many gallons you put in, you take the number of miles you went, and divide it by the number of gallons, it's really very simple.
I have found that the amount of gas I can fit in the tank, bare bones, is generally a little higher than what the number which the manufacturer reports it as. In either case, at 530 miles, you are doing pretty well, whether the tank holds 10 gallons or 11 gallons. I certainly would not be unhappy with those numbers.
Ok, so I found the other source that said the Civic VX/CX is a ten gallon tank. The owners manual.
It states, and I quote:
Gas Station information
Fuel Tank Capacity:
38l (10.0 US gal, 8.4 Imp gal)
(US: DX, Si, Canadian Cars)
45l (11.9 US gal, 9.9 Imp gal)
So it seems that there are some variances between the models. That coupled with the knowledge that Honda does have two different part numbers for gas tanks between the VX/CX and the other models leads me to believe that something somewhere went terribly wrong and my VX is the only one that has a 10 gallon tank, lol. But then again that statement about Canadian cars has me a bit confused. Does it refer to Canadian assembled Civics (which most all of them are) or does it refer to Civic models sold in Canada?
probably depends on the year. bought my vx new in 94. has 10 gal tank. got 605 miles before i filled up . drove from el paso tx - san diego ca fully loaded. of coarse speed limit was 55 back then and gas was .99 gal. after 14 1/2 years with my vx still love it!
Those cars are a '92 and a '93. I think somewhere along the way I got the idea that those years had a 12 gallon tank, and then they switched to 10. Not sure, though. But I'm darn sure that my tank ('95) is 10, not 12.