Small Gas Tank Issue

I have a 2000 Rodeo. I have owned it for a year and have never questioned the fact that I have to fill it up every 3 days, and at most only putting 6 to 10 gals in, thus making me think it has a 10 gal tank. I was doing some research and found that standard tank size is 21 gals. I called dealership and they told me it only lists a 21 gal tank for Rodeos. Is this right? Has anyone ever had this problem? I guess I will keep a can of gas in the back of the Rodeo because I am going to run it out completely before filling it again to see if this is correct. Please, any comments would be appreciated.

It is definitely a 21.1 gallon tank. Search for 'fuel sending unit' in this forum for possible cause.

Yeap, 21.9 gallon tank - should get nothing less then 340-360 miles to a tank, city mileage as long as it's in the 15-16mpg average.

Fuel sending unit sounds like the culprit, and I bet your fuel gauge never registers full either?

No it registers full, but it has always worked fine. I have driven this for over a year and nothing seemed to be wrong at all. The only thing is having to stop every 170 - 200 miles and get gas. Never thinking it could be anything other than a small tank.