I used to have an old Chevy pickup with dual tanks. I only filled up both of them once. After looking at the price, I never did that a second time.
Pitty the over the road guy who probably has a couple 100 gal tanks, gets around 6 mpg, and has to buy diesel which is about $4.00/gal here in NH. ($800 to fill up for the math challenged)
I have run into limited pumps for diesel too. When I first started driving the MH I didn't realize some stations had diesel nozzles for cars. It can take forever to pump seventy five gallons (roughly three quarters of a tank for me) with a mini-me nozzle not to mention the auto shutoff feature. My theory on the reason was credit limit authorization per transaction as I said when I pump seventy five gallons at four bucks per that gets to be $300 per. I also learned that if I stay around 1875 RPM I get pretty good mileage ( all things considered +- 10 mpg ) but go over that and it drops off
sharply.