It's going to depend on route and mileage of the vehicle, laden. I tend to think that it's normal to split the gas 50/50. My advice is to do it every time you get gas, rather than one on the way out and the other on the way back.
The Lady with a Lamprey
"The powerful are exploiting people, art and ideas, and this leads to us plebes debating how to best ration ice.
Man, no wonder they always win....." Lonesomebri
Get a Taint, you pathetic cur!