I don't put any weight in the bed and I don't have any problems.

 

Ive never put any weight in my bed and never had a problem. But I know 2 people with 2wd trucks that put weight in their beds and do pretty good in the snow and sand.

 

I throw sandbags in the bed every year. With a 2wd it helps a lot with traction. Also just wanted to add another factor that will determine fuel economy is width of the tires. Skinnier tires are better in snow and will get better fuel economy. They are worse in mud though as far as traction goes.