While rules are different in each state - normally states provide Fuel tax refunds if the fuel was used for a non-highway purpose, such as lawnmowers, boats, bulldozers, combines, non-highway logging equipment, etc.
If the fuel was use by trucks on the road - you may not claim fuel tax refunds.
see for instance
WA - http://www.dol.wa.gov/vehicleregistration/ftrefunds.html
FL - http://dor.myflorida.com/dor/forms/download/!refunds.html
MO - http://dor.mo.gov/tax/business/fuel/forms/
WI - http://www.revenue.wi.gov/forms/excise/index-f.html