Can a self employed long haul trucker use the standard mileage rate for my leased truck or do I have to use actual expenses?

I was told I had to use actual expenses for a semi truck that was leased but I can't find that information anywhere.  When I tried actual expenses it only gave me a credit of $406.00 for 90K in expenses.  When I ran it on mileage it gave me a 62K credit.  Something is wrong.  Thanks