Assumption of 15k a yr driven 8k being regular driving 7k being towing using my local fuel cost:
GAS Truck
Cost 45k + tax = $47700
$47700 @ 3% for 60 months is $857
Fuel Cost: 2.89 a gallon regular
8k @ 16mpg = $1445
7k @ 6.9mpg = $2931
Total of $4376/year in regular gasoline cost @ 2.89 per gallon
Cost to own per month is $1222
DIESEL Truck
Cost 55k + tax = $58300
$58300 @ 3% for 60 months is $1048
Fuel Cost: 3.69 a gallon Diesel Fuel
8k @ 19.9mpg = $1484
7k @ 10mpg = $2583
Total of $4067/year in Diesel cost @ 3.69 per gallon
Cost to own per month is $1387
Monthly Cost to own Diesel truck per month payment and fuel = $1387
Monthly Cost to own Gas truck per month payment and fuel = $1222
Difference of $165 per month for 1st 5 years to own a Diesel over Gasoline...
After the 5 years of payments is up the cost to own difference is $309 in favor of the Diesel truck but none of these numbers include maintenance or reliability factor at all just payment and fuel cost...