I have two answers.
First- an eternity assuming you don't have any tools and need to carry tiny bits of dirt by hand to the truck. This would take your entire life and not be completed.
Second- First verify some points:
1 week
The average miles per gallon for a 24 Ford diesel box truck is 11 miles per gallon. The miles per gallon is dependent upon the driving conditions and the driver.
That would depend on the average speed. If the average is 50 mph, they drove 650 miles.
The average box truck miles per gallon is dependent upon the size of the box truck, the size of the engine, and the driving conditions. Most box trucks will get around 10 miles per gallon.
50,000 miles, usually average is 12,000 miles a year.
The average mileage for a year's worth of driving for an over the road trucker is about 156,000 miles. That is an average of about 3,000 miles per week.
3,000 somthing like that
The amount of gas mileage that you can get from a 2011 Toyota truck can be anywhere between 14 and 30 miles per gallon of gas that you purchase. The average of that would be about 20 miles per gallon.
If that's really what the question is, the answer is 1400 mph. If the question is actually "A truck travels 1400 miles in 20 hours, what is its average speed?" then the answer is 70 mph.
It really depends on the engine. For that reason, the average gas mileage for the average pickup truck is anywhere from 13 to 20 miles a gallon. So, to attach a definite number on it, it's probably hitting around 15 or 16 miles to the gallon.
The 2014 Toyota RAV4 EV is the highest MPG truck. It is an electric hybrid and gets an average of 76 miles per gallon.
A Peterbilt Super Truck manages to obtain an average of 9.9 miles per gallon. Most modern day trucks average 5.5 to 6.5 miles per gallon. With this 54-percent increase in fuel efficiency, this will save thousands of dollars a year for the long-haul truck drivers.
A used work truck is better if it has lower than average mileage as long as it is in better than average condition. If it is not in better than average condition it was probably not well taken care of and not worth the expense.