Many truckers believe the Cascadia gets the best mpg. I hear truckers say they get about 7 mpg on the open road with them.
http://www.freightlinertrucks.com/trucks/find-by-model/cascadia/default.aspx
There hasn't really been a brand of semi trucks recognized as the most fuel efficient. Since they run on diesel a more efficient fuel, semi trucks already are more fuel efficient than cars in terms of size and power.
Right now, it seems like a toss up between the Volvo I-Shift and the Allison TC10.
No. Recent advance in technology do not require idling of a semi.
The average fuel economy of a semi truck is between 5 and 7 mpg when loaded.
According to the Elmo Kandel, Editor and Publisher of Article Click, a highly efficient semi-truck will get 6 to 8 miles per gallon. Fuel mileage will vary greatly based on the weight of the truck and payload and environmental factors such as wind and grade. Fuel mieage can drop to 4 miles per gallon in less efficient trucks - you need to go to www.fairtran.com to find out more.
A fuel pump siphons the fuel through hoses.
4-8mpg of diesel depending on the year, condition, and modifications to the truck.
No manufacturer claims their truck to be the most fuel efficient, because there are too many factors affecting this. Such claims are made in regards to the engines, but not to the trucks themselves. Detroit Diesel motors have been traditionally known for their fuel efficiency. Volvo makes a similar claim with their D series motors, although they only seem to live up to those expectations solely under ideal conditions.
The truck has the most mass, but because it is at rest, the skateboard has the most momentum.
You don't. The fuel system draws from both tanks concurrently.
a moving semi-truck
The MPG a truck gets is going to depend on a number of factors, such as the drivetrain, weight, terrain, etc. Another important factor which affects the mileage a vehicle gets is how its driven, as well as the type of trailer you're pulling - a regular van trailer can be made quite aerodynamic in conjunction with a tractor, but trailers such as flatbeds and their loads typically don't create ideal aerodynamics. AFAIK, no manufacturer claims their truck to be the most fuel efficient on the road, although they do place emphasis on features which can make a truck more fuel efficient, such as lighter weight, aerodynamic design, etc.