that could most certainly be the case .... I had a 1978 Jeep J10 pickup with a 360 cc engine mated to a 4 speed floor shift that I literally kept for 24 years .... during that time we rebuilt the motor twice .... she would get about 10 mpg .... I need to get some miles on our new truck prior to towing our 5er, so tonight after eating I took her out on a 35 mile drive .... most of it was over a narrow, rolling 55 mph state road with some 70 mph driving on I-40 thrown in .... per calculations by the trucks odometer system she got 15.3 mpg .... I'm happy with that .... within the next week or so we intend to install a bed cover, it will be interesting to see if it has any impact on the truck's gas mileage