Previously, Hennessey operated as a vehicle tuner since 1991, specializing in Dodge Vipers initially before branching out to cover a wide range ... production car to ever feature a manual ...
In our tests, we've found that in some cars a manual transmission can improve gas mileage by a significant 2 to 5 mpg, compared with an automatic, and can cut a car's price by $800 to $1,200.