yes, a tonneau cove helps a little, it decreases the amount of wind drag on your tailgate, but so does taking the tailgate off or just putting it down if youre going on a long trip
The previous answer given is technically incorrect. Usually tailgate down you increase the drag on a truck and will get worse mileage. A cover will actually improve you mileage a little but the weight of the cover may negate a portion of this. There are several studies cited online for this. Most places that talk about lowering the gate aren't basing it on science but on what they think is logical. Aerodynamics isn't about logic, it is a very complex science. Mythbusters actually tested this out, do a search on it.
The benefits of having a hard tonneau cover on a pick up truck is that it increases gas mileage as well as an increase of security of your personal goods. Another benefit is better protection from harsh weather conditions.
This depends on whether or not you are using a bed cover. If you are using a bed cover, you can greatly increase the storage capacity of a vehicle. Find a truck's bed size to determine which has the largest bed, and go from there.
It's on the valve cover
It is in the valve cover.
It depends on the insurance.
smack in the middle of the valve cover
the miles driven to and from a destination approved by your job/company
The question was asked about pickup covers, not the pickguard, and the answer is, no, the plastic covers that go over the pickups aren't necessary, they are cosmetic, but it would sure look ugly without them.
bease the forest cover ivaesw
Mine's in the Right Side front Valve Cover
follow the top radiator hose to the intake, its inside the cover.
it is on the valve cover, usually in the driver side valve cover. If you have a 2.2 L engine, it doesn't have a serviceable PCV valve, it is built into the valve cover.