The valve device consists, according to the invention, of (at least) two part valves which are symmetrical in circuit terms with respect to the existing connections and which are designed, in particular, as four-way, two position valves of any desired type of construction, but preferably are provided as slide valves. There is preferably a double slide valve with two cooperating slide valves. The valve device features internal seals and sealing surfaces which minimize wear and damage to the seals as they move across flow ports. The valve device is particularly adapted for use as a fuel control valve for an internal combustion powered motor vehicle having two separate fuel tanks. The valve device permits control over which tank supplies fuel to the engine, and allows controlled mixing of the fuels from each tank.