[Red3722]

My boyfriend has 2006 1700 roadstar silverado that for a while now has been burning gas a lot. Other day he pulled the dipstick and oil was backing out profusely. The oil got changed yesterday and it was real thin and a lot of it it smelled like gas what is the cause and how do we go about fixing it

 

[Easy Rider]

If it has carbs, a float is stuck or the needle valve is stuck open, allowing gas to "overflow" the carb and run down the throat and into a piston where it leaks past the rings into the crankcase.
Inspecting the plugs should tell you which one is wet with gas.

 

[Aussie Steve]

If this is the cause fix that and then I would do an oil change twice to flush any fuel out of the engine.