Not sure where you are from... Most states have lemon laws, and dealers HATE to hear about threats to invoke lemon laws. I've also successfully parked a vehicle in front of a business with a large sign or two on it... Just make sure it has a disclaimer on it! Something like "I feel like I bought a lemon" (notice the "feel" - "think" works, as does "ask me why" or "before you buy" ) with an arrow pointing towards the offending dealership. I think they owe you a new vehicle.

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Bill Streep
San Antonio
'57 190SL (toy)
'08 S5500 (mine)
'09 CLK550 (wife's)
'06 SLK350 (daughter's)
'11 GLK350 (daughter's)
'03 CLK310 (spare)