Meek Mill -- Car Dealer Demanding $250k For Instagram Diss

Meek Mill has driven his car dealer mad ... mad enough to sic his lawyers on him and demand $250k for slamming his business.

According to the demand letter sent out by Euro Motor Sport, Inc. in Fort Lauderdale ... Meek wreaked havoc on his biz with an Instagram last week. The post showed a sweet Lambo Aventador, but included the caption, "Make sure you never buy no cars from #eurosports selling expensive cars with salvaged tittles."

Grammar and spelling aside ... the dealer says Meek's IG post is ruining its reputation -- especially with celebrity clients. They point out Rick Ross even reposted Meek's message.

According to Euro Sports owner Gene Morales the beef started when Meek's manager went to pick up a Rolls Royce Ghost ... but still owed $15k on the $200k whip. Things got heated when Morales refused to hand over the keys without payment, and he ended up calling cops.

Cooler heads prevailed though when Morales struck a deal ... agreeing to hand off the car for a mere $8,000. You'd think Meek would have been happy, but he still bitched on IG.

Now, Morales wants the quarter of a million bucks to cover the damage to his rep, and he wants Meek to delete the Instagram and apologize. If not ... Meek could be facing his second lawsuit in recent days.