Need opinion. Took my new 2650b in to dealer for basic 100 hour service. (wanted dealer to do first servicing). Recently I did routine check of oil at 134 hours and found the oil to be black, and 1 quart low. then checked outer air filter and found it to be black/dirty. Now suspect this highly regarded dealer charged me $400 for the 100 hour service and didn't do anything. Am I wrong to suspect this?: