About three weeks ago I took my 07 H3 (17000 miles) into the GM dealership for service. I had them change the oil to Mobil 1 synthetic, balance / rotate tires, and fill up the tires up with nitrogen. My question is since the service was done, i have noticed my MPG has dropped fairly drastically from approximately 350 miles per tank to approximately 300-320 miles per tank. I have also noticed that there is a sort of thumping sound coming from my front wheel (feels like it is now unbalanced). Anyways, just curious to see what the issue could be and any advice would be appreciated. Thanks!

 

the wheel not being balanced or aligned would throw your mpgs off... have them check it out, could be the wheel bearing is shot... 350... must be nice, Im babying the pedal on mine and getting about 250

 

DAGKANA, did you get your speedo recalibrated? You might be getting better mileage than you think. Take a look at my post I put up today