I have a 08 HCH with 145K miles and I'm only getting 20 to 28 MPG's. I have my IMA battery replace from the dealer at 125K miles. I just replaced my spark plugs at130K miles. I have Goodyear fuel max tires with good thread @ 38PSI. I just got my Trans drained and filled as well.The only maintenance I haven't done is adjust my valves. What do you guys recommend I do???

 

Is this a new development? What mileage did you get right after the battery was replaced?

Is your battery recalibrating? Shows 6-8 bars, then rapidly drops to 2 bars at about 1 bar/second, then force charges with no assist? After that it may either start to behave normally once it hits 3 bars OR, it will stay near 3 bars and then go to full at 1 bar per second.

What are your driving conditions? speed, terrain, traffic, etc.?

A/C use?

 

You can almost rule the battery out with that low of mileage. Even with no battery at all, you should get 40MPG highway and about 30 City.

Check your tire pressure. Should be at least 38PSI per tire.

clean throttle body and make sure air filter is good.

remove all extra weight/items from trunk and back/front seats

make sure wheels spin freely (check brakes)