Went from 53 mpg to 46 mpg in 7 weeks

Have you put any air in the tires since you got it? I went to 42/40 in late July and found the pressure had dropped ~3-4 psig on all four corners by last night. About half of this is because of lower temperatures, the other half is normal air loss.

 

Could be the brakes hanging on you.
Could be your alignment has gone wonky.
Could be the ethanol in the gas (changed stations? check the pump for stickers).
Tire pressure, as Shawn says, is also something to check.
You aren't driving in B mode, are you?

 

That's fairly low on the Integrities. It sounds like they had you set at the door placard pressures or thereabouts. Mine started out a few pounds over from the dealer (one of the rear pressures was higher than the front.) I reset the pressures myself.

46 mpg is still very good with such a low tire pressure.

 

As the outside temperature lowers so does your tire pressure. At 32/33 you are below the recommended pressure on the sticker in the door. If I were you I would pump up to about 38 all around and see how that goes. Also remember that tire pressure is only accurate if you check it on cold tires that haven't been driven on in at least 3 hours or more.

 

Hi hypno...,

Your response to the comment seems to imply tire pressure does not change once set. Which is incorrect. Besides the temperature effects - about 1 PSI per 10 degree F change, there is leakage. Its best to get one of these portable battery pack / air pumps. Go out the car on Saturday or Sunday morning before the sun hits the tires, and check the tire pressure. 42/40 psi as was commented on works quite well.

This is at least 50 % the cause of your mileage reduction, if not more.

Additionally, warm humid air is less dense and creates less aerodynamc drag. If your doing allot of your driving above 45 mph, the weather variations in the past few weeks will certainly have a big impact. Its been down in the 40s up there in WI I imagine? As its been in the low 50s here in the past two weeks. If your driving in the morning during this cool weather, and fast , that would account for the rest of the mileage reduction.

Driving in rain is a big impact in mileage too. Besides the stop-and-go traffic rain causes, the rain will cool the radiator, and the engine thermostat will open up further to keep the block at proper running temperature, which uses more gas. Rain also has more mass than air, so pushing it out of the way requires more gas. Water on the road sticks to the tires for a small distance at the tire rotates, and then falls off. This lifting of the water requires more gas. Tire treads push water aside to avoid hydroplaning. This pumping action requires more gas. Driving home in the Hurricane Gustav remnant had big impact on my mileage.

 

Was happening to me all the time ! Even after break-in.

CULPRIT - gas additives, like Ethanol, but not necessarily advertised as such.

In Canada, was almost always getting gas from Petro Canada, and was always stuck at 5.4l / 100km or 5.6l / 100km.

Now I'm always using pure Regular, like from Shell, and EXACT same conditions, I'm getting 4.2 to 4.6l / 100km.

If I get a sunny week, I get 4.2...a rainy week will be 4.6.

I don't drive much above 100kph (60 MPH).

 

Are you maybe making more short trips? That's a MPG killer.

More stop-and-go driving or hitting more red lights?

You could also reset the MPG on the display and then go for a 20 mile relaxed drive at a sustained 55 MPH and check what the MPG is then.

 

Something is drastically wrong! You should easily be averaging 60-80 mpg, no matter what the conditions; uphill, 6 people in the car, AC blasting at high continuously, and even with low tire pressure. I'd take it back and complain. Maybe you got a lemon.

 

Please see my thread entitled, "After Service Issue". I have experienced the same problem since June.

 

Most likely there's not enough air in the tires. Tire pressures should be checked and adjusted at least monthly; do it when the tires are cold.

Using 42/40 makes it easier to get better MPGs, but the ride is harder. Try it and see what you think. If you do this it will also be necessary to check the pressures after the car is serviced at a dealer, 'cause dealer techs love to re-set them to the factory value.