Apologies if this sounds like another owner complaining about low MPG, but I've had my 2011 Sport AT for about 2 years after buying it from the original owner. It had about 20K on it when I purchased it and it ran well and got great gas mileage (always >30mpg). A few months into ownership, I took it to a dealer in SF to do some routine maintenance (change oil and filter, transmission fluid, and rotate tires). The car hasn't been the same since. There is no CEL, but I can't get more than 23 mpg with mainly city driving in San Francisco (even while babying it) and there's also almost no throttle response when I'm in 5th gear on the freeway. The gas mileage on the freeway can be pretty good (low to mid 30s if I'm just cruising).

The low MPG is really making me sour on what should be a great car. My wife loves it, but I don't feel comfortable driving it long distances on the freeway given the issue with power on the freeway.

Any thoughts on this? It should have 1 year left of warranty and I was thinking about taking it back to that dealer, but I'm afraid they're not going to find much or just say it's fine which I know it's not.

 

Did some searching last night and some owners referenced the idle learning procedure if the ECM had been reset, but there doesn't seem like enough observations to support the increase in mileage some saw with the procedure. I'll probably do it over the weekend to see it helps at all. The ECM was definitely reset at the dealer so maybe it's possible they forgot to do this procedure before handing me back the keys?

 

If you do nothing but city driving and you have a heavy foot 23 mpg isn't a surprise. the argument you have about highway performance, i dont understand why you feel unsafe. Toyota Prius' are on the freeway and accelerate way slower. what brand of gas are you using

 

It seems logical that the service messed something up; but the services indicated are really straightforward and there's nothing there that should affect the car that drastically.

There always could be something like a sticky brake pad or soemthing.
Have you checked your tire pressures? The door panel says 33psi. The TPMS low tire light won't go on till about 25PSI, so you can be down 8psi and not even know it.
That can be enough to add drag to deaden the MPG and make it feel sluggish in this low-hp car.

It has gotten colder lately. Yesterday night it was cold enough to trigger the TPMS low light on my car; but haven't really checked the tires for about half a year.
If your tire pressure is low, I'd experiment to put your tires up to 35 or 36psi (you can always bring it back down if you don't like it).
Are the tires correct? In that if they are directional tires are they pointed the right way.

 

Try using a tank of 93 from a good company like Shell that uses detergents in their fuel to keep the injectors clean. Personally, I use 93. I not going down this road on why as i wanna keep your thread focused on your question. Keep in mind, or cars only have a tad under 11 gallons when full. The difference is like getting a McDonald's double quarter pounder value meal. Just try it, go on freeway when the traffic is light enough to maintain a steady 60-75 mph for the injectors to push fuel at a high enough pressure to clean them. Id say a 20 mile r/t (10mi going/10mi back). I'd almost guarantee a difference. Let me know if you decide on trying that out. Be sure your fuel is on E b4 doing this the 87 will dilute the good gas' strength (like adding water to sweet tea to make less sweet)

 

Or just go through 2 tanks worth. It's such a small tank that it's not like a huge experiment where you need to change your habits. 20gallons of premium is like $4 extra?

If you're thinking the injectors need help, then I'd say go all the way and use a fuel additive to help rather then relying on better additives from premium pump gas.

Be sure to get one that is high in PEA. Redline si-1 (avail from amazon) is my recommendation as a cost-effective means. With the Fit's small tank, 1/4 of a bottle per tank is more than sufficient for it to be active, so just add the redline over 4 fillups or half on 1st fillup, and 1/4, 1/4. and that will cross that maintenance off the list. Of course, if it's not the injectors there's not going to be a real difference.

 

The ECM was definitely reset at the dealer so maybe it's possible they forgot to do this procedure before handing me back the keys?

Why would you think ECM was reset? Well, unless they really wanted to mess you up. The suggestions to add cleaners probably will not change anything. If you got that drastic lower MPG then dealership guys did something wrong and may be intentionally

 

I'd take it to a different dealership, sounds like they definitely messed something up