I have a 2012 AT Fit with 6500 miles. I took the car to a Ford dealership to get Auto Butler applied and to have the oil changed & tires rotated. Before I took the car I would average around 30-33 MPG, now I am getting around 23-25 MPG.

I haven't been driving any differently. The only difference is the temperaure has been a lot hotter recently. I don't know much about cars other than how to drive one, but could Ford have messed something up?

 

Is the oil between min/max on the dip stick? Does the invoice say the oil was exchanged with the correct weight (i.e. 0w20) and was genuine filter used? Finally, is the tire pressure correct?

 

Have you been using the A/C lately because of the hot temperatures? That will decrease your mpg.

Are you calculating mileage manually, or are you using the mpg display? If the latter, are you resetting your trip odometer? Maybe the dealer left your car idling and lowered your cumulative mpg if you are not resetting the odometer.

Also, check your tire pressure, if they are underinflated it will reduce your mpg's as well.

 

I don't know about the oil level, but I will check that and get back to you. I also don't know what weight they used, it doesn't say on the receipt.

The tire pressure is correct in all four tires within +/- 1.

I have been using the air conditioner since I got the car, even in the winter so I don't think it could be that? I definitely haven't been using it any more than usual. I always have it set on 2. I like to be cold.

When I fill up I will reset the mileage. When I refuel, I will take the mileage and divide it by how many gallons I filled up with. I don't use the display since it never is correct. I tend to refuel when I have reached about half a tank. Usually this is around 160 miles and 5 gallons of gas.

 

I called the dealership and they use 5w20. Should I take it to a Honda dealership and get the oil changed again?

I checked the oil and the level is about 1/2" above the top level.

 

too much oil. I doubt that would have an effect on fuel consumption (it could, or worse) but I'd have them drain it to the right level at the very least. They probably didn't look up how much oil a Fit holds with a filter change (3.8 quarts) and overfilled. 5w20 or 0w20 doesn't matter much. If you obsess about oil, Honda uses synthetic which has better protection qualities than conventional mineral oil, but they'll charge about $50 for an oil change.

It's probably a change in driving pattern that you don't perceive that has caused your drop in mpg, but if you're going to obsess about it, take it to the honda place and have them redo the oil change. It's cheap therapy. And really, a Ford dealer for service? tsk tsk.

Oh, and the computer is accurate within 1MPG +/-, more so than calculating from a single fill-up (the pumps at different stations have different shut-off tolerances; and never ever top off).

 

First thought is Ford dealer used too high viscosity oil; typically 10W-30 or even 20W- 50 so the engine works a lot harder and hotter. Thus 25% drop in mpg. If you got a receipt see if the oil is identified. Like most Detroit dealers they ain't too inclined to tend well to Asian cars. Next time I'd find a good independent oil change house if I couldn't do it myself. And next time specify in writing you want: 0W-20 oil. And synthetic Mobil 1, Castrol, etc. No cheap ID oil. Or filter either.
You might want to check the filter they used, too; many of the sftermarket filters aren't low pressure drop filters needed for many modern engines. Cheap is cheap on purpose.
BTW don't count on driving more than 3000 m iles before you change oil again - and to the right stuff. Good luck.
PS they did change the filter, didn't they?
And whats autoButler? some kind of thing that notifies you need to change oil? Thats standard on a Fit and about as accurate.

 

Ford uses a 5w20 and has been for longer than Honda. Oil is not the problem unless its over full but they should of checked that before giving the car back.

 

Really?891

 

Yea thats partly true, not sure about 25% but thicker oil def does consume more power / fuel to operate, picture yourself running in water vs land. Resistance is futile.

 

Power consumed is easily found on dynos; not aware that Ford has been specifying 0W-20 oil at all, much less longer than Honda. Last time I was with Ford - yes over a decade ago - it was 10W-30.
Its not just the power to pump the oil, its also the less lubrication because of the thinnerr oil seeping into tiny clearances. Most Mascar teams use very light oil for qualifying for the same reason. It gets replaced before race time.

 

It's on the order of 2.5% (page 2-3). Within a reasonable margin of error with other variables at play, so not really detectable unless you're tracking fleet averages. On a Fit, 2.5% is less than 1mpg. If 25% better fuel economy could be achieved by dropping oil viscosity a grade or two, people would be shouting it from the hilltops. Mahout knows better.

 

The head loss for pumping oils in small orifices is usually represented by f L vsq divided by 2 g d where f is a friction factor, L is length of flow path, v sq is the velocity squared and g is acceleration of gravity, and d is the flow diameter.
All things equal as to the oil and temperature f doubles when the Kinematic viscosity doubles from 65 to 108 centistokes, which is about the change from 10 weight to 30 weight motor oil.
Thats a lot more than 2.5%. if all you gained from 0W-20 from 10W-30 was 2.5% there's no need to use less viscose oils for reduced power consumption. The 2.5 % gets lost in just mechanical friction losses.
Until synthetics came along with their vastly better shear strength lighter oils was virtually impossible for engine lubrication but it didn't keep racers from trying.
And blowing engines.
PS they are shouting from the rooftops in tech circles, like SAE.
While the increase in pumping losses from 3 to 10 hp doesn't matter much at 700 hp ifrom 1 to 3 hp matters a lot at the 10-20 hp typical power required to get a vehicle down the road at 60 mph.

 

Check the link I posted. (here it is again) 2.5% is high. 25% is ridiculous.

Here's the relevant bit:

 

read it again. Doesn't match our testing results, however, they also modified the oils with a Moly friction modifier which we didn't. I'm concerned that the MoS reduced the difference in viscosity but since they didn't publish their data its hard to compare them. Anytime you compare pumping oils without the attendant viscosity measurements the results are incomplete. Still, both Honda and Toyota specifically recommend low viscosity oils and since the only ones thatmeet their specs they are depending on synthetics which we also have found to be much superior to conventional hydocarbon oils in lubrication applications.
I wonder if their oils were BOTH synthetics or BOTH conventional oils, either of which could have reduced the FE diffence to the 1.5 to 3.5% FE change they repoprt.
From our tests we found the differences between conventional hydrocarbon oils and synthetic based oils. we found often that the reported viscosity grades were not the same as the measured viscosities.

 

Last I checked, 0W20 was only available as synthetic. They make a point of noting the cost of this oil so I suspect the other was conventional (this was 2001).

25% change in fuel efficiency by changing oil grades is ridiculous, synthetic to synthetic or conventional to synthetic.

 

It's doubtful that it's the oil level. I dumped 4qts into my fit last oil change (what am i going to do with the last .2qts) and it ends up a good 2 inches over the full mark. MPG is just fine as compared to when i obsessively tried to hit the mark.

how long have you been observing the problem? Is this the 1st tank back from the service or several tanks now?

The first guess is that it's just a intermittent issue that will solve itself refill. (maybe they were idling your car, or bad gas or something).

If the problem persists, my opinion is the problem is going to be a coincidence or something you can't guess. Like if they bumped your alignment or your brake pads are dragging or something like that.

 

Was at my Honda dealer last week and they had Honda Dino oil 0w-20 for sale along with synthetic.

 

I use my AC religiously and as long as I spend 50% of my miles on the highway I average north of 30mpg, even with idling for 20 minutes each morning before my formations (military)

Check your tire pressure. Check for unusual tire wear

Honda wants 32 psi in the tires (BASE model 15" steelies for me) and the factory Dunlops say 44psi MAX on the sidewall

I run 36psi driver front, 36.5 psi pass front, and 34psi in both rears

Makes the car slightly more twitchy, but better gasmileage. I am going to go to 37 or 38psi up front next time I rotate tires and to 35-36 psi in rear

 

I had this 1991 Taurus SHO (Pretty fast car actually) and I experimented with different oils and weights. I keep track of my gas mileage on every tank and I really did not notice a difference at all in terms of mpg. It's not the oil that is for sure. As long as your tire presures are good (You have a tpms sensor) not really sure what else it would be. You don't have a CEL so nothing is broken. Hot temperatures will effect gas mileage, the air is now thinner and lighter so that could account for some of it. You could hook it up to a smog machine and see what is coming out. I honestly think it's in your head. There is just nothing that would cut your gas mileage down 33% after a repair without warning light, or weird sound or something.