Lower MPG

[supton]

Check tires, check brakes. Maybe check alignment. But 2 mpg is like a 6% drop in mpg. I wouldn't spend too much money trying to fix, it's not a big drop.

 

[WyrTwister]

Originally Posted by borgward
2013 Fiesta SE Hatch Manual Trans 1.6 Liter Engine 55,000 miles. Bought brand new. The odometer has consistently reported 37 MPG overall mileage until lately. It is now showing 35 MPG overall MPG for the last several months. Seems a little early for spark plugs. No fuel in the oil. Hardly measurable oil usage between oil changes that I do my self. Mobil 1 From the first time I changed oil. Next oil change is due in several hundred miles. Oil analysis always come back very good. I plan to check the compression at next oil change.

I do suspect gasoline quality is heading south in Texas (Shell Regular) - I drove up to Kansas and out west to the Pacific coast last year. Car ran better on gas once I was going west. Even in California. As I entered Texas on the way back I got less pep and poorer MPG.

Anything else I should check?


Amount of ethanol in the gas , in those other states . Texas allows 10% , unless stated otherwise .

Check the air box / filter . Both for a dirty filter and for foreign objects ( rodent nests ) .

Is the transmission shifting as it always has . Emergency brake " free " . Other brakes dragging . I try to run 40 psi tire pressure . Any codes ?

Best of luck to you ,

 

[Burt]

I have a 1.0 liter ecoboost Fiesta. For years, I was getting mostly 37 mpg mostly around town. It dropped to 34 partly because I got new tires. It's an RV tow vehicle, aka a dinghy, so the tires have more miles than odometer registers. I know that new tires have larger circumference, the increased tread depth results in squishiness and the original tires were low rolling resistance and the replacement not, but seemed like a larger than expected difference.

I have only 32k miles on it but suspect carbon build up.

 

[circuitsmith]

Check coolant temp with an OBD scanner.
Could be a tired thermostat making it run cool.

 

[DGXR]

2mpg (5%) difference is not significant, not enough to be concerned. Give it a year and report back. If it drops significantly, then you have a problem.

 

[Redright9]

I love and hate these "gadgets" new cars have. I love all the information, but hate it because I overthink it. Many of these readouts arent overly accurate. and like DGXR states, a 5% difference is almost too small to worry about. It could be a variety of items such as what has been listed here. That readout is just an estimate from the other items the computer has to guess the MPG, kind of like the miles to empty. Every so ofthen, do the actual math and that will give you a better indication if you are having a drop in MPG. New cars are sensitive, if the car was having an issue, most likely a check engine light would be on.

 

[borgward]

Did the actual math from day one. That 5% is in the ball park for overall MPG. That read out was a nice heads up. I do not take anything for granted. For over 5 years the 5MPG was around 37. In the last 2 months the overall average has gone down to 35. That means that the average fill up in the last 2 months have had to be way lower than 35MPG to bring the 6 year average down from 37 to 35 MPG. I am getting 28, 27 MPG between fill ups a lot of times now. That off way off from just 5%.

 

[brages]

My MPG varies a lot with my average speed -- low average speed means lots of traffic and I get bad mileage in traffic...

 

[borgward]

The driving variables have not changed very much, so that's not it. In other words the mix of highway and traffic mileage is pretty much the same. Everybody knows you're going to get less in stop and go traffic. Well unless you have a hybrid. I understand they do better in stop and go than on the hwy.

 

[The_Nuke]

I have found my MPGs drop at least 3 for any tank in which I exceed 120MPH more than twice, even if for a few seconds.

Perhaps there have been more than usual number of passing maneuvers executed per tank of fuel??

 

[borgward]

I quote myself "The driving variables have not changed very much, so that's not it. In other words the mix of highway and traffic mileage is pretty much the same" Well that goes for speeds as well.

 

[borgward]

Getting close to doing the oil change when I will also check spark plugs, etc. I am also shopping for a gasohol text kit to see how much alcohol is in the fuel I am buying. can anyone recommend a good one?

T

 

[HangFire]

Good ideas here, I don't think Engine Air Filter was mentioned.

 

[The_Nuke]

 

[borgward]

Of course. That's an obvious one one.

I am about ready to run down through all the suggestions and make a to do check list.

 

[borgward]

Did the oil change today at 6000 mile interval. Started on list of suggestions:

Check the scale???

Try a fuel system cleaner such as Amsoil additive, or techron....and bump it up a grade while running it

clutch slipping?

maybe carbon buildup?

sticking brake caliper or bad wheel bearing?

Have alignment checked

Weak battery needing more from your alternator.

Amount of ethanol in the gas

Check the air box / filter

Check coolant temp with an OBD scanner.
Could be a tired thermostat making it run cool.


Don't think the clutch is slipping. I can start up a hill and punch the throttle and not produce any slippage. That would be obvious. Checked the air filter. Looked almost pristine. Could not shake more than a tiny bit of dust out of it. The airbox it is in has no restrictions, mice, etc. I am wondering how to assess the battery. Seems OK. Engine starts with only a bump of the key. There's no ammeter on this car. I do have a VOM. Would OBD display anything about battery health? Brake pads do not seem to be dragging. Will check coolant temperature tomorrow with OBD reader. The temperature gauge on the dash shows the engine warms up within several miles to where the needle has always stayed.

Will pull the sparkplugs and look into the cylinders for carbon after the Motorcraft wireset comes in.