High Gas Consumption in city driving!

[Bedford007]

A year ago, my 2010 Genesis sedan 3.8L, went from a nice 10L/100Km to 14L/100Km. I had a dealer look into it and $2500 later ended up with problem not resolved. The dealers approach was hit and miss approach:
- Lets replace the spark plus
- Lets replace fuel injectors
- lets replace the Mass Air Flow Sensor

All of the above did nothing to rectify the problem. I did give a piece of my mind to the dealer in that they should be brain storming the problem and not trial and error approach which in essence is a money grab.

Anyone else experience this type of increase in gas consumption?

 

[Gunkk]

So 23mpg to 17mpg in the city. 23 seems high for city, but 17 doesn't seem all that low even for a V6. I get 18 in my 4.6 most tanks, but if I get heavy with my right foot it can easily be 14-15.

So the dealer fired the Parts Cannon, eh?

How many miles on the car?

Q&A time... Diagnostics:
CEL on? ...which codes?
Did they do a compression test?
Replace fuel filter or air filter?
What about O2 sensors?
What does the long term fuel trim show? If it's heavy-rich, then it's throwing extra fuel at a what the ECU sensed to be a lean condition. Most often caused by intake manifold fuel leak or dirty/bad throttle plate or throttle controller. Did they bother to check any of this? If the LTFT is close to zero (less than +/-5%) then the problem not likely MAF or intake, but you never know because sometimes a dealer can unknowingly replace a bad MAF with another bad MAF.... it happens.

Fuel:
Same time of year? Same part of the country? Did the fuel regulations change driving a change in fuel formulation? (summer/winter fuels in the USA often affect mileage).

Tires:
Did you change them? +/-10% is possible depending on rolling resistance.




Pro tip: you can log the LTFT or watch in real time yourself with Torque Pro App for $5 plus a $15 bluetooth OBD2 reader.

 

[Bedford007]

So 23mpg to 17mpg in the city. 23 seems high for city, but 17 doesn't seem all that low even for a V6. I get 18 in my 4.6 most tanks, but if I get heavy with my right foot it can easily be 14-15.

So the dealer fired the Parts Cannon, eh?

How many miles on the car?

Q&A time... Diagnostics:
CEL on? ...which codes?
Did they do a compression test?
Replace fuel filter or air filter?
What about O2 sensors?
What does the long term fuel trim show? If it's heavy-rich, then it's throwing extra fuel at a what the ECU sensed to be a lean condition. Most often caused by intake manifold fuel leak or dirty/bad throttle plate or throttle controller. Did they bother to check any of this? If the LTFT is close to zero (less than +/-5%) then the problem not likely MAF or intake, but you never know because sometimes a dealer can unknowingly replace a bad MAF with another bad MAF.... it happens.

Fuel:
Same time of year? Same part of the country? Did the fuel regulations change driving a change in fuel formulation? (summer/winter fuels in the USA often affect mileage).

Tires:
Did you change them? +/-10% is possible depending on rolling resistance.




Pro tip: you can log the LTFT or watch in real time yourself with Torque Pro App for $5 plus a $15 bluetooth OBD2 reader.

You are little too technical for me.
No compression test.
Changed tires from winter to summer - no change
Fuel and air filter replaced. (BTW: high manufested after air filter replaced, that is why I thought it could be MAF)
Same time of year (Fall)
CEL, LTFT ... all too technical

I had a friend hook up his laptop to ODB port while I drove; and he said all seems to be OK at low and high speeds.

 

[Gunkk]

You are little too technical for me.
No compression test.
Changed tires from winter to summer - no change
Fuel and air filter replaced. (BTW: high manufested after air filter replaced, that is why I thought it could be MAF)
Same time of year (Fall)
CEL, LTFT ... all too technical

I had a friend hook up his laptop to ODB port while I drove; and he said all seems to be OK at low and high speeds.

Read this:
Fuel trim: How it works and how to make it work for you - Automotive Service Professional