Lost MPG in My Newly Aquired Focus [Q]

[DrkKnight614]

Posted via FF Mobile Well my first comment is difference in shifting. The automatic is tuned for fuel economy. Your arm and foot may not necessarily be tuned the same way. Seriously consider how you are driving and shifting the car. Check all your fluids and clean your MAF sensor. Also how many miles are on this car? Difference in tires could be a huge difference as well.

[zlmitchell]

Originally Posted by DrkKnight614

Posted via FF Mobile Well my first comment is difference in shifting. The automatic is tuned for fuel economy. Your arm and foot may not necessarily be tuned the same way. Seriously consider how you are driving and shifting the car. Check all your fluids and clean your MAF sensor. Also how many miles are on this car? Difference in tires could be a huge difference as well.

78k miles on the car. And once again its not the shifting lol, I have had standards before and had excellent mileage.

Seems like everyone is quick to jump on the "User Error" band wagon.

[iminhell]

Because it is user error, 99% of the time.

Shifting at low RPM will require more throttle input, and in turn more fuel.
Try 2 tanks shifting around 3,500rpm and see what happens.


When you mentioned the brand of tire you missed completely what I meant. Tire pressure should have been your first thought. Low pressure will absolutely drop MPG's.
Being it's later in the year you should be able to get away with running more pressure than Summer. I'd try around 35psi in all the tires, maybe a bit more if you're up to it.

[zlmitchell]

Originally Posted by iminhell

Because it is user error, 99% of the time.

Shifting at low RPM will require more throttle input, and in turn more fuel.
Try 2 tanks shifting around 3,500rpm and see what happens.


When you mentioned the brand of tire you missed completely what I meant. Tire pressure should have been your first thought. Low pressure will absolutely drop MPG's.
Being it's later in the year you should be able to get away with running more pressure than Summer. I'd try around 35psi in all the tires, maybe a bit more if you're up to it.

Tire pressure is at 36psi just like my other Focus.

Also I drove 200miles straight on the highway and got 30 MPG... No shifting involved...

[fullerp]

This is the order I'd check things.

Check tires for proper inflation.
Change oil and filters (air, oil, breather, fuel, cabin) Do them all, don't be a wussy.
Plugs.
Wires.(Mikes right, no wires. Disregard this line)
Mass air flow sensor.
(edit: EGR Valve, then DPFE Sensor http://www.focushacks.com/mod/DPFE_S...GR_Information
O2 sensor
Compression Test.
Ignition Coils.
Give it to the dealer and have them test it.

Start at the top ignore all the ones you've already done, and feel free to also do other peoples suggestions.

[mikebontoft]

grab some plugs first and see how it is. you don't need the wires because it is a COP system.

[zlmitchell]

Well i replaced the spark plugs last weekend and I've gone through about 1/2 a tank so far and its looking great. Before that plugs i calculated it at 25MPG :( and now the in car is saying 35 MPG! But i will still be doing more of what people suggested and i will calculate it by hand and post back later to tell you the results.

Going to put in a new fuel filter, oil change, and clean the MAF next.

P.S. the air filter on my model is a lifetime airfilter... WTF. cannot be changed... who designed this crap.

[sailor]

FWIW my "lifetime" filter is still OK at 85,000 miles, so it's doing what it was designed to do...

If I lived on a dirt road I'd be "bitchin" about the design - but for most users it prevents the "over maintenance" that can cause more damage then not changing it....

(letting dirt into the intake tract when changing filters can be a problem, they usually get changed when they FIRST look dirty - long before any restriction..)

[emsvitil]

Swap the tires between the cars and see if the bad mileage goes with the tires.

[mac.mogul]

Yeah that lifetime filter should see you well into 150k miles.

Glad you saw improvement when you changed the plugs. I'm going to guess that they were gapped incorrectly by a previous owner or they were simply worn out plugs.

Synthetic fluids will help, top tier gasoline will help, make sure none of the brakes are stuck while driving, etc.

It's only a 4 year old car. I wouldn't expect any major problems to be prevalent, a basic tune-up sounds perfect at almost 80k miles.