Welcome aboard, fellow Mustang V6 Coupe owner!
Please give us some more details.
How many miles are on the car?
Have your driving conditions changed?
Has your driving style changed?
Is your transmission manual or automatic?
Is this your daily driver. If so, what is your commute like? (speed limits, distances, stoplights, stop signs, traffic, etc.)
Do you
only drive it on the highway? If so, limiting your speed to 65 MPH can give impressive results. I averaged over 34 MPG from Flagstaff, AZ to Foothill Ranch, CA last July by limiting my speed to 65 MPH. Aerodynamic mods can also help on the highway. I haven't experimented much with that, yet.
There are a LOT of hypermiling techniques
here. Adjusting the "nut behind the steering wheel" is a very effective modification.
In my experience:
An underdrive crankshaft pulley is good for about 1 MPG.
Switching from 5W-30 oil to 0W-30 synthetic oil is good for about 0.5 MPG.
Please start a fuel log so we can track your fuel economy and help you improve it.
My current daily driver (when I don't need a truck or 4-wheel-drive) is a 2007 Mustang coupe (purchased new) with a 4.0 liter V6, 5-speed "bolt-action" transmission, and 3.31 rear axle gears. It has just over 68,000 miles on it, and still has the original spark plugs.
My normal morning commute is 16.7 miles (through town) with 3 stop signs and 20 stoplights. My normal afternoon commute is 20.3 miles (15 freeway miles) with 6 stop signs and a railroad crossing. So my driving is roughly 50-50 city-highway. I
rarely use AC - I live in
northern Arizona at >6000' elevation.
It
is possible to average over 30 MPG with a Mustang V6.
