Old guy new to Eco 2001 Mustang Sport Coupe V6
 

I bought the car new and for a few years it would get 31 MPG Hi Way. Since then it has deteriorated to 22, I've wondered if it was because the engine wasn't designed for the current alcohol levels in the gas. At 50 K miles I installed new double platinum plugs and it appeared to get slightly worse mileage. It's hard to drive on the highway at less than 70 but I tried it today, so it is do-able. Looking for tips on checking programing, it passes smog perfectly, but maybe the tune can be changed? Has anyone tried advancing the cam timing? Much cheaper than hi compression pistons. Pat

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. :thumbup: :)

2001 V6 Sport Coupe
 

In my introduction I mentioned being older (77) so I don't have to do the 8-5 commute. But I do have to travel on the Hi Way for medical checkups as well as to visit son & grandson, each trip is 260+ round trip. Since buying the car traffic in town as well as the Hi Way has increased so that it is harder to drive at a slower speed not counting traffic jams. This last tank with one 270 mi trip worked out to 26.05 trying to drive at 65 which is an improvement over trying to drive 72 with the pack. When I bought the car I was told it was a Sport Coupe different from a regular V6 in that it was made from a leftover 2000 GT chassis with 4 wheel disc brakes and 16" aluminum wheels and it has dual port cylinder heads. I have no information on the power rating but at 4000 when the short port butterflies open up it makes respectable power. The engine has 92,178 trouble free miles on it, I use mobil 1 synthetic 5w-20 and change it about once a year which is about 6,500 miles, the trans is an AOD also trouble free. The 1st set of tires were good for 65,000 and it still has original rotors & pads. Other than Hi Way about a third of driving is for shopping and waiting at traffic lights, some times we take a slower longer route without any lights. It also came with an air-dam, skirts and a horizontal spoiler mounted on the deck lid, while they were mostly for looks they might also help. 7 years ago I was stopped at a hi way jam and got rear ended by a full size Riviera traveling 70 MPH, the impact punched the front of the Riviera back to the windshield and the Mustang was able to drive away to a safe spot. Visually no damage was obvious, the seat recliner mechanism broke and I had serious back and neck pain for 2 months. The car and I both got therapy and no damage is visible. The rear bumper impact absorption systems did their job as they and the plastic fuel tank had to be replaced. Stay tuned, I'll describe my '85 GT hatchback 5 sp. that gets 28 hi way at 70 + with the original Holley. Thanks for your in-put and inspiration, Pat