Why do my MPGs stink so bad?

02 winnie sport with the 3.8 and 140k.

i can drive on flat land on cruise at 65 and still will only pull 18.something.

when I got it at 110 it would pull 24 mpg in a similar situation.

City is like 15.

I dont know why its so poor. otherwise car runs great.

the following is new since ive owened.

plugs wires coil
174 fix
IAC
Map senser cleaned
pcv

tons other stuff.

no codes.

Erik -

Since no one else has chimed in...

My van gets about 17 around town (random kid shuffling duty; wife's work, etc.). I believe I get close to 20 on trips when it isn't heavily loaded or towing. But it's a pretty rare occurrence when we're on the highway that we aren't towing a trailer or using a roof-top carrier, both of which hit mileage - so I can't really say what the max highway mileage could be.

Frankly, I'm surprised you've seen 24 mpg in the past - I've never had mileage that good from our Windstar. I've been under the impression that the Ford 3.8 simply isn't a terribly efficient engine design (in contrast, I've heard that GM's vintage 3.8 pushrod can get surprisingly good mileage), and little can be done to improve it significantly.

That said, I don't know why you're no longer seeing the 24 mpg you've seen in the past.

Some items to consider:

Are the bushings on your intake runner control in good shape? If the butterflies aren't opening and closing properly, that could play a role...

Are the brakes in good shape? Dragging brake hardware will affect mileage - and brake life.

You could try some quality fuel injector cleaner to see if it makes a difference.

My van is scheduled to take a long non-towing trip tomorrow - though I'll likely end up with gear in a roof-top carrier. I'll try to make good use of cruise control and see how well it does.

Tire pressure (I ran 40psi, well within the max rated for my tires)
Some tires have lower rolling resistance than others (I have not used the newer tires that advertise low rolling resistance but the varience is present between normal tire brands/models).
Correct spark plugs for your vehicle...they will be double platinum (platinum on both the center electrode and the ground tab)....fancy multiprong plugs have been noted to not do well in the windstar application.
Clean filters.
IMRC as mentioned above....max fuel economy is with both rails CLOSED.
Also, I note that fuel economy drops REAL fast as you get above 55.....and some states have bumped the speed limit up from 65mph to 70mph in the past couple of years.
Going 70 instead of 65 would cost me a couple MPG in fuel economy.
I did not get 24 out of my '96 on any regular basis.......21 or 22 if I took it easy on a trip.
I did, as the vehicle got older have intermitten sticking caliper issues......replacement of the calipers solved that problem.....that was at 183K miles and vehicle age of almost 11 years with factory original calipers.

I replaced the upstream oxygen sensors at around 150K'ish miles after repairing my lower intake manifold coolant leak......1 sensor had coolant stains on it....using Genuine Motorcraft brand oxygen sensors.
I got NO change in performance or fuel economy with new vs old oxygen sensors.

Buddy,
Try not to spend any $$ of yours on your Windstar unless you find something obvious.

I have done a lot of work on my 1998 Windstar - Just to improve the mileage and all was wasted.
One thing sure helps temporarily - Fill up a full gas tank with Shell Nitrogen gas for one time and then go back to your normal gasoline. This helps on my van somehow temporarily to improve the mileage.
It is probably the 10% Eathanol gas which is causing the van to give lower mileage and nothing is wrong with the car.
http://www.fueleconomy.gov/feg/factors.shtml

http://hho4free.com/gasoline_vs_ethanol.htm

I had seen a graph before which suggested that if the Ethanol content is 7 % the mileage can go down by 8%.
If I am the gasoline manufacturer I will always add 6% and not 10% Eathanol to boost my sales!

Also check this out I am not sure if this is the solution.
http://www.ngkplugpro.ca/content/contentfiles/pdf/ngksp-0506-3_-_automotive_ethanol_fuel_en.pdf

A good thing to do is clean your MAF (mass airflow sensor) or maybe have some injectors not working right.

I have probably done more to improve MPG in my 95 3.8L Windstar than ANYONE else has except that guy that pimped out a Black Windstar one time with a supercharger. Can't remember his name right off, but ya'll probably know who I'm talking about. lol

Anyway, everything I did (including exhaust) was wasted. Granted I spent money, I didn't spend insane amounts to try to get it better, but I spent money on MPG while I was chasing another problem hoping it would help. It didn't. In the end it all just comes back to physics: weight and engine design. You just can't pull more HP out of this (lol laughing before I say it) "PLATFORM". Now, if it was the same 3.8L in an older Mustang shell, then you probably could get a MPG increase out of it through many modifications you see people doing to be "street racers".

I have guesstimated that I'm getting 18 - 19 MPG if I'm right that I can go 460 miles on one 25 gallon tank and that is pure highway. City ranges from 15 to 17 mpg with "light load and no towing".

If I read that right (110 mph and 24mpg) umm...... DUDE... I don't feel safe driving my Winnie past 90 and that's just been for a brief kick or to pass a rig. I hope you aren't driving it 110 mph and if so I would think your MPG would be half as much as it would be at 55mph if so.

If I read that right (110 mph and 24mpg) umm...... DUDE... I don't feel safe driving my Winnie past 90 and that's just been for a brief kick or to pass a rig. I hope you aren't driving it 110 mph and if so I would think your MPG would be half as much as it would be at 55mph if so.

I believe Erik meant that he was getting 24 mpg in his van when he bought it, at which time it had 110K miles on it.

My '00 now now has about 140K miles on it - and I've never done better than 20-21 mpg highway on trips (when NOT towing a trailer). I suspect the van could do a bit better when lightly loaded - but all of our trips involve moving the whole family, so I just don't have data for that kind of driving.

I'd love to get 24 mpg on trips - and a similar uptick in mileage when driving around town, which is typically 17 mpg for our useage.

Now some real data for the trip I mentioned in an earlier post: With 4 people in the van, a reasonable amount of luggage, and a lightly-loaded rooftop carrier, our van got 20.6 mpg while driving from MD to OH. Most of the trip was on the PA turnpike, driving at the posted limit. I'm sure the air resistance of the carrier affected the mileage, but I suspect I would gain no more than 1 mpg without it.