i usually hear the same thing. for some reason or another the mercs get better mpg.... i dont know why.

 

Yeah' weird...

 

Maybe it's the plastic bumpers?

 

98 Merc
5.0L EFI

I purchaced this truck 3 years ago and shes my baby. When I first got her she made 16-18 High Way. I had a flowmaster muffler installed, K&N, Accel coil packs, bosch plat +4's and Bosch premium wires. I have continuously gotten 23-25mpg since. The trick is you have to keep it between 60-65mph over 65 and she starts to guzzle. Remember this beast weighs damn near 6000 pounds, thats 3 tons and these engines only put out 215hp at the crank. I figure on a good day mine is pushing 250 hp, but Ill never know unless I can get my hands on a g-tech pro or someone wants to donate some 4 wheel dyno time.

Also anyone know where you can get some headers for this beast? I am planing another flowmaster and straight pipes back, get rid of the six cats ford slaped on this thing.

 

well if i go 60-65 on the long trips then yea i'll get 20+ mpg but who the heck goes that slow hehehe. the speed limit here when i go up north is 75 mph which means 80+

 

Yeah the speed limit in Michigan is 70 but when I lived in detroit it was what ever the hell you felt like. But at the price of gas and 3 kids that like to eat. I try to keep here 60-65. $60 fill ups get old quick.

 

yea tell me about it. gas is down to $2.07 here now so i can be a little more happy with my right foot....

 

Hey FMJ,

http://www.torquemonsterheaders.com/

 

OK. Lets try without breaking my pocket book.

 

There's Ford Motorsport headers, but they are just slightly oversized versions of the originals. And they still aren't cheap.

 

My 99 mountinner droped in milage BAD,It turned out to be a brake caliper draging a little bit,each caliper has two pistons.something to check out.

We are back to 19 now
russ

 

OK, I tried my first exhaust mod today. I took out the muffler and replaced it with this:





The muffler flange starts at 2 1/2 inches and steps down to 2 at the muffler then goes up to 2 1/4 out the back. I opted to stay with 2 1/2 and rejoin the tailpipe just before the resonator. I wasn't happy about having to drop the pipe a size, but it will do until I can get around to building a 2 1/2 inch tail pipe. It's a little louder than it used to be, but not too bad.

I changed oil today and filled the tank, we'll see if my mileage changes any. MPG at today's fillup was 13.04, can't get much worse.

 

Per your request I lowered the air pressure to 30#. When I checked them beforehand they had 37# of air, not the 40# as I stated. The first tank checked with 30# of air was just about all interstate or secondary roads without a lot of stopping and starting. This tank yielded 16.1 mpg which was better than I thought it would be with the lower pressure but was not the short trips, 10 miles each way to work, that I had reported mileage of 16.7, 17.6, and 16.4 on. The second tank which was comparative to work and back trips I got 15.5 mpg. All starting and stopping was done as closely to the original checks as possible.
I don't consider 1 to 2 mpg difference pretty minimal, you may. This equates to almost a 10% increase in mileage which I will gladly take with a vehicle getting this kind of mileage and gas prices where they are. I will take them all the way to 40 now. The tires have 40,000 miles on them, at 30 to 32# inflation and are more worn on the outside than in the middle so the wear pattern is of no concern.
If you are interested in better mileage as the original poster asked about you might try to experiment a little and up your inflation to see if yours improves. I would like to hear the results.

 

Next time I head home I'll fill my tires up to 40# and drive half of the trip (about 100 miles) and then fill up. Then I'll deflate the tires to 35# and finish the trip and fill up. This is all interstate driving (70mph) so it should give a pretty good indicator.

 

I have a '98 XLT AWD with 5.0L. I've ranged between 18 & 22 MPG on the highway depending on weather conditions and speed. Locally, I am at 15 MPG or so. I am not complaining about that, it is quite good.

The SUV is all stock, has 93k on the clock, tuned up about 10k-15k back (new plugs, wires, etc. - what a PIA), with 35PSI on stock size tires.

Start with the basics, change plugs & wires, check tire pressure, balancing, and alignment, and work from there.