Lost 2 mpg. What is best options to improve
 

I have a 2000 F150 Ext Cab 4WD, 5.4L, with 91,000 miles. I have always since new averaged around 17-17.5 mpg. Since Nov I am only getting 15 mpg. I have done the easy things such as change gas stations, tried premium gas, checked air pressure in tires, changed air filter, changed oil, cleaned throttle body and injectors. I am thinking about installing a CAI (which is best K&N, Air raid, etc), E3 spark plugs and possibly a CAT back exhaust system and also buying a chip or tuner to help improve the mpg. Is there a simpler way of troubleshooting to get the mpg back or do I need to go through all of the mods mentioned above. When making recommendations please mention what type of exhaust and tuners would be best. Thanks in advance for everyone's suggestions.

What about your fuel filter?

97, 98, 99 Ford F150 rear seat lift kit

Fuel filter was replaced about 10,000 miles ago

I would install double plat sparkplugs (ignore the E3) and replace the front O2 sensors.

A CAI will not improve mileage (although it sounds really cool). A tuner is nice since it can read codes and you can tailer the program to fit your driving style. Expecting it to improve your mileage might be a stretch. The stock exhaust is actually a very good design with high flow and unless you have a plugged cat, I would leave it alone.

My guess is that if your mileage has been bad since November, that it may simply be winter gas formulations (or the addition of ethanol to most brands of gas in recent years) that is causing your decrease. Being realistic, 15 mpg is simply not bad gas mileage for a 4WD truck with a 5.4 engine, especially in a mixed driving situation. Are you on the same set of tires as you were when you were getting the better mileage you remember?

Add up the costs of the mods you're proposing, and it will take you years to recover any fuel savings *if* the mods kick you up from 15 to 17 mpg--and I doubt they will. If you drive 15k miles per year, the difference in annual fuel costs between 15 and 17 mpg is about $350, tops, with fuel cost at $3 per gallon.

The O2 sensors may need replacing, and you are getting near the 100k mile plug replacement interval, so replace the plugs as a maintenance item. I'm not a fan of K&N air filters; too may people oil up their MAF sensor...

Good luck,
George

Have you realized what you said in your first post about making changes or adding all those items that will cost you a bundle of $ all in the name of a couple mpg that you won't get back from them.
Cooler weather always results in a drop of fuel mileage from the richer mix, longer heatup times, changes in fuel quality, pushing through snow and just keeping the cab warm etc.
Headlites, heater motor etc also take power from the engine by extra alternator loading..
Transmission fluid is thicker when cold.
If you are not using 5w20 oil, but a heavier weight, it also has an effect on engine losses.
I agree that if the OX sensor are original, they might be benfical if replaced.
Higher tire pressures result in lower rolling resistance and plugs if old may also help but the rest is a waist of money.

My only other suggestion is to check/clean the MAF.

I completely agree with leaving the intake alone (or doing the Gotts mod) as well as the stock exhaust.

And do not run premium gas - it will not improve your MPG unless you get a tuner with a 91+ octane tune (or you advance your timing). In fact, the premium gas may actually destroy your cat.

I'm wondering just how you were getting 17 mpg I never saw anymore than 12 mpg and then 15 mpg after changing air filters.:-huh:confused::-huh

17 is damn good for this area Winter blend fuel is what came to my mind.

Thanks
 

Thanks for everyone's input. Yes I knew I would not get back the investment of the changes I mentioned but if it betters the enjoyment of driving it is a small price to pay. Most changes to vehicles we will not get a payback. I had not changed tires or any mechanical changes other than a regular oil change with 5W30 that I had always used. Like I said I have owned the truck since 9/1999 and have never gotten less than 17 mpg and that is with living in CO for 7 years running 85 octane fuel at 9000 ft elevation so it is just unusual for me to see it at 15 mpg. I also have always had a camper shell on the truck even though adds weight does help with wind drag around the bed. Maybe it will come back with a change in gas formulation so will keep checking to see if or when the mpg may return

If you want to modify your truck that's great, but don't use gas mileage as an excuse... Even if you were to make some mods that would increase your mileage just a little bit, I would bet that you, like most people, would actually see your mileage decrease because of all the new "fun" you'd have putting your foot into it.

Given that it's a 10 year old truck, you'll never get money back on mods if you end up selling it, so consider mods to be a "fun" expenditure and not much else.

And if you end up pushing it harder, you will put more strain on the engine/trans/brakes/suspension and may be more likely to break stuff as well.

Finally, I have a real hard time buying 17 mpg with a 5.4, 4WD, and a camper shell in the mountains, still. Maybe you found a gas station with a lucky miscalibrated pump :)

Good luck,
George

well, your truck is close to time for the 100,000 mile tune-up (plugs, wires, coolant flush, trans flush, fuel injector cleaning, etc; etc;) since it sounds to me like you have most of that covered, try to clean the injectors with an additive you pour in your tank. also, if you can get your hands on it, they sell an item that cleans injectors really well, but it involves dis-connecting your fuel pump power supply, your fuel lines from the fuel rail, and then you plug in the device, and hook it up to the bottle, and start the truck, let it run till it dies, then replace the lines, and the power supply to your pump. i like the first idea better, less work... LOL

dads 02 5.4 fx4 did and still does get 17mpg highway... but that is with virtually no hills, from spring till fall, very few stops, and a cruising speed of about 55. so it is possible, but kinda hard to do for a lot of ppl. with my 97 4.6 etra cab, i can get 17 during the summer, but durring the winter the best i can get is 16... gotta love winter blend...

the other week my scanguage said 18.1 with the cruise set a 55 on the taconic state pkwy. went down to 16.9 when i got to rt 84 and had to do 70 to avoid getting run over by the tractor trailers. 99 5.4l 4x4 ext cab wit 3.73 gears