I just did a preliminary gas milage calculation on my '99 F-150, and I came up with about 10.5MPG! Is there something wrong here? I know my truck is no fuel miser, but I at least expected 13-14MPG. I do mostly city drving, with my daily average being about 13 miles, with a few longer side trips every once in a while. I'll do a more precise calculation next time I fill-up.

My truck is an extended cab with the 5.4L, 2WD, 3.55 rear-end, and about 67,500 miles. I'm wondering if there's something mechanically wrong with the truck to cause such bad gas milage. I changed my fuel filter about 12K ago, and my air filter looks fine right now. Love to hear any thoughts on this.

 

Bryan,

First thing: are you calculating the milage based on fuel used or tank size? Second: Have you checked the accuracy of your odo? The odo on my 97, F150, 2wd is very accurate with the stock tires (0.1% error) but was about 7-9 percent off (low) with slightly larger tires on it. I checked the accuracy of the odo/speedo with my GPS.

If the truck is running well, I'd start by making sure you're basing your milage on fuel used. I only say this because I've seen so many people base it on tank size. Then check the odo/speedo.

You may also want to check out some other threads here. I've seen alot of milage reports but can't recall what others are getting with your specific model.

One other note: I notice about a 2mpg (or 50 miles/tank) difference on the highway between traveling at 70mph or 80mph.

 

My truck is an `02 KR SuperCab with the same drivetrain as yours. 49K miles on it. If I drive conservatively around town, I get 14-15 MPG, Highway driving, 18-19 MPG. If I get into the throttle a lot around town, I get 11 MPG. My .02 worth.

 

Heh...I dont even worry about it any more. Oversized tires, and I can never remember to reset the odo when I fill up.

On second thought, today is the first day within the past 3 months that the tank has actually been full.

 

Grsyhands: Yeah, I'm pretty sure I calculated it right. But I'll make sure to do it the right way next time I fill up. I'm still running stock-sized tires, so my odometer should be fairly accurate. Can you show me how you calculate your gas milage so I can make sure I'm doing it right?

KingRanchMan02: Somewhere in the region of 14mpg is what I was expecting. I drive it pretty conservatively, no jackrabbit starts, etc.

 

To calculate it, make sure you fill up on a level surface, then make sure you top it off the same amount during each fill up. After you fill the truck and top it off, reset the odo and drive as normal. You can fill it back up at any time just make sure you top it off to the exact same point (I top mine until I can see it in the neck). Then just do the math MPG= Miles Driven/Gallons to refill.
I have the 4.6L super cab and get approximately 19.5-20mpg.

 

change ur 02 sensor my mpg went up 1 mpg when i did this at 65000mi

 

Before I started spending money changing sensors, look at and clean the MAF. A dirty MAF can kill the mpg on a truck. The worst case I have personally seen was on a 2002 Explorer with a 4.0L. The Explorer was getting 9mpg. We found a ladybug carcass on the MAF. Once we removed the dried up bug, thoroughly cleaned the maf and reset the ecu, the Explorer ran better and got 18mpg again.

 

my 97 was getting about 11mpg around town(perhaps part of the problem is my heavy right foot) but with a K&N fipk kit (the intake kit not judt the drop in filter) and a throttle body spacer and Gibson super truck exhaust its up to around 13.4(still with the same heavy foot).

 

jbabbler: I'll take a look at the MAF. I'm sure it's never been changed, I got the truck with 53,000 miles on it. How should I go about cleaning it? Might look at the O2 sensor, too. Heck, I bet it's about time for all those dang little sensors to start crappin'-out!!

 

Bryan,

If you haven't already done so, look around this site. I'm sure I've seen a number of posts regarding cleaning the MAF. Swaping out O2 sensors would run you between $200-$300 for all four. I wouldn't bother unless you're getting a code.

 

OK, now I'm wondering if a complete tune-up on this truck is in order. I have no idea what the previous owner did in the way of maintaining this truck. I got it with 53,000 miles. I might look in to doing that. Better safe than sorry!

 

Dont worry about plugs at 53k. Just do all of the things I listed above and it will run sweet

 

Clean the MAF, replace airfilter with well known brand, change oil/filter and use the recommended 5w-20 oil, ford synthetic or mobile 1. Have tires balanced, and last but not least take it to the dealer, and have them drop the tranmission pan, replace the filter and all the fluid. Do not take it to a quick lube or tranny shop as they will most likely do a flush on a machine contaminated with the wrong fluid. (Big repairs if the wrong fluid is used) Ask if the plastic plug was still in the pan, an indication the pan was never pulled. If you are having idle, stumbling problem sometimes after you do a cold start, replace the IAC.

 

Do you like to let your rig warmup for 15 minutes or so in the morning while you drink your coffee and read the comics? And again,in the evening, do you start it 15 minutes before you punch the clock? If so, that can be a big gas waster right there. It prolongs the time in open loop because it doesn't warm up very quick with no load on it. It also burns gas while the truck sits, contributing nothing to vehicle mileage, thereby reducing the average. The best thing to to if you are a warm up guy is let it idle for about 1 minute to stabilize the bore and combustion chamber temperatures, then drive gently untill you are at operating temperature. Also, top off your tank the same way, consistantly when you fill up. Don't just top off the tank to the first click once and then stuff $5 extra in the next time, then 1 extra gallon the next time, or your results will be very misleading. Consistency in your calculating proceedure is key. Also, Oxygenated gas costs me about 1.5 MPG in the winter.