Hello everyone,

I am not new to the forum but it has been quite some time since I visited. I am experiencing a sudden drop in gas mileage with my 2003 F-150, 5.4L, 65,000 miles. Basically I am a guy who reset my trip odometer every time I fill up. I was getting on average 350 miles per tank full. I am now down to around 300 or less miles. The sudden drop came soon after replacing all four tires with Goodyear Fortera tires. Not believing that new tires could affect my gas mileage that much, I took the truck to the dealer. They stated that the computer reported that cylinders 3 & 5 were dropping out. They suggested new plugs and an injector cleaning. I begrudgingly agreed to the service and it did nothing. Other facts: I have kept up on oil changes, and fuel and air filter changes. I did have the dealer complete 35,000 mile Ford suggested maintenance checklist. I have not completed the 65,000 checklist yet. Does anyone believe it could be the tires? Any suggestions would be appreciated.

Trab

 

What did the dealer charge you for the spark plug change if you dont mind me asking?

 

Cold weather and possible gas reformulation for winter, depending where you live.

 

Are the tires you put on the same size as the last set?

If they are, then I would also say its probably just due to the cold weather and different gas.
Hold out until the warmer weather gets back, and see if your mileage returns to normal.

 

Thanks for replying all. I am just getting back to this from my Christmas get away. I am in Indianapolis IN. They may have started a winter mix around here but I am not sure. Do any of you think that stepping up to 89 or 91 octane would help? I could try a tank full or two and see what that does.

jvangel - I was charged $289 for the plug change, Ouch! The plugs were only $6.89 a piece. Of course they explained to me how hard it is to get to them.

Another question - At 65,000 plus miles am I ready for front end bearings?

Thanks again,
Trab

 

I have the same problem. I live in Maryland and they change the mix in the winter as well. The cold air also gives you more horsepower which will decrease you MPG. In the summer my MPG goes back up!

 

Ford suggest only running 87 in the modular motor unless you have a programmer installed.

 

yeah, stick with the 87, your engine isn't designed for the higher octane gas.
BTW, I wish i could still get 300 miles to the tank, right now I'm around 250 miles per tank, so don't feel too bad.
I think my injectors need to be cleaned or replaced b/c i have been having way too many problems with my truck lately (probably also including the bad gas mileage) anyways, if you don't mind me asking, how much did they charge just to clean the injectors? I didn't know they could do that, thought you just had to replace them.

 

It's just the winter blend gas and cold weather. I usually see a 15-20% drop in my gas mileage every winter. Not something I like, but something you just have to deal with. I would advise against using any octane higher then 87. Just stick with a quality gas.

 

I normally lose 3-4 MPG in the winter. From warming the truck up every morning for 10 minutes (defrost windows) to low air pressure in the tires on the morning commute, it takes quite a toll in the winter.

I typically gain/lose 2 MPG when replacing tires. I get better MPG with the conservative tread/long life tires than with a good set of all weather tires with deep cleats.

 

could be both gas and tires, I put new goodyear ats' on my truck and lost 2 mpg, later put on michelines and got it back (like in the previous post I went to a harder hwy tread) also this past weekend I took a road trip, the gas from WA got 15mpg and the gas from MT got 17...and I was driving faster and in a rain storm on my way home, go figure.

 

I think its the cold weather too. I went from 16mpg in my 99 Expy to about 13.5 to 14mpg. I have the 5.4. I notice the engine seems louder when accelerating since the cold weather hit, of course I'm running a K&N filter on it too.

 

Winter kills mileage.

So far, I've logged 15.3 twice, 16.98 once, 13.5 once, and then a 90% highway and interstate run of 19.82 mpg. I was stunned w' the 19.82.

I have the 5.4 supercap 4'x 4'. It is a 2003 w' 13,000 miles, I just bought used. It has 3.55 gears

My tips are using overdrive only doing over 50mph, using a bed cover, and driving very easy. That being said, these things suck gas in town, like my 13.5 reading got, but do great on the highway, at almost 20 mpg.

 

Porky - $99 is what I was charged at the dealer for the injector cleaning.

All - I'll go with the gas mix and colder weather. I haven't finished out the most recent tank full but it has been up in the 50's around here in temperature. It appears that I am going to get better gas mileage this tankfull. I'll let you know.

 

I just Fortera's on my 2001. They definitely affect mileage for the worse but also help with stopping distance. They have higher rolling resistance compared to most all seasons. Consumer Reports noticed this as well in their rolling resistance tests. It still won for best overall SUV/truck tire.

I'll live with the worse gas mileage as long as I get better tread life than the crappy BFG Long Trail TA's.