I have a 2006 F-150 Lariat with the 5.4L Triton. I used to get 15 mpg when I first got the truck. Then it dropped to 14.5 mpg and it stayed like that for a long time. Within the last couple of months, since about late-summer to early fall, my mgps have dropped from the 14.5 all the way down to 12.9! I used to get 550-600 miles a tank but now I'm lucky if I break 450. Something has to be wrong but I don't know where to begin. My truck just hit 40K miles which from I've been told since forever that 40K is a motor's break in point and that the motor typically performs better once it hits that mark. Well I must be in trouble because the truck is under-driven for being 4 years old and I've already lost valuable mpgs.

I use good fuel, change my oil ever 3,000 miles and I use good oil too. I recently put some fuel injector cleaner to see if that would help. I do add it every oil change too but I added some extra recently just to see if it would make a difference. I have a K&N air filter which I recently cleaned so that shouldn't be it.

The only thing that I have done recently is buy new tires which are slightly taller. My truck came with 265/60 R18 but I went with 265/70 R18 to have a little taller tire to fill out my wheel wells as I thought the factory tires were too small. Even then when I changed the tires my mpg was 14. It stayed there a while then dropped to 13.4 and now all the way to 12.9.

I can't keep losing mpg. If any one has a suggestion please let me know. At the rate I'm going by 2012 I'll be getting 10 mpg. Help please. I;m all ears.

Thank you for your time and have a nice day.

 

Winter gas.

I went from about 15.5-16 on the highway, to 15 with the 35" tall tires

ALLLL the way down to 12.5-13.5 with a 20 mph headwind. Then, without mcuh wind, I was able to scramble up about 14.5

I have a Tundra.

Same effects with your truck though and in a few months you SHOULD be back up. If not, I'd be looking at spark plugs, air filter, etc.

-rockstate

 

Really? I didn't think there was a difference with gas in different seasons. I live in New Orleans so we don't have much wind here at all. Our cold fronts bring some wind but for the most part we have mild winters. Not a lot of wind. Are fuel filters easy to change or is that something a experienced mechanic should tackle?

 

Yeah google Winter Blend gas and I'm sure youll get a lot of hits.

Never changed a fuel filter on an F150 before so I dunno... why would you need to change it? You're not experiencing any of the issues exhibited by one going out or clogged or anything.

-rockstate

 

Oh I just realized you said air filter. I thought you said fuel filter. Well I have a K&N but I guess I could buy a new one because I've never been sold on that million miles thing.

 

Honestly, you're probably fine on air filter too.

My truck has 55K miles on it and it was fine last time I checked it at around 45k miles.

same with spark plugs - they're good for 100k miles.

Wait til a few more people look at this thread over the next few days, and it'll put your mind to ease on the winter blend. IMO that's it... there's a thread over there on the tundra forum too.

Winter gas sucks! - Toyota Tundra Forums : Tundra Solutions Forum

-rockstate

 

Winter blend fuel is a SOB. My MPGs have gone from mid 14s per tank, to low 12s per tank. Same route daily. Same miles. Same driving habits.
My father does some chemical and process work around the fuels refineries here in VA. He claims that winter blend has more Oxygen and the gelling point is different. I couldn't keep my attention long enough to understand how that has effect on my mileage.

Anyhow, as for that K&N filter. How long has it been on the truck? You might want to pull out your MAF sensor and see how coated it is. I had a K&N for a month, and it caked the MAF with oil. I'm now back on paper Motorcraft filters.

I hate winter. Supposed to snow here today, and even though it's just 3-5", the whole city shuts down. Annoying. Not to mention that I'll be on pins and needles driving to and from work because of the idiots around here that think they can speed in the snow. Fun!

 

I know in our area the percentage of ethylene in the gas is constantly going up, edpecially in the winter. It burns hotter and faster. I lost 2 mpg when the % went up to 10%. I went and purchased a sct programmer from 5 star tuning and it gave me back what I had lost; in economy mode. I still only get 13mpg. Remember also in the winter most people allow their trucks to warm up as well. All those minutes in a week add up. These trucks dont run on air.

 

Here's a little insight FWIW:
Question about Winter Blend gasoline

 

i have the opposite issue, my truck gets BETTER mileage all of a sudden. the same grade and amount of gas at chevron gives me 100km (yes im canadian) LESS per tank than esso gas. i thought it was fluke, like maybe esso put in a higher octane level gas into their regular tanks by accident but its ongoing for over two months now. i put on 80km a day so im now an esso customer.

 

MCDavis- I like how the EPA claims there's no difference and summer blends are more expensive to produce, yet the gas stations charge more for the winter blends! I only lose about 1 mpg during the winter, so I don't complain too much..

 

Yeah I noticed this too. Everything I read says that summer blends are more expensive to produce, yadda yadda. But yet the cost of a gallon just went up some $.15-.20 here in Richmond. WTF? I guess that whole supply vs. demand thing plays a factor. I took two economics courses in college, and my logic still gets in the way on how that stuff is supposed to work and affect our lives.

I love my truck, enough in fact that my wife thinks I'm crazy, but $2.89 a gallon @ 12.1 mpg (last tank) sure does put a dent in my wallet.

 

I have similar trouble with fuel mpg. I was steady at an average of 17.5 mpg. I all of the sudden can't get above 15.5-16 mpg. I just changed oil thinking it would help. I use mobil 1 fully synth. The air filter is 6 months old and tire air pressure is good
My 2004 lariat 5.4 triton is at 140.000 milesany suggestions?

 

I'd look at the MAF sensor, the fuel filter and the air filter. Has your style of driving changed? (more stop/go in traffic?) more idle time on warmup? faster acceleration situations?
Tire size change (taller = distorted mpg) 275/65/18 load range C up to 275/70/18 range E with a much straighter sidewall =33.26 in height v/s old rubber @ 32.2 in height and a much softer sidewall will make your computer #s look quite different.
It could be combination of a few small changes compounding.

 

...so summer gas costs more to produce, is sold cheaper, and gives better mpg than winter gas. Winter gas is cheaper to make, is sold at much higher prices than summer gas, and gets worse mpg. As usual, this doesn't make sense. Kind of like our govt forcing the use of ethanol, which costs more to produce than the gasoline it replaces, and produces less energy per gallon at the same time.

I wondered why I suddenly lost a couple mpg lately myself. Now I know why. The gummint is making things better.