I have a 2005 KR with the 17,500Miles, 5.4L 3Valve, ABout 2 Months Ago my Gas Mileage on the Highway went Down Hill. I went from 17-18mpg at
69-72mph to 15-16mpg at anything over 62mph. Any Ideas what could be Making this Happen????
I have not made any Changes to this Vehicle in the Last Year.
Thanks. KR Paul

 

They, fuel companies, change the fuel blend for winter time. That is most likely causing your drop in mileage.

 

Change your air filter and make sure the tires are inflated properly. Plus what Gearhead said about the winter fuel.

 

As strange as it sounds, I've also noticed a drop in mileage every time I take my truck in for service. It seems to take 1 or 2 tanks of gas and the mileage comes back up.

I did a big trip over Christmas. 1 day was 7 hours of driving, 3 other days were 12+ hours each day. The worst mileage I got was 12.85 M.P.G. driving through the rain on December 22. The best I did was 15.7 M.P.G. on December 27, and that was the stretch going through the Blue Ridge Mountains.

 

As Gear mentioned, it's the fuel formulations that the refineries pump out.

If I recall correctly, the additives and such found in summer fuel are there to optimize fuel efficiency and thus, cause less emissions (smog & a host of other emissions). Butane, I believe, is one of the main ingredients that fluctuates in the mix.

Butane doesn't have as much compressive qualities before it expands during the 'burning' of the fuel and thus, there's a less explosive 'opposite reaction' for in the fuel chamber of your engine. That said, this creates or yields less energy and thus, less MPG.

I think that's all correct... I may have it off somewhere but, that's the gist of the situation.

It's not uncommon to loose 1 to 3 MPG when the winter fuel crossover occurs...

 

Agree with all replies.

Try this.

With your truck off, disconnect your Neg battery cable and then turn your lights to on for 2-3 min.

Turn your lights back off and reconnect your battery cable.

This resets your PCM. Think of it like clearing the RAM on your computer.

 

I'm getting between 11 and 12 mpg in the city. It should get better as the engine breaks in, at least I hope so.
Sure glad gas prices dropped

 

13.4 is the best I have been able to get out of my 07 KR.

 

14.2 mpg

Now I've only put 5K miles on it in 7 months so I'm sure the motor is still "tight". This is evident because the first 3K I was getting 12.1 mpg and now it's been improving slowly.

The miles I have put on it have been a mix of highway and street. There was even a 450 mile trip where I was in 4WD half the trip.

 

I've lost probably 5 miles per gallon since the start of winter....Will be changing my air filter soon and cleaning the MAF so hope that helps a bit but I know it is alway more of a pig in winter!! LOL

 

I have an 05 SCREW best so far is 15.7 over a 345 mile trip. The KR only has 6500 miles on it. My 05 Expedition with the same drivetrain ,20K on miles, no probs busting 17mpg over the same trip. Both vehicles have the K&N filter.
Hey go figure.

 

I have an 05 KR that is getting around 13.3 mpg on the highway and about 12.5 in the city. I hope to improve this some how, I have 3.55 gears btw.