I have 38k on the roadster (stick) and it consistently achieved 28-29mpg while communicating between Detroit and Holland (180 mile each way) at 70-77 mph for two years. When I started trips to Midland on back roads at lower speeds, it racked up dang close to 30 mpg. There have been a couple tankfuls of gentle, highway driving where I have calculated 30-32mpg (cannot remember exactly without consulting my travel log, but I know I was pleased/surprised at the excellent gas mileage). I generally don't do a lot of local driving, but when I do it tends to register in the low 20s.

The SRT6 on the other hand never gets better than 23-24 mpg on the highway and is closer to 18 mpg in town. I think most of that has to do with the harder acceleration -- it's impossible not to push down and cause that delightful exhaust moan and rush of speed.

By comparison, my 2003 Audi 2.7T MT6 with 204k miles (chipped) has always turned in 23-24 mpg highway and 16-18 around town. But you are talking a car that weighs close to two tons with full time AWD. If I get stuck on a highway where I am forced to drive 50-60 mph, the gas mileage does improve to ~25 mpg. But it's no fun going that slow and I take a lot of 600-1000 mile trips where I'd rather burn a little more gas and get where I am going sooner.

 

It's all in how you drive. Aggressively or non-aggressively, how soon you get into overdrive, how much you coast (manual shift cars of course), the type of terrain that you're traveling.
I have never owned a car that I wasn't able to get better gas mileage than the EPA said I should be able to get. Probably because their figures are averages.
When most people say they have achived 30+mpg with their XF, they're relating some of their best tankfuls. Not an overall average.
I've been keeping gas records on every vehicle I've owned since the oil embargo of 1973. It didn't matter if it was on a fuel sipping Honda CRX HF (best ever at over 50 mpg) or on my 69 Dodge Hemi at an average of 13 mpg. I just thought it was interesting to see what they actually got.
As they say, "Your mileage may vary".

 

You miles may very: exactly! When I first got the car I never babied it. I was always heavy footed and averaged around 25-26 miles per gallon. After a few years on the car and on myself I now really baby my vehicles and get much better gas mileage averages out of this car in particular (constantly 30 miles per gallon average.) It is just all where and how you drive.

 

Just got my 05 manual a week ago and I am getting horrible fuel economy! I refilled and tried to shift early at 2K to see if will improve, but still nothing? First half tank netted me just over 100 miles. At 80mph on highway, this car runs at 3k rpms in sixth gear? No way to get mpg's like that. I am looking to get average city/hiway mpg of low teens. Thats no better than my Ram Rumble Bee that I traded in to get a fun car with better economy. I like the xf but almost wish I had my Bee back, power and looks too! Checking the plugs this weekend and air filters too. Something has to be wrong.

 

Something has to be wrong with your car......my 07 6 speed averages >25 mpg....I'm the original owner and it has almost 80,000 miles on the clock. That's 75% highway...70-85 mph .

 

i was averaging ~23mpg. i purchased the ultra-gauge and 2 of my gauges are instant mpg and avg mpg. if anybody has this you know what i mean - you really do change your driving habits. red lights, trips to the atm, etc. all effect you avg mpg. i sit at a stop and watch the avg mpg click down - seemingly very quickly. i'm a little lighter on the foot now and i've gotting my avg up to 25 but the car is too fun to be light all the time. stepping on it from a stop and you get ~3mpg on the instant gauge. i have calibrated my ultra-gauge for distance and fuel as per the instructions and my trip odo, mpg, and fuel level is dead on.

 

Now with the little mods I have done Im seeing a consistent 21-24 in town and 29-32 on highway. Depending of course on my foot. When I first got my muffler I got 20 in town for that tank lol...

 

Interesting...My 05 has 22k on it now and my mileage averages 27 - 29 mpg. This is a combination of town and interstate. The Toyota I sold averaged 32 - 34 mpg...but everyone has a Toyota.

 

Wonder why the wide disparity? It can't just be driving habits...

 

Nope, I think that I am having some issues with mine. I did drive a red 06 for the day before buying my black 05. the red 06 didnt handle as well (felt looser), had more miles, more wear, and more expensive, but did have, noticeably, more power and better fuel economy. I just assumed it had k and n filters or something and I only drove this one for 10 minutes so didnt get to test out fuel economy. I just want it to run like it should and get mileage like it should. I didnt buy it just for economy or I would have bought a Prius, but it shouldnt be at V8 truck economy either, lol. Hopefully will get to the bottom of it this weekend??? Any suggestions much appreciated/// Chuck

 

It will be interesting to find out...I don't have a clue even where to begin, except that I can't confirm the condition of the spark plugs in the car...maybe that's a starting point?

 

Plugs are the first orders of business.

 

There really isn't much else...if the coil packs fail, you know it...

 

I see that some people here get better miles than the sticker said on it when it was sold.

Normally people never reach those mpg figures and complain that the fuel economy is not what was written on the window sticker.

The 2004 NA 6 speed in Canada said 20 mpg city and 33 mpg highway. This would equate to 16.5 and 27.5 m/g (US) in the US. I think that these figures are probably not to far off the mark, especially the highway figures. I have no experience with the city travel figures. Anyone getting over 30 mpg in the US must use a feather cushion under their right foot.

The discrepancies could be caused by the heavy feet of some and the poor bookkeeping of others.

A stronger accelerator pedal spring saves gas. Maybe that's the answer.

 

I can say that I don't have any math errors...have an iPhone app that calculates all of that for me. Since we've had the car, we're averaging 22.1 MPG, with a high of 25.4, and a low of 20.1...

 

My roadster window sticker says 17/25. I drive it rather lightly, in that I generally shift around 2500-3000. I rarely do all city driving and my mixed is in the low 20s. I calculate (manually) 27-29 mpg on the highway at 70-80, and that has been consistent since I bought the car. 200 miles per tank is terrible and something is wrong -- I see close to 400 on the highway. Certainly check tires, then pull codes, check air filter. You did not mention mileage but it's possible 12 new plugs will help. Make sure you're running 0W-40 full syn and not 10W-30, although that should not make that large a difference.

 

I have noticed via my UltraGauge that the MPG is better closer to 70...

 

Sticker on my 07 6spd says 17/25.......sticker on my 08 automatic says 19/25.......glad I don't live anywhere near the kinda city they base their test procedures on.....

No question that if you took a long trip & could control yourself & keep them at 70 mph they will get 26 to 28 mpg. I got about 26 on a trip where I took it over 130 mph.

Pure premium seems to make about a 1 mpg difference over the 10% ETOH blends.

I think with pure premium that if you took a trip & kept it at 60 to 65 mph....someone might ave 30.

 

Mileage has to do with many factors. Driving style has a lot to do with it...given the mechanics are in good condition, tires are properly inflated, etc. The more highway miles the better the mileage as the stop and go kills the average. That's just my 2 cents worth. I check my mileage at every fill up...and do the math. My old Toyota had a computer that gave you an average MPG...but it was never close when the math was done. I had kids argue that the computer was more reliable...math must have not been their subject in school. Do the math...

 

Just filled up the 6 spd. 278 miles on the trip meter since last fill.....stuffed another 6/10 of a gallon in after it stopped by itself......total = 10.7 gallons......= 26 mpg. Did not baby the car & used air conditioner most of the week. BP 92....I think it's pure gas / no ETOH. $3.66.9/gal (Kansas).