My 2010 XF Premium has been getting 13 (city) / 18 (hwy) since I brought it home. My fuel mileage calculator also subtracts nearly 2 miles for every 1 mile I drive. The vehicle's mileage is 75% hwy and it is fueled with premium. I understand it is not a fuel efficient vehicle but is all this normal?

 

I have a XF Premium, 2010 model year, and get about 23.5 mpg on average with a mix of town and toll road driving. I have kept a running average since I got the car and my average is based on 26K miles over 2 years. On a day to day basis I get about 24 to 25 mpg when traveling to and from the office. However mpg depends heavily on how you drive. I keep to the speed limits which vary from 30 mph on local roads to 55 on urban roads to 70 mph on the toll road (the toll road accounts for half my journey) and i notice that mpg is about 19.5 mpg for the first half and after the toll road section it can go as high as 25 mpg.

I would suggest that your mpg seems low but bear in mind that short journeys, cold temperatures and a heavy right foot can all affect your mpg negatively. I live in Texas where the car warms quickly and I travel a reasonable distance each time I travel (in Texas all distances seem to be some multiple of 15 miles!!) with a fairly gentle right foot.

Hope this helps.

 

Although computer generated numbers like mpg, fuel range etc. are nice to look at, the only real way to get a true number is to fill your tank... write down the mileage and do the same the next time etc. Calculate the actual miles driven to the actual gallons of gas used and see the difference between the two... I'd be surprised if they match up (if so, Jaguar has something over other mfg.’s). I found with my previous car (CTS-V) that my best fuel mileage came at 3k RPM's at 78 MPH... not realistic but my on-board computer thought so...
Give it a try... you may be surprised... hopefully to the good

 

Our weather has been relatively hot and humid. We travel about 30 minutes city (30mph) and 1.5 hours (75mph) per day (5x weekly). We're easy drivers and don't tend to get on the gas hard. The fuel average has risen by .2 each week for the last 2 weeks but were still several numbers below the estimated 16/23.

 

I'm quite happy with my 2010 premium. Total average for the first 17000 miles is 18.6 MPG for my type of driving and mix of roads. Best I ever got was 27.8 MPG on 105 mile mostly highway trip, keeping the cruise speed between 70-75 MPH.
This average is actually better than my last car - 2007 Infiniti G35X which is smaller, lighter and V-6. That car averaged 18.1 MPG for identical driving.

 

I'm very happy with mine regardless but just wanted to feel out others advise in the event it was an issue needing attention.

 

The average fuel consumption display is inaccurate, at least as compared to service station displayed delivery volumes which is another whole can of worms.

Are you driving in D or Sport? Only in D will you get good fuel economy.

This car has a very low drag coefficient and also low total drag so fuel economy is much better at constant speed than in City driving. You should get about 50% better fuel economy at 70 mph on the highway than in City traffic. 13 mg in the City seems a bit lower than you should be getting but that depends on traffic and average speeds. Highway fuel economy should approach 26 mpg. However, before you go running to the dealer check a few tanks manually by dividing the trip odometer by the fuel put into the tank for several trips and average the number.

Bear in mind that fuel is sold by temperature corrected volume, not mass, but is actually consumed in the engine by mass so measured fuel economy in mpg calculated from service station pump volumes displayed on the pump varies with ambient temperature as compared to the reference temperature for the fuel sold to you. In Canada that reference temperature is 15C. If the fuel in the underground delivery tank is colder than that you get less actual volume than indicated on the pump. If the fuel in the underground tank is warmer then you get more volume than indicated on the pump. I do not know what reference temperature is used in the USA.

I think the onboard computer uses the numbers from the ECU to calculate fuel consumption which may mean it uses the mass of fuel deduced from the mass of the air taken in (emission controlled engines burn very precise amounts of fuel exactly proportional to the mass of the air drawn in.). This will cause an apparent error when you compare the display to your manual calculation which is based on displayed delivered volume on the service station pump, a number that means very little from a chemical point of view. Basically, absolute fuel economy cannot be accurately measured for the lay person. Fortunately, the only number that actually means anything is dollars per mile for fuel consumed and that depends on the price paid...... precision eludes us.

 

I would have to echo the same comments as above about fuel mileage. With my '09 XF Premium I get an average 23mpg getting 25.5 to 26.5mpg on the highway with the cruise control set at 75mph with the AC on.

 

I drive in "D" and have not experienced much city traffic as of yet. I will try manually calculating instead of relying on the computer's numbers. That's for the great info!

 

Interesting point about temperature corrected fuel deliveries in Jagular's posting. The US does not use temperature compensation for fuel deliveries at the pump, Canada does. Hence when it is hot (in the US, anyway), you will get less mass, since the fuel meters are based on volume and not mass or specific gravity which is the only way to get a real measure of fuel efficiency.

The rule is that you should wait until it is cold to get your fuel, but the tank temperatures do not change that much over the day (they are very large and below ground so they do not change much on a day by day basis) so it make little difference, unless you fill up just after a delivery when the fuel is delivered hot (in the summer in the South of the US, anyway) when you will get a raw deal. Countries with large swings in temperature during the day (which includes the north of the USA) should use temperature compensation but this is a seasonal variation not one that is detectably week to week in any one season.

However given the change in volume for every degree change in temperature (0.068% per deg F change in temperature), it is unlikely that this is responsible for the variations to the norm you see.

My data was taken from the pump readings (+/- 0.3% at what ever temperature you are measuring given that it is volume and not specific gravity and thus not necessarily representative of the calorific value of the fuel) and not based on the car based fuel consumption data. However I did compare it to the car data and found that the car data did not deviate that much (+/- 3%) which I consider reasonable).

So given all this data I would still indicate that your fuel consumption was a little high but maybe you have a heavier foot than I have :-)

 

I would sit tight for a while and not fret too much just yet. Reports and experiences filtering in seem to indicate the 5.0L engines by and large use a little oil and have higher fuel consumption than expected early on. The good news is owners report the oil use stops after the first service interval, and mileage keeps getting better as the miles rack up. Most report about what the sticker says after 20K or so.

I've asked, but as yet haven't gotten any explanation........

 

2011 XF Premium, 18k miles, 18.5-20 mpg suburban driving, 26.5-28.8 mpg highway @ 75-80 mph, using BP Ultimate. Couldn't be happier!

 

Its astounding that your mileage is that poor. I have experienced generally 19 MPG and on highway trips about 27 MPG @ 70 MPH with my 2010 XF Premium. I have no answers. See your dealer.

 

I have a 2009 XF premium and I get about 18mpg. My typical daily commute is about 18miles to work one way (mostly hwy miles). I also live in texas where it gets to about 109 degrees so I have my AC on most of the day.
A few months ago, right after i filled up my tank, i reset my trip dometer to zero and used that as a gauge to see what my average was up until when i had my next fill up.

Hope that helps..

 

I have noticed that Ford and Mazda engines are quite "tight" from the factory (so was the engine on my Alfa Romeo). The performance and the fuel economy both seem to markedly improve around the 40,000 km mark (24,000 miles). My '09 is approaching 40,000 km and the pick up and go seem noticeably better over the last few months of driving. Haven't really kept track of the fuel economy. However, for such a big car with a powerful engine fuel economy on the highway seems magically good, approaching 30 mpg (even per the smaller US US gallon) on occasion.

 

A quick update on my gas mileage...... took the XF to Lake Placid, NY this fall. Four of us in the car, full trunk, all back roads through, MA, NH and VT to NY, averaged 27.1 mpg. That said, got home took her in for a winter checkup at my local Jag dealer. They found only one of my fuel pumps to be working so they replaced both. My mileage is now averaging 22 mpg highway and backraods. So maybe it's time to disable one of the two fuel pumps?? A little less HP for better MPG??? :-)

 

High alcohol fuels will deliver poor fuel economy. Also, these engines benefit from at least 10,000 miles before you wiil see the fuel economy they are capable of. My 4.2 gets 15 to 27 mpg US gallons. The 5.0 is supposed to be as economical as the smaller older engine.