I'm just wondering if there's a huge difference in terms of fuel consumption between XJR and naturally aspirated 4.0? Is it possible that a manual XJR would be more economical than 4.0 with an auto gearbox?

 

I dont think there is much in it
driven gently, it takes a fairly constant amount of fuel to shift a 1.8 tonne car along, and both my 3.2 NA car, and XJR, can achieve about 25 mpg (occasionally 28mpg for the 3.2)
driven enthusiastically, the XJR averages 17-18mpg, and the 3.2 about 21-22

So for a bit more fuel consumption, I think the XJR serves up a lot more performance

 

But if I'm not mistaken, 3.2 is thirstier than 4.0 - many posts on this forum claim that this is due to the 3.2 being underpowered.

That is imperial (UK) mpg?

 

Well, you may be able to drive an XJR in such a way that it nears the fuel consumption of the NA..... but it doesn't have 2 fuel pumps instead of one because it is capable of burning LESS fuel....

 

I too have a Daimler Six and an XJR306.
I'd say that on average the R will use 20% more fuel than the Six (4.0).
With the Daimler I get close to the 10 km's per litre.
With the R I'm happy if I approach the 8 km's.

 

Im going to come across as a smart Alec BUT my advice is if you have to wonder about gas mileage and fuel economy, don't buy a Jaguar.

 

Well, I've done about 15k miles since I converted my jag to LPG, and at the moment it's much cheaper to run than any of the modern 2.0 petrol cars - quite comparable to 1.6 or 1.8 diesels, actually! Except that it's much safer and better looking

 

In my XJR, I average about 20mpg on the highway and barely 15 in the city.

 

I've owned all the flavour over the years so here is my take on it.

....taking a look at the UK fuel economy figures and you will never see close to those, the drive cycle for the fuel consumption figures is (and still is!) so easy it was laughable back in the 80's and 90's.

The ECE15.04 drive cycle was used for the emissions test, and fuel economy was generated by the amount of CO2 produced, a very accurate measurement indeed.

Look to the US fuel economy figures for something a little more likely. The drive cycle was a little harder on the but was in many eyes a still a little too favorable.

But you have to have some set standards so you can measure apples with apples, so all this recent bleating in the UK press at the moment regarding unachievable fuel figures can be somewhat misleading.

Anyway enough of the history lesson. Around town in the real world the 3.2 and 4.0, well there isn't much difference although I still feel the 3.2 has it, the XJR (only owned autos) is a little worse...but we are talking cars that are never that great on fuel to start with. Curiously there were some figures derived at Jaguar that proved the auto's were better on fuel than the manuals, some ( I said some!) of which was due to the mismatch of the manuals gearing to the drive cycles used in Europe (all vehicle used the same gearshift points!) and the average Joe to wrongly use a gearbox.

On a cruise, the 3.2 is noticeably better than the 4.0, again the XJR is a little worse...but there is a cavet:-

The XJR....it would be fair to say they encourage some, lets say errrm enthusiastic driving, drive it hard if only to listen to the supercharger on song and then the fuel consumption is gruesome....'71 4 barrel AMC 360 Javelin and C3 Corvette mpg levels come to mind, having owned all at the same time...all good fun though, but at a cost. I always had a feeling that the XJR's fuel mapping runs very much on the rich side when the taps are open, my guess was to inhibit detonation (pinking) issues.

As the man said earlier two fuel pumps and all that horsepower comes at a cost.

but they say, your milage may differ...

 

"Im going to come across as a smart Alec BUT my advice is if you have to wonder about gas mileage and fuel economy, don't buy a Jaguar."

 

After almost 18 months of regular commuting (120 miles per day), primarily highway, I consistently see 18.5 average MPG according to the trip computer.

.

 

I discovered that my 4.0 Jag would consume much more after sitting in garage for a while. Yesterday I took it for a ride after 10days not using it and it showed me 19l/100km or something. And its not first time, I realised that consumption figures are better if it's used daily but why?