I am considering buying a 2003 xj and was hoping to get better gas mileage. Other than proper maintenance is there anything electronically that can be done to the 2.5 and where would I find more information on such a thing?

 

I would think the gas mileage is about as good as it's going to get. This is a 4.2 litre V8 engine in a lightweight car made of aluminium. Here in the UK we manage to run these cars with petrol (gas) at £1.20 a litre ! Where did you get '2.5' from ? Other engine in 2003 was the 4.2 litre supercharged saloon, and the 3 litre V6 engine as in my car, based on a Ford engine, and probably the best for reliability. Diesel cars came in 2005 but not for the US.

 

Only the 2003 X-Type model had 2.5L. The OP would need to post in the X400 forum.

 

Jlacy, like others have mentioned here, something is awry with what you are saying. You either have an XJ with the 4.2L engine or you have an X-Type (not the same vehicle as an XJ, think of it as the little brother of the XJ since the X-TYpe is a mid-size car) with the 2.5L motor.

In your post over in the other XJ forum, I gave you some good information based on the car you are looking at assuming it is an X-Type. There is a big difference between the XJ and the X-Type. In short, the XJ is a full on sport luxury car with an emphasis on luxury. The X-Type was meant as an introductory car to the Jaguar line and is "bare bones" when you look at the rest of the jaguar line. By no means is the X-Type an option free vehicle with no features. But, simple things like the XJ is going to come with full leather seats where the X-Type is going to have leather on the 2 sections where your butt touches the seat, the rest is faux leather.

If you have questions, please let me know. I owned a 2003 X-Type for 7 years and now own a 2012 XJ. Apples and Volvo different from each other.

 

Actually the X-Type is a compact car, though not germane to the question. The S-Type is mid size for that era.

 

And the S-Type did not have a 2.5 in USA I believe. So, sounds like an X-Type (X400).

The idea of a 2-ton luxury car and trying to get a remap to save fuel? Weird.

 

Yep and the XJ supercharged gets 30 MPG highway.

 

Who's getting 30 MPG in a x350 SC on the highway? Maybe going DOWN the mountain.

 

It's not beyond the realm of possibility. In my XJ8L I was getting 32-34 mpg at around 65 mph. The highest I saw was 35 mpg at 60 mph. However, once traffic raises its ugly head, mileage will suffer.

 

I can get 27 mpg on a 450 mile trip from MD to MA and that includes a mixed bag with some cruising at 85 mph.

 

No problem doing that on the highway cruising at 120kph
In fact I sent it a lot better in my XJR it just depends on the terrain

BTW it gotten better with Cambo's tune but only while cruising

Cheers
34by151

 

What year is your XJR ? Reason I ask is that Cambo can tune the 2006 model for good effect however it sounds like the gain for my 2005 would not be worth it.

If I did not mash the pedal quite as frequently on my long trips I think I could easily make 30 mpg. However I have not got that self control!

 

I have the 04, models with VVT can get some more gain

I can use more than before or less just depends on how I drive.
Im rarely in traffic which makes a big difference and most of the roads flow at 100Kph or more. Then again Im not in the city

I have seen it as low as 6.5L/100km but average 8L/100Km on the highway. On the track you can double that or more but Im not looking at the fuel efficiency


Cheers
34by151

 

Right. I do not have VVT.

 

I did, easy and often in my 05.

 

Are these figures tank to tank top up or instant readout figures, my ‘99 XJR is struggling to get anywhere near 25 imp mpg?

 

I keep track of the consumption using both Trip A and B
I reset Trip A per Tank and leave Trip B for long term

Im guessing you would be around 12L/100km in Auckland given the the hills and 14-15 on trips

Cheers
34by151

 

This is an entirely different class of vehicle and apples to oranges. The X350 went all aluminum body and the SC got better mileage than the N/A.

I won't speak for others but mine were readouts - instant. And average was of course less but still 27mpg. Highway driving (long trips) was always 30 average. I averaged 70 mph speed and used cruise control

 

My figures were average over a 450 mile trip. Not tank to tank top up.

What is interesting, to me at least, is the SC car has a very inefficient compression ratio at low speeds and does not really become more efficient until the SC is running at a decent clip.

 

Other way round but yes roughly correct at present.