I get about that consumption in my 5.0 on mainly short journeys around town. I have found that starting with a cold engine really increases the consumption - if I drive about 5 miles from cold I'll get about 14mpg. If I stop for a short time and then drive back I'll get 18 or 19mpg, so the cold start really gets through the fuel. My overall consumption since I've had the car (August 2013) is 4614.1 miles at 16.3573 mpg - worst tankful was12.7338 mpg, best 24.0282 mpg.

I guess you have the 4.2 so your figures are likely to be a bit different to mine, but I'd think they'd be in the same ballpark. What do you get on a longer run?

 

Interesting, thanks for that.
I don't really know for longer journeys but I'll certainly check it out the next time I go on a run.
So I guess leaving it outside in the winter must suck - would garaging it help do you think?

 

If it helps.....

I have a 2008 4.2 XKR with 40 K on the clock. Sitting in heavy traffic for an hour and a half (the joys of London) I still get 15 MPG.

 

The engine has only just about warmed up over that short distance.You could try resetting the trip meter half way on your journey and that will take out the really cold start data.

Could also be a thermostat as you can't see the water temp. I am sure it must have one. It has done 115k miles

 

Thanks for the info guys, appreciated.
woo5ie - do you mean the thermostat may be faulty?
I have an OBDII reader that gives me the oil temperature - would this give any clues?

 

I assume that the XK has a thermostat but you can't see the engine temp as there is no gauge.
If the stat was opening too soon or stuck open then it could run a bit too rich.
how would you know on these cars if the stat was faulty. Can you tell on the OBDII reader

but check the trip first by restarting after a few miles or stop and restart the car which also restarts one of the three trip totals it's the Auto trip that resets every engine start.
In my XK I regularly do a 12 mile journey with very few stops or traffic that shows around 25 mpg. If I stop and restart the car after the engine is warm the shown mpg increases to 30 ish

 

There is a thermostat, had mine replaced on last service.

 

I drove a couple of miles from work to a quick 3 minute stop.
I then jumped back in, reset the trip and drove for around 10-15 minutes at average conditions (except a short punt of fun joining a dual carriageway).
Low and behold when I got home the Average MPG had climbed to 20.
By the look of it, the advice about the engine being cold is true.
Would it make a difference if the car was kept in a garage and a bit warmer or is it simply the fact that the engine takes a time to warm up naturally?

 

Unless the garage is heated, I suspect the engine will be pretty much as cold after an overnight in the garage as outside. Do you have an Auto setting on your trip as well as an A and B? If you do, the auto trip will reset every trip to save you bothering to reset it.

 

Have just spoken to these guys:

KENLOWE

They appear to make a system that keeps the engine warm by heating the water and keeping it circulating around the system.
Apparently not very tricky to fit.
Including delivery and VAT it comes to just over £300.00.

I guess the question is, will I save more money in fuel and potentially less wear and tear than it would cost to buy and fit?
Any thoughts guys?

 

Looks like it's a 2KW heater. Assuming you have it ONovernight and assuming it's thermostatically switched ON for half that time thenmy guess is that I'll will cost about 1 pound per day. So I doubt it'll pay foritself in fuel benefits anyway.

 

Apparently you just put it on a timer and have it come on an hour before you intend to drive.
Hopefully this won't be too much of a drain on the electric bill and a will make the MPG a little less depressing.

 

Ahh ok so it'll probably cost about 20p per day.

Just for fun : for me with a one way 16 mile commute I get 27mpg. I expect I'd get 30mpg with a warm engine.

'Cold' Costs outward assuming 6 quid a gallon: 16/27=0.59x6=3.54pounds
'Hot' Costs outward assuming 6 quid a gallon: 16/30=0.53x6=3.20pounds

So I's save 34p-20p=14pence per day! (I expect the difference would be bigger going across town - I get 14mpg on a cold engine but nearer 20mpg with a hot one)

So your outlay of 300 quid would take me 2142 days to pay for itself.
Or buy a Diesel…..

 

Or buy a Diesel…..

Great advice for someone who drives 5-10 miles a day.

 

I get you completely, and thanks for breaking it down.
I may still look at doing it as I hate the fact that the car feels cold when started.
I know that sounds daft but knowing that things are hot when you start does allow you to enjoy the short journey more than trying to look after the engine until it gets warm.
I just need to find someone competent to fit it.

 

Your mpg figures around town sound about right. It doesn't sound like there is anything wrong with your car. Short journeys are not good for any car so should be avoided. This coolant heating device sounds like a con to me - you don't want to be heating coolant up to get the engine to operating temperature, its the oil you want to be heating up as it lubricates best when its warm, hence why only ever doing short journeys is bad news.

 

I have to admit I thought the same thing.
To me it would be the oil that needs heating.
I did find another product that is bonded to the oil sump and heats the oil directly.
Seems a bit more agricultural but may be a better option.
I may just stick the car in the garage to see if that makes any difference, especially over the winter months.

 

Hmm, reading this does make me think long and hard about the difference's with the XK and XKR. When looking to buy one this car would be my daily driver. With my current 58' 350Z I do around 23mpg on average and I've heard on here and elsewhere that they can fairly easily on non-stop/start runs go to around 28-30mpg (any truth in that?). I can get the Z up to 28 but its hard to keep it there, but the XKR doing 14mpg?? on average daily driving... that's bad. I know its a 4.2 V8 but its reasonably modern car and though it'd at least stay around the 20mpg mark. Food for thought I think. I know its a bit 'petty' when looking at such a car but 14 is ...maybe too much for me. Might just set my sights on an XK lol.

 

It really depends on the circumstances. My daily commute is a little over 4 miles each way and I see about 19 mpg from cold. However I average maybe 40mph over this distance. If it was stop/start traffic it would certainly be nearer the 14mpg mark.

 

OK I re-read your original post, if you have a failed cat then that may negatively impact fuel consumption. Mid to high teens around town from cold sounds about right for a 4.2 XKR though. Get the cats replaced at a reputable Jaguar independent specialist and don't bother with this coolant heater etc. I wouldn't bother with an oil heater either, they are designed as you say either for agricultural use or for people in places like northern Sweden or Norway who have months of sub zero temperatures.

If urban fuel economy is a concern then this isn't the right car for your commute I'm afraid. I don't say that to be harsh, just that these are by, no stretch of the imagination, economical cars. Doing almost entirely short trips around town is also no good for the battery; all the electrical equipment in the car drains power and short, urban trips don't give it a chance to charge up so unless you routinely use a battery conditioner you're likely to experience some of the common symptoms of bad battery condition.

 

I have had my 07 XKR for just over two years now. Apart from two cross country trips and a day at the drag track, the car spends most of its life travelling 4.5 miles to work and back again through reasonably light city traffic. It has averaged 17.25 mpg in that time.

My non supercharged 4.2 X350 averaged 20.23 mpg and that used to get more longer trips because I could actually fit my family in it!

Those figures are based on distance travelled and actual fuel purchased rather than the trip computer.

 

I ran a 4.0 2001 XK8 and a 4.2 2004 XKR and found the R was about 2mpg worse than the 8 for the same sorts of journeys. My overall consumption in my 2010 XKR is the same as the 2004 XKR, again for the same type of use.

 

I have averaged 26mpg over the last 2 months, though only the first 2 weeks were a city commute (7 miles, average 30mph).

I bought it specifically because I was retiring, and wouldn't be commuting any more.

I don't know what mpg it gave me for the commuting, but I do know I hated leaving it in a multi-storey to be dented/scratched by careless commuters and people who don't know how to park properly.

Since then it has been a mix of motorway and country road use: The XK excels at both!

 

You obviously missed my as well!

 

I currently do around 30miles, 5 days a week. Most of that on motorway. Maybe the XK is the one I should focus on, since 300hp is still... Nippy lol I can always fit a quad exhast system I suppose... Lol I'm not sure why I'm that concerned over fuel as my current 22-23mpg isnt exactly... Tremendous and £30 can last just two days depending what i'm using it for lol... But the xkr's economy seems to take it into a whole different ball park

 

Again, if an XK/XKR is to be your only car and fuel costs are a concern, think carefully before you take the plunge. Rewarding? Yes, definitely. Frugal? Absolutely not.

 

It is perfectly true that they are not exactly frugal, but I think that people overemphasise that aspect of the cost of ownership. It is the one cost that everyone talks about.

With high end cars unless you do a very high mileage depreciation is highly likely to represent a larger proportion of the cost of ownership. The XK is actually appreciating at the moment.

Servicing and reliability are also significant, and the XK fares well here.

Years ago I had a 16mpg Range Rover which overall cost about half as much to run as the more "economical" vehicle it replaced, simply because the previous vehicle was depreciating far faster.

 

Agree - I was worried going from a 37mpg to a 26/27mpg XK for my 30 mile daily commute but the extra cost is only the same as a couple of coffees and a sticky bun bought at COSTA once a week.

Its much harder living with the crappy stereo - I would happily give up 2mpg for a decent media system.