Gas Mileage and Supercharger Engine Longevity

I''m pretty much sold on the new XF. I''d never thought I''d own a Jag, but this car will be the perfect replacement for my Lexus GS 400 with 220,000 Miles on it.
 
My current GS is very similar to the XF in that it is rear wheel drive and has a 4 liter over head cam V8 with variable valve timing.  My lexus gets 24-25 highway and since I drive mostly highway I get a combined 23 mpg which is ok for me even with $4 gas.
 
My first question is, what type of highway mileage have new owners been getting with either the normally aspirated or supercharged version. The reviews that I have been reading seem to indicate the mileage of the supercharged version is way below the EPA rating of 23. For the supercharged car, USA today averaged 13.6 in mixed hwy/city driving, and Motortrend averaged 14.8 mpg during their tests(they did not say hwy or city).
 
My second question is I am looking to get a sense for what the longevity of the supercharged jag engine has. I test drove the supercharged and the car is a blast, but I am concerned that any Forced Induction engine will not last as long as a normally aspirated engine. What is the longevity I should expect on a supercharged engine if run 90% hwy miles? My current Lexus has 220,000 miles on it and does not burn any oil. I change my oil with Mobile 1 every 3-5000 miles. If I could expect the engine to last 150,000 to 200,000 miles I would go for the supercharged car, if not, I''ll go with the standard engine.
 
Thanks for your input

I can answer gas mileage, not about engine life.
 
With new car under 1000 miles on it, city is 11 mpg and highway is 18.6 at 75 mph.
 
But on the otherhand, you don''t buy a Jaguar or supercharged engine to get good mpg.
 
The car is absolutely fantastic with everything standard.  But if you are looking for lowest cost and super reliability, go for  the Lexus.

You don''t but a Jaguar for her awesome fuel economy that''s fact and I agree . Well, on the other hand related to the supercharged engine lifespan , XJR''s engine requires some special maintenance at the certain mileages to the  best knowledge of me considering XFR comes with the supercharger ,  it might require similar attention though XJR and XFR are totally different beasts .

XFR and XKR have the same engine, transmission and suspension. The brakes are probably very similar and the wheels fit either car. The body is different, duh.
 
I get fuel economy as good as 8 l/100 km on the highway at 120 km/hr which is outstanding for a 4,000 lb 4.2 liter automatic car. This is 35 mpg Imperial or about 28 mpg US. I get around 16 l/100 km around town, sometimes better, which is around 17 mpg Imp and around 13.5 mpg US. I have only 5,500 miles (8800km) on the car and mileage is steadily improving as the engine continues to loosen up.
 
The performance of the normally aspirated XF is sufficiently good to make the SV8 version overkill IMHO. 0-60 takes around 6 seconds as compared to around 5 secnds for the SV8 version. In the real World a 0-60 of 6 seconds is ample.