Actually, 75 to 77 mph regardless of the vehicle. She sets the cruise control just below the threshold where the Highway Patrol will pull you for speeding on I-95....

 

No doubt she has the hands-off phone working overtime yapping with her mother non-stop.

 

Yep, and listening to Books-On-CD at the same time. And probably doing something on her iPad as well....

 

Xeno, I'm not sure where you got those EPA numbers and for what model year but comparing 2008 S-Types side by side the results are
3.0L- 17 city/26Hwy/20 combined
4.2 L- 16 city/24Hwy/19 combined
4.2R- 15 city/22Hwy/17 combined

Generally a smaller displacement engine will produce better fuel economy than a larger engine in the same vehicle body as long as the engine is not grossly underpowered, which for the S-type, it is not. Speaking personnally my 2000 3.0L SE model has a lifetime fuel economy average of over 28 mpg over 104K miles . On long trips I have a best tankfill of 36.6 mpg and many 30mpg+ tankfills. S-Type are very efficient for their size and weight if driven correctly.

Driving style, tire pressures, and vehicle condition are important factors for achieving good fuel economy.

 

Xeno used the figures originally issued under the old rating system. Yours use the new rating system. Apples and oranges. If the old are converted to new, they're pretty much the same year after year.

EPA numbers are of very little value in the real world- but that's another topic.

 

You guys are making me jealous with your 20's mpg results. I'm in Atlanta and do 100% surface street driving (no highway in my commute at all). My average speed is 17 mph and my fuel economy is at 13.6 right now. The really depressing part is when I have enough road I'm usually driving 45-55 so I'm spending ALOT of time sitting. It takes me about 45 minutes to complete a 10 mile commute.