Maintenance is key.

I drive my 4.2 SC every day and am averaging 17.2mpg currently and do 20 miles a dya to and from work with one bit of dual carriage way for 1 mile and the rest is A roads in traffic.

Have had 23mpg out of mine when I drove it to Czech Republic and back a couple of years ago.

Never driven a TDV8 at all so can't comment, but I only do around 6,000 miles a year so the SC is a no brainer for me

Enjoy your new car

cheers Alex

2018 Skoda Kodiaq vRS
2009 Caterham Supersport Race car
2007 M5 Touring
2005 Range Rover Vogue SE Supercharged
2004 SL55 AMG

Staying below 70 definitely helps. My 3.6 TDV8 returns 37 to the gallon if I keep the cruise control set at 60mph. Even though that it's ticking over at 1,600RPM at that speed, I'm still amazed at how much better on a run it is than I would expect for a self-propelled cathedral.