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I've got a very late 2011 C30 D2 1.6 DRIVe, 2012MY, SE Lux. Stacked with options. I've had it performance remapped and it is actually quite spritely. I put new Bilstein OE shocks on it, not 'sport' anything and it handles really well. It is after all a Focus chassis which has the reputation of being a real goodun.
The other day I zeroed the consumption and did an 85 mile run, 25 miles urban/rural and 60 miles Mway. Was not trying to drive economically. Here is what I got.
I agree you won't get 80mpg, but you'll get up close to 70ish. Pottering about mine never goes below 60mpg.
Thing with the remap is the substantial torque peek is at 1,900 rpm, which is 60mph in 6th. On an Mway you can boot it, in 6th, no down change, and it cracks up to 80-90 effortlessly. If you are doing 84 miles a day Mway it WILL return great mpg. And as posted VED is £0.
If you fill the tank and look at the 'range' it is often up at 780 miles.