I used to do this whenever driving down through France, which is how I know you are on the same consumption as me!
Also proved an auto TD5 drinks more than a manual 300tdi!
But when towing a large box trailer, with the Cd factor of a block of concrete, consumption figures made me cry, nearly!
Discussing fuel economy nearly got me beat up a few years ago.
Me: Citroen ZX TD
Cousin: Volvo 760 saloon 5.7L Chevrolet V8 (ex Cliff Richard car)
Me: fill up tank
Cousin:fills up tank.
Both drive down to Brands Hatch from Redditch, cousin towing a two birth caravan for our tame racing driver's elderly dad to stay in over the weekend.
We have to stop for cousin to refill tank on the way.
Arrive Brands Hatch. The two cars we looked after race.
Exit Brands Hatch after tipping unused race car fuel into Volvo. Drives to first available petrol station, Volvo tops up.
Drives back to Redditch, having to stop on way to refill Volvo.
Arrives back in Redditch, i drive home to Bromsgrove.
During the week we both drive around as normal, to and from homes to work etc. Cousin has to refill during week, i don't. The next weekend we are racing at Croft, Darlington. So early saturday morning i met up to join the convoy north. Cousin had topped up the Volvo again the night before, and off we went. Volvo again towing the two birth and again stopping on the way to refuel the Volvo. Me? I just drove using the same fuel i put in before Brands.
Sunday afternoon after racing he's there topping up the Volvo with unused race fuel. I casually remark to my cousin that i think i'll have to fill up when he does as i don't think i'll quite be able to make it back with what i've got.
He makes some comment about having suspected i was 'full of sh*t' about how economical my car was on fuel.
I asked what he meant?
"You can't even get from Bromsgrove to Croft and back on one tank!"
I started to laugh. "No mate. I can't get from Bromsgrove to Brands Hatch and back, then drive to and from work for a week and THEN drive to Croft and back!" At which point i legged it until he'd calmed down!!!