Hi Alan,
I previously owned a C-class 270 CDI - 5 cylinder diesel producing around 180+ bhp and 400+ NM of torque with a 5 speed automatic gearbox - and was Euro III emission compliant.
Solo - and depending on the route - around 45 to 50+ mpg, and 30+ towing a 1200 kg Eriba (but these are much more aerodynamic than the usual white shed)
Now have a E320 CDI with the new 235 bhp V6 diesel and 550 NM of torque - and yes - it's much better, as is the new 7 speed automatic gearbox - and is Euro IV+ compliant
The E-class weighs around 1880 kg with a max tow limit of 1900 kg (2100 kg for the estate) and uses a bit more fuel, solo around 40 to 45 mpg, and towing 1200 kg achieves around 30 mpg - but this is very route dependent
Note: If you are planning to buy an E-class more than 2 years old - then the E320 will be the old straight 6 Euro III engine and 5 speed gearbox - about 190 bhp and 440 NM torque. In terms of power and drive-ability, this performs similarly to the new E280 CDI and the C270 CDI. Fuel consumption from the older E320 is worse than the new V6 E320
What's the new E320 like towing? With roughly the same amount of power and torque as two Ford Galaxies, how about a 0 to 60 mph time of under 10 seconds - whilst towing the caravan.
And rear-wheel drive means grip and traction are fine.
The dealer network is either good or excellent, but no Mercedes is cheap to buy, nor cheap to service.
Robert