My mileage will be sub 10k per annum, and the difference in economy between the 320 and 220 does not at least on paper seem to be huge. A matter of 4-5mpg only. Is that correct, real world? And I've been trying to figure out what additional std eqpt comes with the 320 over a 220.
I drive a 2007 E320 CDi. I've been driving about in a hired 2008 E220 CDi recently (both Avantgarde), and with fuel consumption, the E220 CDi was only better by 1-2mpg.
A couple of reasons why I think this is, because I generally drove the hire car in a harder way as I was used to the power of the E320. Overtakes, accelerating to NSLs out of villages, getting up to speed on motorway slip roads took a little more effort in the E220.
Coming from an M5 and an RX8, and being used to the power you may be driving the car hard to match the power you were used to, not so much if you bought the E320, and this will probably harm the fuel economy.
Also being a hire car, which had 115,000 miles on the clock, it may not have been maintained as meticilously as mine (it was loaned from a smaller independent firm - not a big one such as Hertz/Avis etc., where their cars are usually not that old) - also felt like it too, air conditioning stank for the first few days I had it (probably been sat around for weeks previously), interior was really creaky - creaks from the door panel, steering column and the dash in general, and I could tell that it's been smoked in. Getting back in my E320 183,000 miler felt like it was being in a new car again! My car felt "lighter" and driving it again, felt like it could really fly. Also the interior in the hire car looked very tired, and the leather on the driver's seat was much more smoother and felt well worn.
Anyway, minor differences between the two, I noted were the 16" wheels (17" on mine), the door panels on the back - mine has storage compartments/ashtrays, while the E220 just had a mesh grille, and the centre console, while both had the UHI phone connector, mine splits in the middle to reveal an upper tray (where the phone sits), and a bigger, deeper lower tray. The hire car just had one big compartment and the phone sits upright on the rear "wall" of the compartment. E220 had a smaller fuel tank than mine, 65 litres/80 litres if I recall from the brochure. I also noticed that the E220 didn't come with headlamp wash. Mine does. Not sure if any/all of the differences were due to the fact that it was an E220/E320, or the difference in model year perhaps 07/08? (though mine could have been an 08, as it was registered in September 2007).
Didn't think the E220 CDi was a bad car, didn't really feel underpowered - just that the E320 CDi is faster in comparison, and as I'm used to driving it the way it is, the MPG in the E220 suffered. Being a hire car in not as good as shape as mine didn't help either - there was evidence particularly in the back that it has been used as a Saturday night minicab, and it probably was.
