Mercedes C320: 4,700 miles

The numbers whirr round at lightning speed. It’s like watching a fruit machine, except in this case when the numbers stop, there are no winners – just losers. And the only ‘bandits’ in sight are not the one-armed versions, but the oil companies and the Treasury!

The display reads 77.72 – that’s pounds and pence – and it’s the jackpot (or should that be crackpot?) cost of filling up our long-term Mercedes C320 CDI with diesel. What’s more, it wasn’t even a full tank, as there was still just under a quarter left slurping around when I pulled into my local garage.

Over the years at Auto Express I have driven scores of diesel cars, but for the first time I can remember, I am actually questioning the sense of running an oil-burner. And if my E-mail inbox is to be believed, more and more of you are also bemused, angry even, that diesel cars now cost the most to buy and to fill up.

As one correspondent told me - “I accept that buying a diesel car costs more, but what I can’t accept is that it now costs more to run than a petrol equivalent. I thought we were always being told that owning a diesel was more economical in the long run?”

All of this got me thinking. While our Mercedes is a good-looking, comfortable and fine handling car, would we be better off having a petrol engine under that sharp bonnet rather than a diesel? So, I asked our road test editor Chris Thorp to do some calculations (he’s a whizz with numbers and spreadsheets) and compare the C320 CDI to the equivalent petrol model.

Here’s what came out at the end of his number-crunching session: Mercedes claims the C320 CDI can hit 38.7mpg, while the C280 petrol manages 30.7mpg. If you drive 12,000 miles a year, the diesel will save you £239 on your annual fuel bill at current prices. But in Sport trim the diesel costs £2,255 more – so you’ll need to drive it for just over nine-and-a-half years to make the diesel pay! Cover 20,000 miles every year, and the diesel will pay for itself within six years.

Away from the fuel debate, the Merc continues to impress with its grace and pace. I really like the look of the Sport Pack version, and the AMG bits and bobs combine beautifully with the metallic black paintwork and starred chrome grille. The diesel unit and excellent auto transmission combine to deliver real punch exactly when you need it.

Inside the cabin remains classy and comfortable. But I reckon the Merc designers must have been on holiday when the question of storage was being considered – as there’s precious little room to fit anything in the ultra-slim door pockets, the small glovebox or oddly-shaped centre console ‘holders’. A couple of bags of wine gums, a small bottle of water and that’s pretty much your lot! On the plus side, at least the fuel tank is big enough!

Extra Info

Second opinion
There’s a lot to like about our Mercedes. From its sporty looks and torquey engine to the excellent seven-speed automatic gearbox, it makes a great car for an everyday long-distance commute into the centre of London.
There’s still room for improvement, though, because the cabin feels a bit sterile for a model with the price tag and heritage of the C-Class. Some warmer materials, such as wood trim or more leather, would help to lift an interior that’s dominated by plastic.

Dan Strong
Motoring and digital editor