I don’t understand what you describe as “well know for dirt” and “signs of trouble ahead”. I will assume the garages mean choked EGR systems. You could try some of this:

http://www.powerenhancer.co.uk/product.php/3/bg-244-diesel-fuel-cleaner

(I have no connection with the company or product other than as a customer).

Do you really mean 36,000 miles a year! That’s impressive. I can’t see any car doing that every year is going to be low maintenance; that’s three services for most cars. Then there’s tyres, brakes, even the “reliable makes” require them. You don’t specify budget. Plenty of others will be recommending the usual suspects. It’s serious medium diesel territory; one with a decent seat and reasonable servicing costs would be my priority…or get another job!

Edited by dereckr on 12/07/2011 at 00:35

What sort of budget are you looking at it would help people give suggestions. The stories about the engine "well known for dirt" is a new one on me but i would say those 1.4TDCi units in the Fiesta's are pretty useless for regular motorway driving, very low power output, has to work very hard if its doing 36k a year, i would say to change the car now.

Theres plenty of alternatives, you can get a good Focus TDCi for 3-6k odd, i'd recommend the 1.8 as its very economical and enough power to be comfortable on the motorway, Zetec trim level may crash about a bit, Ghia is probably better but most of the diesel Focus' have done high miles, its difficult to find a low mileage good one but you could get a petrol one with decent economy with less miles probably for less money.

I know the OP specified small cars but Im seeing 4-5 year old TDCi mondeo's with pretty low mileage (seen a few with under 40k on them) the 2.0TDCi's for 2-5grand, very comfortable motorway cruiser, will feel alot more at home on such roads and the diesel units give good economy, if anything better economy in the bigger engines. Anything less than the 2.0 in the Mondeo is underpowered in my view as its a big car. For similar prices im seeing Peugeot 407 HDi's with excellent economical units, long service intervals etc. Generally you can get a better deal and more for your money on something like this than a Focus.

I think one of the few things unthrottled may back me up on is that a car runs at its most efficiently when its in constant use. 20 thousand consistent motorway miles does less damage, wear and tear than 10 thousand pottering about town in my view. In general i'd steer clear of the smaller engines for such a heavy workload.

Edited by jamie745 on 12/07/2011 at 01:28