A larger engined car has more 'spare capacity' in normal driving, so doesn't need to work so hard, so when you do need it to work hard, it has that extra in reserve. That's why you need a larger engine. The latest fad for the 'ecoboost' type engines (very small engines, but turbocharged), is the last thing you need.

If you've got a car that heavily loaded that it drops down to 30mph going up the hills, then I'd say you've either got it overloaded (as in over the manufacturers limits, in which case your insurance might not be valid), or that there is something wrong with the car.

It all depends on what type of driving you do in the rest of the year, though. Your current car is petrol, the 1.5dci is a diesel - and modern diesels aren't really suited to short trips or low annual mileage.

So, if you do a reasonable mileage a year (15k or more), with regular motorway/longer journeys, then probably diesel. If you do town driving/short trips, then ideally petrol.

BHP and torque figures can be misleading, because on their own, they don't mean much. You have to factor in the vehicle's weight, and the gear ratios too.

Engine size is also misleading these days, as there is a general trend for smaller-capacity engines fitted with turbochargers. As the turbo compresses air into the engine, it enables the engine to produce more power and torque than it would without the turbo.

But generally speaking, a modern turbocharged diesel engine like the dCi in the Dacia will have more torque than a non-turbocharged petrol engine of the same capacity.

So the Dacia should have more 'pulling power' at 40mph in 3rd or 4th gear than your current Mondeo. In other words, the Dacia is (probably) less likely to struggle on long hills.

Have a search for "power versus torque" and you'll find far too much information about the subject.