We've already tried the entry-level 197hp version of the Mazda CX-60's e-Skyactiv D MHEV diesel engine, at the international launch earlier this year. 

We found that version to be torquey (450Nm), especially low down the rev range, and efficient, but not that quick with 0-62mph acceleration in 8.6 seconds. 

This time we've got the most powerful 250hp version, with 550Nm of torque - a substantial increase over the 197hp version. It also has a 48-volt mild hybrid system and is driven by eight-speed automatic transmission.  

Other manufacturers might be moving away from diesel, but with this clever engine, which has an unusual piston design and fuel injection technology called Distribution-Controlled Partially Premixed Compressed Ignition (DCPCI), even in its most powerful form, it proves to be impressively efficient. This cleverly offsets the impact of this engine's size and friction, keeping the engine in a closely controlled, lean-burn state for longer. 

The result of all this is an engine that can operate at better than 40% thermal efficiency for much of the time. This proved to be correct, as our test car stayed in the mid-thirties for mpg during the week we had it on test, and we believe that this could be easily improved by being a bit more careful with how you drive it. The 138g/km CO2 figure for this Mazda seems low considering the engine size, too. However, the 32% BiK figure will be far harder to stomach for company car drivers.

We had the range-topping Takumi version for our test vehicle, which includes niceties such as white Nappa leather trim, white maple wood trim, heated front and rear seats, power tailgate, excellent Bose sound system and head-up display. The drive position is comfortable, and all the seats are supportive, with a practical 570 litres of boot space - the same as the PHEV. Mazda told us that it expects 87% of CX-60 diesel customers to choose the 250hp model - although not perhaps in Takumi spec. That white Nappa leather trim doesn't look very hard-wearing, as our test car was just a few thousand miles old, and the driver's seat in particular already looked dirty. We think the lesser-spec Homura might be the better option. 

While this CX-60 diesel has 450Nm, it feels disappointingly slow from the off, thanks to the wooden throttle response. It gets better in the mid-range - but it never feels that fast. The 0-62mph acceleration comes in 7.4 seconds. 'Sport' mode doesn't seem to make much difference either, although the throttle is more sensitive, but in an era where we're moving away from the ICE engine, the six-cylinder soundtrack sounds great.

On the road, the most powerful CX-60 diesel isn't as nice to drive as its lower-power two-wheel drive brother. The steering remains precise, the CX-60 is a tidy handler, we like the rear-drive bias for the four-wheel drive system and as you expect, grip is still good. However, the ride on the Takumi's standard 20in wheels is crashy, unsettled and plain noisy on anything other than the motorway.

The brakes too, remain easier to modulate compared to the plug-in hybrid version. But like the 197hp version we drove previously, again we experienced noticeable drivetrain shunt, from the eight-speed gearbox.

So, the CX-60 diesel's efficiency impresses again, even in the most powerful version, but the higher BIK figure and the general move away from diesel power for company vehicles, will, we think, still make this Mazda a tough sell in the UK.