EVEN Mitsubishi must have been surprised - and more than delighted - at the way sales of its big plug-in hybrid Outlander PHEV took off, with more than 20,000 in British roads today.

Part of its success, in the early days at least, was a clever decision to charge the same for the cheapest version of the petrol/electric hybrid and diesel Outlander.

Add in the tax advantages of choosing the Outlander with a big battery in the boot and an electric motor to give some pollution free miles before the petrol engine kicks in and no wonder it sold so well.

It rather put the diesel in the shade, even if this version could be had with seven seats - a family friendly feature denied the PHEV because its battery took up space in the back.

But there's good reason to look at the diesel if you don't fit the profile of an owner who could get the most out of the part-electric Outlander; if you do a big daily mileage or don't have ready access to a charge point, for instance.

Now there's another financial reason to check out the diesel too; that price parity is gone. The cheapest Outlander PHEV now costs a cool £6,950 more than the least expensive diesel in the price list.

The gap narrows as you pile on spec - the diesel on test is a top GX4 version and there's around half that difference between it and an equivalent PHEV, after the government's £2,500 plug in car grant is included. You could buy a lot of diesel for that.

To complicate matters, Mitsubishi will give you £2,500 deposit contribution if you take a an Outlander PHEV on a finance deal - cutting the price difference between diesel and hybrid to the same £1,000 it was all those years ago. Got it?

All versions of the Outlander have been given a thorough makeover in recent months, with the usual mid-life cosmetic changes (new grille and bumpers included) but changes more than skin deep.

Dozens of small changes, from thicker glass to more sound damping, are aimed at cutting noise inside the Outlander's spacious cabin, itself upgraded with new fabrics and more plushly padded seats. The top models have black ash inlays on dash and doors, intended to add a touch of class.

Underneath the car there are subtle changes to the suspension, designed to improve the ride and sharpen its response when you meet a corner.

So, fair to say Mitsubishi is intent on keeping its big 4x4 in showroom contention.

And it's produced a car that still feels honest - read that as robust and sturdy rather than catwalk svelte - but is usefully more pleasant to drive or be passengered in.

On the right road (smoothish, straightish) the diesel Outlander actually motors along with the sort of refined comfort you might expect in a big saloon, not something that will switch to four-wheel drive in an instant when you're crossing a muddy field.

Those third row seats are big enough for a couple of smallish adults and with them folded away into the floor (most of the time, probably) there is masses of luggage space.

But what about the economy? Well, the Outlander showed a little over 41mpg after several hundred miles. The dearer PHEV model will go several miles on cheap electricity alone, but on longer journeys its petrol engine won't match the diesel's frugality.