Years of unadulterated diesel propulsion have come to an end as Toyota has equipped its latest high-spec Hilux with a hybrid powertrain.

Yet this is no ordinary pairing of combustion and electricity. Because rather than the typical approach of adopting a petrol block, Toyota has kept its 2.8-litre turbo diesel in play.

The result is the mildest of mild hybrids, whereby the engine functions as it normally would – from the driver’s perspective at least.

See also: On test: Nissan X-Trail gets new practical hybrid powertrain

Meanwhile, a combined motor/generator and 48V lithium-ion battery beaver away in the background trying to boost performance and bolster fuel economy.

Currently, the top-of-the-range Invincible X with automatic transmission is the only model to feature this setup, while both the manual and lower-spec Invincible models continue running straight diesels.

So, is it an improvement, or needless extra complexity? Well, it depends on the type of driving it’s going to be doing.

How fast is it?

As the engine is assisted by a motor and battery it would be logical to assume that there’s some zestier performance to enjoy.

But this isn’t quite the case. Outright power and torque are the same as its predecessor at 204hp and 500Nm, and acceleration isn’t any quicker either.

Instead, Toyota says the hybrid system puts its efforts into refining power delivery.

On the road, there’s a promise of more linear acceleration and controlled deceleration from the regenerative braking system.

Off road drivers get smoother throttle response and safer descending on steep slopes.

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This does work to an extent, as it feels sprightlier than the cold, hard facts of the spec sheet would have you believe.

If Toyota published a 0-20mph time, there’s a reasonable chance it would have a Top Trumps winning stat in its favour.

Still, this isn’t much help when competing against V6 rivals from Ford and VW, which have 40 more horses under the bonnet and 100Nm of additional torque.

It’s a similar situation when squaring up to the new plug-in hybrid Ranger which offers 275hp and 690Nm, plus the option of driving 26 miles on electricity alone.

What about fuel economy?

There aren’t big benefits to be found here either, but some drivers could see improvements.

Long-distance cruisers have the least cause for celebration as there’s minimal deceleration to harvest energy from, or opportunity for the more efficient stop-start system to come into play.

In fact, the combined cycle figure of 27.9mpg is actually slightly lower than it was in the regular diesel.

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That said, our test vehicle comfortably bettered this mark, achieving 33mpg during a week of mixed driving with a couple of lengthy jaunts.

More likely to see a reduction in their fuel bill are drivers that spend a good portion of their journey stationary.

Typically, this will be in urban environments, but it could apply to some sorties around farms and rural areas.

In these situations, Toyota reckons drivers could see fuel economy improvements of up to 5%. Far from startling, but better than nothing.

How does it work?

It might sound like engineers have added a lot of extra complexity to achieve these modest gains.

But the hybrid system on the Invincible X is essentially a fancy starter motor; one that can both generate power from the engine and feed it back when required.

This is teamed with a small 4.3Ah lithium-ion battery pack housed under the rear seat that weighs just 7.6kg.

Once fully charged, its cells deliver up to 12kW of power and 65Nm of torque to the powertrain.

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In addition, the fact that it’s far more powerful than a conventional starter motor means it fires the engine faster and allows it to be stopped for longer periods.

Naturally, there are a few more electrical components than a conventional setup, but these have been waterproofed so that off-road performance and fording capabilities aren’t affected.

Buyers can also take comfort in the fact that Toyota is a dab hand in this game. It’s been building hybrids for decades and, for the most part, they’re pretty reliable.

What about off-road performance?

Just like the regular Hilux, the hybrid has a two-range transfer box that delivers four-wheel drive, with a rear diff-lock available should some extra traction be required.

But this is the first example to feature the firm’s Multi-Terrain Select (MTS) system, which allows drivers to adjust vehicle stability control parameters according to conditions.

Like before, the truck is able to automatically juggle settings to find grip, but it can now be pointed in the right direction by selecting one of five pre-set modes – dirt, sand, mud, deep snow or rock.

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Other stats of note include 310mm of ground clearance, respective approach and departure angles of 29 and 26 degrees, and the ability to wade through water up to 700mm deep.

Toyota also reckons the system makes off-road driving easier, largely because it has a 20% lower idle speed that gives greater control when negotiating obstacles.

This is a sensible enough claim but, in the real world, most people aren’t going to notice.

What’s the interior like?

This generation of Hilux has been around about a decade now and the interior is showing its age.

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Not necessarily in a bad way though. Buttons and dials are abundant, making it easy to find most functions.

And the central display, albeit small by today’s standards, is sharp and works with CarPlay and Android Auto.

As the top spec model, the Invincible X’s finish is suitably plush with leather seats and piano-black trim, but it’s tough and utilitarian enough to weather working life.

Verdict

Whichever way you cut it, the efficiency gains from the new hybrid system are marginal at best.

Only those people that do a lot of stop/start driving are likely to notice a difference at the pumps and that’s assuming they have it fully active so that the engine turns off when the vehicle is stationary.

It’s the same story with performance, although the smoother acceleration is a bonus and it does seem quicker off the mark.

Perhaps Toyota should have pushed the boundaries a little further, like Ford has with its plug-in hybrid Ranger.

But even though the benefits of the hybrid Hilux are slight, there aren’t many downsides to shoulder either.

That’s just as well as, for the time being at least, it’s the only option for those seeking a 2.8-litre engine and an automatic transmission.

A new generation Hilux is expected soon, but we’ll have to wait for more details of the powertrains that will be on offer.