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  The new diesel puts out 177kW at 4000rpm and 550Nm at 1800-2800rpm, using just 8.3 litres/100km.

Tough-talking Jeep is keeping its word, launching a much-needed turbo-diesel grunter in its top-tier Grand Cherokee.

It debuted the fifth-generation premium 4WD wagon in January, classing it "the most capable and refined Grand Cherokee ever" with a new V6 petrol and the big-bore Hemi V8. Now, it adds a diesel.

Not surprisingly, the Italian-made 3-litre V6 oiler comes from within the family. It's built by VM Motori - half owned by Fiat - and Fiat Powertrain, part of Fiat which in turn owns 52 per cent of Jeep's parent, Chrysler.

Though it is the first time the basic engine has found a volume-production home since its 2004 birth, it has recently been modified and appears now to be a better proposition than the similarly sized Mercedes-sourced V6 turbo-diesel. It is also planned for the Chysler 300C sedan next year.

Jeep Australia calls the arrival of the diesel "the icing on the cake" for the Grand Cherokee. Jeep spokesman Dean Bonthorne says Australians preferred a torquey, fuel-efficient diesel in this category and that this engine "has exceeded all expectations". He says the diesel - now on sale - will grab up to 60 per cent of Grand Cherokee sales.

But he says Australia has been crippled by poor supply of the model. "We could have sold three or four times the number of Grand Cherokees this year," he says of the 617 units sold year-to-date to May. "We have lots of stock coming through over the next couple of months and then you'll see big sales - I think double or triple because of the new diesel."

Bonthorne says diesel versions of the past Grand Cherokees were the biggest sellers and bcause of the features of the new engine, that trend would increase. He says the new diesel gets significantly improved performance and economy because of the Fiat "MultiJet" cylinder head design.

It has 177kW at 4000rpm and torque of 550Nm at 1800-2800rpm, compared with 160kW/510Nm of the previous engine. Bonthorne says it averages 8.3 litres/100km (previously 10.2 l/100km) and has CO2 emissions of 218g/km, down from 275g/km, to meet Euro-5 standards.

Improved performance is matched by an increase in towing capacity. The diesel matches the haul rating of the Hemi V8 at 3500kg, up on the current V6 petrol's 2268kg maximum. The MultiJet system includes a common-rail system with 1800-bar injectors with solenoid valves capable of eight injections of fuel per crank revolution. Jeep says this lowers fuel consumption and emissions by about 2 per cent and reduces engine noise.

The engine mates to the ongoing five-speed automatic with Selec-Terrain traction control offering five modes and the Quadra-Trac all-wheel drive with two-speed transfer case. The Overland model ups the specifications with standard air suspension and the Quadra-Drive electronically-enhanced drivetrain.

Prices for the diesel are $5000 above the 3.6-litre V6 petrol models - the same premium as the Hemi V8 engine. They start at $50,000 for the diesel Laredo, $60,000 for the Limited and $69,500 for the Overland. The diesel is not available in the limited-edition 70th Anniversary model.

If Jeep's 5.7-litre Hemi V8 and new turbo-diesel aren't enough for you, the SRT-8 version is due in a Jeep showroom near you early in 2012. The 6.4-litre V8 (replacing the 6.1-litre) pumps 347kW for a 0-100km/h sprint of 4.9 seconds, topping out at 249km/h.

But treat her gently and Jeep claims its SRT8 will get 13 per cent better fuel economy than its predecessor. That equates to about 14 litres/100km, down from the old 6.1-litre V8's figure of 16.1 l/100km. Fuel thirst is down thanks to a new active exhaust system that lets the cylinder-deactivating Fuel Saver Technology operate over a wider rev range.

Jeep says the SRT-8 can now travel up to 800km on a single tank. If you love the engine but prefer it in a sedan, the 300C version of the SRT-8 is here in the third quarter of next year.