Should I buy a 1.9-litre or 3.0-litre 2025 Isuzu MU-X?

If you're looking at buying an Isuzu MU-X, now is the perfect time. You can either grab one of the runout 2024 models or jump into the new 2025 facelifted model.

With the addition of the 1.9-litre engine to the MU-X line-up in 2024, determining which is the best option for you can be a bit confusing.

Having driven both engine powerplants in the 2025 Isuzu MU-X, I'll explain everything you need to know before you decide on an engine.

The Isuzu 3.0-litre turbo-diesel is part of the 4JJ engine family that Isuzu is famous for. Australians have had a long affection for this powerplant for over 20 years, and it has been the beating heart of the D-Max and Holden Colorado since 2003.

The 3.0 has undergone several changes, and as of 2021, the D-Max and MU-X are powered by a 4JJ3-TCX. The engine size stayed the same, but the block, cylinder head, and surrounding components were revised.

Before it was installed in a car, the new engine underwent countless bench tests and more than four million kilometres of durability driving.

Interestingly, Isuzu is now mostly an international commercial and light truck manufacturer. These engines weren't just built to putt around the shops with; they're over-engineered to haul equipment and handle stop-and-start situations.

The 4JJ is the choice for Isuzu's tipper and loader trucks, which seem to dominate the road in that category.

The forums don't seem to have anything bad to say about the four-cylinder in terms of complaints online. The only major ones concern the exhaust gas recirculation (EGR) and diesel particulate filter (DFP), which is a common issue among all diesel engines that spend their days at slow speeds.

These components need mid- to high RPM to clean out the carbon in the EGR, while the DPF needs to occasionally be taken on longer journeys to perform cleaning processes.

But, the 4JJ is a cult and legendary motor, and is often heralded as one of the best turbo-diesels of the modern era, with its popularity making it easy to maintain and find parts for.

The 1.9-litre turbo-diesel RZ4E-TC was introduced into the D-Max range in 2019 before making its way into the Isuzu MU-X for 2024.

While the RZ4E doesn't have the same cult status as the 4JJ, it has still proved itself to be an excellent engine.

When it comes to engines, previously it was thought that the bigger the engine, the more reliable it would be – since it can be a little bit more lazy and have large tolerances while putting less stress on internal components.

But we have come so far with manufacturing, and Isuzu has put all that into the RZ4E. Previously only found on high-end sports motorcycles and supercars, the RZ4E utilises what is called DLC (Diamond-Like Carbon) in tandem with a graphite coating on the pistons and a nitrided carbon steel crankshaft.

All this translates into stronger internals and less friction, meaning the engine doesn't need as much fuel and oxygen to run efficiently and reliably despite its high output and small size.

The RZ4E has yet to receive any major complaints about reliability from its owners. The only recall was due to a faulty engine module that was quickly replaced, yet the mechanical components of the engine have seen many people praise the little motor.

Again, like other diesels, the EGR and DPF have caused some issues, most likely in city-dwelling cars.

Both engines are proven reliability merchants, making the decision between the two much more difficult. At the end of the day, it'll come down to what you need in your vehicle.

It's worth noting that depending on the trim level you want, you may not have the choice. If you want all the extra gadgets, you'll have to opt for a 3.0-litre, as the LS-T and X-Terrain flagship models only come with the bigger option. But luckily, you have the choice between the two for all others.

Consider your lifestyle. While the 1.9-litre option has an impressive tow rating of 3000kg, the 3.0 increases it by another 500kg, topping out at 3500kg braked. If you're towing a particularly large caravan or boat, it may be the better option to purchase a 3.0-litre.

If you're fuel-efficient and eco-minded, the difference between the two in fuel consumption is noticeable. Isuzu claims the 1.9-litre uses 7.4 litres of fuel per 100 kilometres for either 4x2 or 4x4 models, while the 3.0-litre uses 8.3L/100km – that's nearly a 12 per cent saving.

Fuel isn't the only saving; the 1.9-litre engine costs $2000 less across the board for both LS-U and LS-M 4x2 and 4x4 models.

Perhaps the biggest decider between the two is the fact that the 1.9-litre is down 30kW and 100Nm over its 3.0-litre big brother.

If you are performance-minded, it goes beyond the factory power specifications too – the 3.0 is a bit of a lazy motor for good reason; it means that it's not under as much stress. But when you look at the power specifications of this sub-2.0-litre engine, it seems pretty impressive, which can sometimes mean the engine will be under more strain.

Your deciding factor will depend on whether you value emissions figures, fuel economy, and purchase price over more power and more towing ability. You're winning with whichever engine you pick.

After spending two days driving both powerplants, I can wholeheartedly say the 1.9-litre is impressive in keeping up with the 3.0-litre.

Both engine sizes could handle rough terrain, and you will have absolutely no worries when it comes to general daily driving.

The 1.9-litre is noticeably down on torque, but it doesn't feel like a 100Nm difference. Isuzu has most likely mapped the throttle response to be more aggressive on the 1.9 to close the gap in power between the two.

I did not get the option to tow with the 1.9-litre, but again, while it can tow three tonnes, I would opt for the 3.0-litre if I were to do a lap of Australia or consistently needed to have my caravan hooked up.

Peak torque on both models is available at a similar range: 1600–2600rpm for the 3.0-litre and 1800–2600rpm for the 1.9-litre, meaning the grunt you feel when you stomp on the accelerator is similar.

If I were to buy a new Isuzu MU-X, I would still prefer the 3.0-litre, but I wouldn't be disappointed with the 1.9-litre either.

Zane Dobie comes from a background of motorcycle journalism, working for notable titles such as Australian Motorcycle News Magazine, Just Bikes and BikeReview. Despite his fresh age, Zane brings a lifetime of racing and hands-on experience. His passion now resides on four wheels as an avid car collector, restorer, drift car pilot and weekend go-kart racer.

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