Ask the Guide

A lot of people buying this type of vehicle are horrified the first time they work out their real-world fuel consumption and compare it with the official sticker on the windscreen. Frankly, very very few cars can get anywhere near that official figure. It’s the result of a standard test that bears little relationship with real driving and it’s really only for comparisons with other vehicles, not a realistic idea of what to expect.

Even so, 14 litres per 100km at highway speeds does seem high. Being a 2019 model, it won’t be that the engine is still brand-new and tight, so we can rule that out. But, there are many other factors that affect fuel consumption more than you might imagine. Does the car have a roof rack fitted, for instance? If it does, you can easily use an extra litre per 100km at freeway speeds thanks to the extra drag. And that’s if there’s nothing on the rack (it will be worse loaded).

Is the car carrying a lot of accessories such as a bull-bar, rear step, extra fuel tanks and maybe even a winch? All these add weight and weight kills fuel economy. What tyres are you running? Big mud tyres with an aggressive tread can drastically ruin fuel economy, so can taller tyres than standard which mess up the gearing and force you to use more accelerator pedal than a car on standard tyres. Also, the road from Melbourne to Wagga is mostly freeway with a 110km/h limit. Experience has shown that most cars will give their best fuel economy around the 80 to 90km/h mark, and every kilometre over that sees fuel economy go downhill. There could be a very big difference in your car between 100km/h and 110km/h. Even a stiff headwind in a big, bluff-fronted car like a MU-X can make a difference over the distance you’ve quoted.

If none of those factors are at work, then you really should have the car scanned to see if there’s any problem with the mechanical or fuel systems. Even a dirty air filter can cause a big hike in fuel use, so a once over at the workshop might reveal the answer.

It sounds like you’re on the right track with the transmission, Melissa. Transmission oil goes black when it starts to pick up bits of burnt clutch and band material shed by the gearbox’s internal parts. If that’s happening, there’s also a good chance that the transmission is worn and that’s causing the lack of acceleration and slipping you’re experiencing.

This sort of problem can be caused by low transmission fluid levels, a worn out pump or just plain old wear and tear. A check of the torque converter’s health would also be a good idea, but on the surface, it sounds like the transmission is ready to be rebuilt. Have the vehicle scanned and see what faults – if any – are thrown up by the computer. It could be something simple, but the black transmission fluid tends to tell a different story. It should be a nice, clear red colour.

The Murano is typical of modern Nissans by being a pretty reliable thing by all accounts. The V6 engine, in particular, has a good reputation for trouble-free performance and is widely regarded as a tough unit capable of plenty of kilometres before needing major work.

However, in reality, the Murano has an on-demand all-wheel-drive system, meaning that for the majority of the time, it operates as a front-wheel-drive vehicle. The rear axle only engages when the vehicle detects wheel-slip or the engine is producing enough torque for the rear wheels to join in. That may or may not suit your needs, and it will all depend on what you expect from all-wheel-drive.

The major concerns for some buyers would revolve around the fairly complex driveline used in the Murano. That on-demand all-wheel-drive system used a coupling that engaged the rear axle when the conditions required it. That rear coupling can give problems, beginning with a clunking noise under load. The other concern is more of a general wariness of constantly variable transmissions (CVT) which have been known to have shorter lifespans than conventional gearboxes. That said, the Nissan's isn't a know hot spot for trouble, but it definitely needs to be inspected before money changes hands.

Perhaps the most important thing – as it is with any second-hand car – is the service record. If you can't find solid evidence of the correct preventative maintenance being carried out, the car could easily be a can of worms, regardless of make or model.

Find a new tyre guy. There's clearly something wrong with your car and it needs to be fixed before it's driven any farther. Early Magnas had no provision for altering the rear wheel alignment, but by the time your car rolled off the line, Mitsubishi had changed the design of the rear axle to allow for some wheel alignment adjustment. This is a good place to start.

But really, if you can hear the tyres physically scrubbing while you drive, then you potentially have a bigger problem. And it could be related to a recall that Mitsubishi issued back in 2004. It appears that a bad batch of raw materials meant that the stamped lower control arm on the rear suspension of some Magnas was prone to early failure. The problem became apparent when the arm actually split (at either end) allowing the wheel alignment to become way out of whack. If that's happened to your car, it would explain the symptoms, but also means that it's dangerous to drive at all. At the very least it won't steer properly or predictably and that makes it a danger to other road users.