2020 Isuzu FVM Pricing and Specs

Not being able to match a vehicle’s official fuel consumption number is not just common, it’s something just about every owner discovers the hard way. That’s because the test that determines the number is a laboratory test, not a real world one. The test figure serves as a comparison between different makes and models, not a realistic expectation of fuel consumption.

However, the additions you’ve made to your car will all increase fuel consumption. A nudge bar and tow bar both add wight and a set of roof bars can easily add a litre of fuel to every 100km travelled thanks to increased aerodynamic drag. Even the GVM upgrade might make a difference, especially if it sits the vehicle up higher, affecting aerodynamics even further. If you’ve also fitted bigger tyres, fuel consumption will rise even more. To be honest, I reckon 10 litres per 100km is about right for this vehicle and matches most other vehicles of this type. Don’t forget, either, that an Isuzu MU-X is a much bigger, heavier vehicle than a Subaru Forester.

A car that’s left to sit for a length of time will often develop a flat battery as things like the clock and security system slowly drain the battery. But this should not happen in just three days.

If there’s absolutely no drain on the battery (as checked by your electrician) then suspicion turns to the battery itself. It may have done this since it was brand-new, but the battery could have a manufacturing flaw or internal damage that means it won’t hold a charge beyond three days. Borrow a different battery and see if the problem goes away.

What you’re experiencing is the transmission calibration that many modern vehicles use to increase fuel economy. By always trying to be in a higher gear, the vehicle will record a better fuel economy number on the official test that compares it with its competitors.

The downside is that the constant upshifting means the vehicle will sometimes find itself in a gear that’s slightly too tall, and that’s when you’ll start to get the symptoms of feeling like the engine is labouring or lugging.

As you’ve noted, when the car shifts down a gear, the sensation goes away. The solution is to manually pull the car back a gear when this happens. If t really bothers you, you could ask Isuzu if there’s a software update that makes the transmission a little less eager to be in top gear.