This is probably a simple case of an automatic transmission doing what it’s designed to do. In order to keep the engine in its comfort zone (and making sufficient power and torque to haul the caravan at the speed you’ve chosen) the transmission will shift through its gears to achieve that happy balance.

Any time you encounter a hill or even a headwind (and it’s more so with a heavier caravan) the transmission will assess what speed you want to hold, and then (via changing gears) keep the engine at a speed that supplies the necessary performance. Even a hot day can cause a change in the shift patterns as the transmission aims to take the strain off the cooling system by giving the engine and easier time. Again, a big, heavy caravan will amplify this effect.

However, if the transmission is changing gears for no apparent reason, then you may need to have the calibration checked and perhaps even reprogrammed. Don’t forget, though, that a modern transmission is a pretty clever piece of gear that can even choose to shift down gears going downhill to take the strain of the vehicle’s brakes. Don’t confuse an active transmission with a dud one. And if you still think the behaviour is odd, then an electronic scan of the vehicle might provide more information.

Okay, here’s the bottom line: All engines use a little bit of oil. If they don’t there’s either something wrong with the oil pump, or the owner is kidding themselves and not checking the oil level correctly. Modern turbo-diesels also 'breathe' a little oil back through the engine as part of the emissions control system, and owners with an aftermarket catch-can system often find a bit of oil winds up in there instead of being burnt in the engine.

The question is how much is too much. I don’t think 700ml per 2000km is excessive and your dealer’s views will be based on the official figure from Isuzu. But in the real world, owners are reporting oil consumption of around a litre to 1.5 litres per 5000km. At which point, your engine is right on the money.

How you drive the vehicle and whether you tow a heavy load will also affect oil consumption, as will ambient temperature and the type of oil you use. It’s a fact that modern, lower-friction engines are designed to use a little oil in the name of saving fuel, and it’s something car owners need to get their head around. Keep an eye on that dipstick and you should be fine. Checking the oil on a regular basis will also tell you whether the engine’s drinking habits have changed; a much more valuable piece of knowledge to have.

This is an annoying but relatively common problem in many cars, not just the Isuzu. Because a car’s air-conditioning system dehumidifies the air (as well as cooling it) the water that was suspended in the air has to go somewhere. When everything’s working properly, there’s a small drain-hose from the air-con unit, through the floor to under the car where the water can be dumped with no problems.

But what often happens is that the little tube or drain-hose becomes blocked. At which point, the air from the atmosphere has nowhere to go other than inside the cabin where it causes the mayhem you’re experiencing. By locating the drain-tube and cleaning it out, the problem should go away. If not, you need to look more closely at the car’s heater matrix which also lives under the dashboard and can leak coolant into the cabin for a similar range of problems.