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The bigger question is why you didn't just turn around and drive straight back to the dealership. A brand-new car like this should not have any of these problems, and it's a sad comment on the attention to detail (or lack of it) demonstrated by the dealership that pre-delivered the vehicle when all these things should have been checked. Let's not forget, this is what the dealer delivery charge is supposed to sort out.

The steering wobble is possibly a wheel with a missing balancing weight, particularly as it only appears at a particular road speed. But the steering wheel button issue could be a fault with the wheel itself, the on-board body computer that controls all this stuff or even the software that drives it.

Straight back to the dealer and don't take "they all do that" for an answer.

The recommended engine oil for your car is actually a 5W30 fully-synthetic. That goes for either the petrol or diesel-engined version of the Q5.

It's true that new engines can be 'tight' and this can lead to higher fuel consumption than they achieve with a few more miles on board. And since you're almost at the 30,000km mark now, why not try the dealer's advice and see if things start to improve.

The MU-X was never the most fuel efficient vehicle in its class, but even so, 12.2 litres per 100km on the highway sounds a little excessive (although not as much as you might think). I'd expect this vehicle to return highway fuel economy figures closer to 10 litres per 100km or maybe a bit less.

However, there are several factors that might be skewing your results. The bluff aerodynamics of a vehicle like the MU-X mean that even a slight headwind can increase consumption. So can the addition of accessories such as a bull-bar and roof racks. A set of roof racks on their own can add a litre of fuel to every 100km travelled, and that's if they're not loaded. Throw a spare tyre and some gear up there and it's even worse.

Bigger (taller) tyres can also increase fuel consumption, and so can running your tyres at too low a pressure.

All versions of the Ford Territory form this era used the inline six-cylinder 'Barra' engine from the Ford Falcon. This engine used a timing chain rather than a toothed rubber belt. The chain should be good for the life of the engine and should not need replacing.

That particular variant of the Grand Cherokee weighs an impressive 2336kg. That said, manufacturers often underquote their vehicles' kerb mass, and that could be the case here, so take it as a ball-park figure only.

If you're concerned with overloading the vehicle, the best thing to do is load it as you would and then take it to a local weighbridge to gain an accurate idea of what it weighs in-service. Many council recycling facilities (we used to call them the tip) now have weighbridges.

We have heard some reports of Ranger and BT-50 (they're the same vehicle mechanically) suffering oil pump failures with fairly terminal results for the rest of the engine. The other quirk with this engine is that you can't drain the engine of oil and leave it for any more than a few minutes without the pump running dry and needing to be primed before the engine is started.

Not all mechanics know this and many a Ranger or BT-50 engine has been destroyed when the oil has been dropped from the sump and the mechanic has gone to make a cup of tea or do some paperwork. They return half an hour later, replace the sump plug, fill the engine with oil and start it up. But because the pump hasn't primed, there's effectively no oil pressure and the engine is reduced to scrap in a few short seconds.

The problem is partly to do with the different design of the pump and there are even companies that have engineered more conventional oil pumps to replace the standard units on these engines.

The first thing to do is find out where the leak is exactly. It could be in some of the plumbing that takes the water form the reservoir to the washer jets, but it's probably more likely to be a crack in the plastic reservoir itself.

If that's the case, you could try to mend it with some epoxy (or a lump of some other repair material) but if the tank is old and brittle enough that it's already cracked, the repair will almost certainly be temporary at best. What you need to do is find a replacement reservoir and fit that to the car. The problem there is that even a second-hand reservoir from a parts recycler will probably be just as old as the one you're replacing and might fail in the same way in the not too distant future.

You might get lucky and find an online seller with this exact product brand new, although you might have to order it from overseas. When it arrives you'll probably have to remove the pump unit from your old bottle and fit it to the new one, although some sellers provide the whole battle and pump assembly. That will be the dearer option.

You could also buy what's called a universal washer bottle kit. These are designed to 'fit all cars' but don't actually fit anything perfectly, particularly something relative modern like a Crossfire which has a pretty convoluted bottle shape to fit the space it's designed for.

This needs to be sorted out quickly as a car that you can't be sure is in Park is always a potential to roll away on its own causing who knows what grief and damage. It sounds like there's something amiss with the way the gear selector is talking to the actual transmission, and any resistance in the action of the shifter really shouldn't be there. That said, you do need to have your foot on the brake to select a gear from Park, so maybe you're taking your foot off the brake pedal prematurely.

You're possibly correct that the two issues are related as a car that thinks it's not in Park, will probably not want to allow you to use the walk-away locking mode. But here's the good news: This is absolutely a warranty issue and Isuzu needs to fix it at its cost.

Book the car in to be inspected as soon as possible and, in the meantime, make sure it's parked somewhere from which it can't roll away. Physically chocking a wheel (with a house-brick, a rock or whatever) isn't a bad idea till it's fixed, either.

This particular error code denotes a lean running condition. That is, the engine either has too little fuel or too much air entering it. It's actually quite common on this engine and can be traced to several possible causes. Some of those include bad fuel injectors, a worn fuel pump, an intake vacuum leak, or – and this is where we'd look first on this engine – a bad PCV valve.

This valve is responsible for controlling the crankcase ventilation, but if it fails, it can allow the lean mixture condition to emerge which is when you'll get the error code and a check-engine light. The good news, is there's a quick and easy check if you know your way around an engine.

First, remove the plastic engine cover to reveal the rocker cover and the PCV valve. With the engine running, place a small piece of paper over the hole in the PCV valve. If the paper is drawn to the valve, you have a leaking PCV valve probably due to a broken diaphragm which is allowing extra air to enter the engine and create the lean mixture. If that doesn't work, make sure the oil cap is fitted tightly as a loose cap can cause the same problem. This certainly isn't the case for all engines, but experience has shown that in your car, it's a good place to start.

If the PCV valve theory doesn't work out, you're back to looking at things like fuel pressure, injector condition, intake tract leaks, a bad mass airflow meter or even a powertrain module fault.

The knocking noise could be anything from a poorly secured spare tyre to the struts that hold the boot or hatch in the raised position.

Automatic cars, by law, must have what's called a starter interlock which prevents them from being started in any gear other than Neutral or Park. This is a safety measure to ensure the car can't be started in gear and take off without the driver being in full control.

Which means your problem sounds like a coincidence rather than the result of trying to start in Reverse. What you can try is to start the engine in both Park and Neutral, rather than just Park. If it won't start in either of those positions, you may have either a problem with the starter system or the small switch that controls the interlock function.

But it's hard to imagine that tyring to start in Reverse would have damaged this interlock mechanism. Again, it sounds awfully like a coincidence. If it is the interlock system, you could try to remove the centre console to gain access to the gearshift mechanism and maybe spray some contact-cleaner onto the interlock switch, cycle it a few times and see if that restores power to the starter.