Toyota Problems

You are in a tricky situation, the oil you use is a good quality brand and shouldn't cause any problem, but I would follow the dealer's advice and switch to a 10w-30 grade oil. I'm sure you'll find Valvoline make one, so you can stick to the brand you like and trust.

It’s not normal to get black smoke under acceleration, that suggest it’s being over-fuelled and should be looked into. Aftermarket chips can be worthwhile, but they generally take the engine closer to the limit than does the factory chip, so you need to find an installer who can be trusted to do the job well. I wouldn’t do it on your car until the warranty runs out, and then consider it.

You’re buying a high mileage car so be careful to check the condition of the engine and driveline and walk away if there’s any suspicion they’re close to worn out. There’s little difference between the Landcruiser and the Patrol, but avoid the 3.0-litre turbo diesel Patrol as it has engine issues.

You don't have any comeback on Toyota to provide with a fifth alloy wheel, the Aurion is supplied with a steel wheel as a spare, as many cars are. It's a full-sized spare wheel with a full-sized tyre so there's no problem running it for as long as you need.

The dealer is incompetent, and lazy. Contact Toyota’s customer assistance people and report your experience, with the car, and with the dealer, as they need to be hauled over the coals. There is something wrong with your car and, you’re right, it needs to be fixed. If the dealer and Toyota say it can’t be fixed, which I seriously doubt they will, park it on the dealer’s forecourt and ask for your money back.

Check the wheel bearings, and also the drive shaft joints for wear.

Yes, it can be converted, and converted successfully, but you really need to use an injection system, either vapour or liquid because the risk of damage to the plastic intake manifold in the event of a backfire. That risk is high with an old venturi/mixer type system, but virtually nil with a modern injection system.

There’s no problem about buying a generic brand of coolant off the shelf and filling the system, just make you mix it to the correct ratio. It is a good idea to replace coolant at times and it might well be worth doing that at this time of your wife’s car. Before doing anything, however, inspect the cooling system for leaks that might have caused your wife’s car to lose coolant.

While most automatic transmissions today are sealed for life and carmakers say they don’t need any servicing it pays to be cautious, especially when towing as you do. The guys at AW Automatics say it holds 8-9 litres, the service fill is three litres, and you should use Toyota WS trans fluid if its in warranty, and Valvoline Synthetic Trans Fluid if its out of warranty.

The light coming on suggests that it is about to stall, so it’s unstable at low speeds. Without having a diagnostic lead to go on you’re best to cover the basics, and replace the plug leads, perhaps the coils, check the PCV valve, and clean the throttle body.