It's good news. Your car is indeed compatible with E10 fuel which means you can use the slightly cheaper fuel without risking damage to your vehicle. The car should also run exactly the same as it does on normal unleaded petrol, although you may find you use slightly more fuel per 100km. This should, however, be more than offset by the savings you'll make at the pump.

There are many, many things that can make a car overheat. A faulty radiator, collapsed radiator hose, jammed thermostat, blown head gasket, low coolant level, incorrect ignition or camshaft timing, faulty fuel injectors, the list goes on and on. So you need to have the car scanned electronically to see if a fault code is offered up that could be the cause or part of the problem. First, though, I’d have a close look at the obvious stuff like a leaking radiator or blown radiator hose to make sure that it’s not a really simple fix. Even a faulty radiator cap – as simple as that sounds – can lead a car to overheat.

To be honest, a 34-dgree ambient day should never be enough to make a modern car overheat, especially not one like a Holden Commodore which was designed here to easily cope with our weather and temperature extremes.

It’s interesting to note that you bought the car from a dealer, so it would be worth going back and checking the paperwork to see if the car was sold with any warranty. It’s doubtful, however, as a 2005 model car falls outside the boundaries of Victoria’s statutory warranty legislation (generally a used car must be less than 10 years old and have travelled less than 160,000km before a statutory warranty applies from a licensed car dealer). A good mechanic who knows this type of car should be able to sort it, but have it checked soon; continuing to drive it with an overheating problem is a sure way to make small problems bigger ones.

Without hearing the car firsthand it’s impossible to speculate on what might be wrong with your car, but I would suggest that it’s unlikely to be the spark plugs. Your best course of action would be to get a mechanic to check it for you.