Q We own a pair of ageing cars with high mileages — a 1999 Jeep Cherokee and a 2000 Renault Mégane. We would like to swap the Renault for a small car capable of handling both daily commuting and rough-terrain use, but we’re not sure what to do about the Jeep. My wife is expecting our fourth child and we would like a seven-seater for the school run, but we also need a car to pull a horse trailer. Should we keep the Jeep for the trailer and then buy a big car for school runs? Or should we trade it in and get a pricier 4x4 that can do everything? — RA from Pateley Bridge, North Yorkshire

A As your Jeep will have depreciated by a great amount, you may as well keep it for horsebox-towing duties and buy a used seven-seater MPV exclusively for the family driving.

The Citroën C8 is a good-value option and a 2.0HDi 16V SX from 2005 would cost about £9,000. The Mazda5, which has sliding rear doors, is another sound family choice, and the 2.0D TS version, registered in 2006, could be yours for about £8,000.

With the horsebox and the school run taken care of, you’re left with a wide choice of small, three-door cars for commuting purposes. Try the Fiat Grande Punto, Toyota Yaris, Honda Jazz and Vauxhall Corsa, to see which handles your terrain the best. If none of them proves to be suitable for you, then consider the Fiat Panda 1.2 4x4. A 2005 model would cost you in the region of £4,500.

Q When I bought my W-reg Rover 75, it came without the radio’s anti-theft security code. I am very concerned that without this code, I would be left without a functioning radio if the car’s battery were to be disconnected. I have the radio’s serial number, but my ex-Rover dealer cannot help and says that XPart — the company that now supplies Rover parts — won’t be able to help either. What do you suggest? — BD from Wickham, Hampshire

A All XPart dealers should be able to obtain this code for you. Ask your ex-Rover car dealership to e-mail the head office, which will be able to find the code — typically within a couple of hours. There will be a charge, probably of £20 or so.

If you still have problems, you can contact XPart direct on 0870 242 4791 (www.xpart.com).

Q I recently bought a windscreen-cleaning product called W5 Car Care Nano-Solution. I was led to believe this would help to repel dirt once the car’s windscreen had been treated with it, but it hasn’t worked like that. To make matters worse, I now have a permanently greasy windscreen, and each time the wiper blades traverse the windscreen, they leave a mist of fine droplets behind them, that temporarily obscures my view. How can I now remove this product? — SO from Hayle, Cornwall

AUse a weak solution of washing-up liquid, but ensure that you rinse it off thoroughly and don’t wash the bodywork with the same fluid, as it will remove any protective wax coating. You will then almost certainly need to replace the wiper blades, as these will probably have become coated with the product.

One of the best products for the application you describe is the award-winning Rain-X Rain Repellent. It is sold in 200ml packs and costs about £10, including delivery, from www.theultimatefinish.co.uk

QWe have a one-year-old Citroën C4 Picasso that is driving my wife and I mad. When the engine is turned off for more than a couple of minutes, the car enters “economy mode” and all the electrical accessories cease to operate, including the radio and windows. This is frustrating if we are, say, waiting to board a ferry. The dealer says there is no way to change this, but is he right about this? — BR, via e-mail

A Automated systems such as this one are fitted to ever more vehicles (not just Citroëns) and cannot be turned off. The reason given by manufacturers is that modern cars have such complex electronics that if they were all left “live”, the car’s battery would quickly flatten.

Some cars give you more discretion than Citroëns do in terms of how long the electronics will work while it is stationary. Audi and BMW switch off most electrics almost simultaneously with the ignition but the windows can be operated for a minute or two, and the radio will continue to work after that. On Fords, the radio lasts for an hour after the ignition is switched off.

Even so, the real problem is that few modern cars have an indicator light to warn you when the battery is about to go flat.

QI recently put my Golf GTI in for its three-year service with a VW main dealer. The car has only 23,000 miles on the clock. I was charged £55 for 4.6 litres of new oil so when I checked the dipstick I expected it to be a clear honey colour but it was still black. How can I tell if the oil is new? — AF, from Bolton

AThe only time oil looks light and golden is when the engine has never been run. It’s often thought that when the oil is changed during a service every drop is drained, but some always remains in the smaller parts of the engine. These tiny amounts of old oil and the carbon deposits in an engine will slightly dilute the new oil, like putting a used paintbrush into a glass of water. The only way to be sure the oil has been changed is to watch it being done.

QI have a problem with large numbers of flies hitting the paintwork of my new VW Golf, particularly on sunny days. Repeated washing makes no difference. The carcasses leave body fluids behind, which are difficult to remove. Any suggestions? — TI from Exmouth, Devon

AIt’s a fair bet that your car is a light colour. Yellow is a natural stimulus to plant-feeding insects, which associate it with food. Lighter cars (especially white ones) also tend to attract insects that need a bright landmark in order to swarm.

Try not to leave the marks on the car for any length of time of time or they will bake themselves onto the paintwork. Do not wipe them off dry, either, or you could put tiny scratches into the paint surface. Instead, spray the affected areas with a product such as Turtlewax Bug and Tar Remover (£4.99 for 500ml from Halfords). Once it has thoroughly soaked in, you can wipe the debris off safely.

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