Q In January the oil-warning light came on in my VW Eos. My dealer said rodents had been chewing through wires and it cost £120 to repair. It has just happened again and this time it cost £900 to fix as the animal or animals had chewed wires underneath the dashboard and had started on the steering cables. What can I do to stop it happening? – OM from Dorking, Surrey

A This problem has almost certainly been caused by mice attracted by the car’s cosy underbonnet area. They’re inveterate nibblers and will try almost anything, edible or otherwise, and it doesn’t take long before serious damage is done.

You could try using mouse/rat poison. Don’t put it in the engine bay as it may give off fumes and, in any case, you need to stop them before they get that far. Put out the poison in small piles on discarded food lids. Use several lids as mice seldom eat from the same place for long.

A better solution, especially if you are worried about children or pets (yours or your neighbours’) is to opt for mouse-bait stations: small, lockable, sealed plastic boxes such as the Tomcat, which typically costs £16.50 for five. These can be bought, with poisoned bait, from a hardware store, from a farmers’ merchant or online (try www.ppcsupplies.co.uk, 01386 552 545).

Place them on the floor under the centre line of the vehicle, so you don’t drive over them. Don’t dawdle: it’s quite possible that your intruder vermin could get into the car’s cabin and build nests, or even breed in the sound-damping behind the trim.

Q I have driven Vauxhall Astras for many years but now want something more economical. Good headroom and legroom are important, although I would consider a smaller car. I am looking for a five-door hatchback, automatic, about two years old and have a budget of £10,000. Any suggestions? – LB from Hitchin, Hertfordshire

A Try the Daihatsu Materia. It has a 1.5 litre engine and can be bought with manual or auto transmission. Its boxy design provides good headroom and all models come with air-conditioning and rear-parking sensors. A 2007 07-registered car costs about £10,000. Last week, the Daihatsu website (www.daihatsu.co.uk) revealed that an almost new Materia with only a few dozen miles on the clock at Woodford Motor Company (0208 504 0017) was available for £9,995.

You should also consider the Renault Modus. It looks like a shortened Renault Scénic with a high roofline and good legroom but with shorter overhangs. A new 1.6 Dynamique model costs £12,720, so you should be able to get a 2007-registered car for about £9,000.

Q I have a 2005 Ford Focus 1.6 Zetec. This came with two keys (one remote and one nonremote) but as neither is foldable, I keep stabbing myself whenever I put one in my pocket. I spoke to my Ford garage in the hope of getting a folding key and was told these are not listed for my Zetec. Is there an option to obtain a “folding” key? – TR from Christchurch, Dorset

A This seems a strange answer from your dealer because folding keys are readily available for your Focus. The price of the remote-control key and the cutting is about £100, plus £70 for programming the new key to the car’s electronics.

Q The soft top on my wife’s two-year-old Mazda MX-5 has marks on it caused by careless use of a power hose. These marks look like squiggly lines in the fabric.

How can I remove them? I tried Autoglym’s Fabric Hood Cleaner and the Fabric Hood Protector but they made things worse by leaving stains where the protector has dried. – BW from Northern Ireland

A This sort of damage isn’t repairable, unfortunately, and it means you’re looking at buying a replacement hood. Pressure hoses should be used with great care on all parts of cars. Even using a standard garden hose on a fabric hood must be done using a gentle spray pattern.

A roof supplied by Mazda will cost upwards of £680, plus about six hours’ fitting time. As an alternative, the Car Hood Warehouse (www.carhood.com, 020 8391 5326) can supply a vinyl roof for £323, plus about £40 carriage. If you’re a bit handy, fitting it yourself is possible. If not, the firm has an installer in Belfast who would probably charge £250.

This should all be covered by fully comprehensive insurance, but you will have to pay the excess and possibly lose your no-claims discount.

Q While tidying my garage the other day, I found a five-litre plastic jerrycan full of unleaded petrol. It was still tightly sealed but has probably been there for three or four years. Will it have gone off or is it still safe to use in my car? – AB from Devizes, Wiltshire

A Petrol does go off to some extent. If left long enough and open to the air, it is going to be less willing to fire up in the cylinders. It would be a bit like using a lower octane fuel. Fortunately, your can has been sealed properly. Even if that were not the case, mixing the older fuel with an almost full tank of new fuel should be okay.

You need to be careful when you open the can. Petrol vapour will build up inside, especially during hot spells.

When the can is opened, there will be a sudden rush as the highly flammable vapour is expelled so don’t open the can near anything that could ignite it.

Q I am expecting my third child in November. I will then have three children under the age of four, all requiring a child seat. Do you know of any small MPV or family car that can accommodate three child seats in the back and is also exempt from the London congestion charge? – AN from Henley, Oxfordshire

A You don’t have to buy an MPV or seven-seater just yet because most family saloons or estates will take three child seats in the rear, although they probably won’t have Isofix fittings across all three rear seats like many MPVs.

Go for a car with three-point safety belts on the back seat and get child seats designed to fit them. If you are buying an older vehicle with only a two-point lap belt in the centre, it is still possible to install an approved child seat. Both the Britax Eclipse Si (£95) and the Fisher Price Safe Voyage (£65) from Stork Talk (www.storktalkmidlands.co.uk, 0115 930 6700) have been crash-tested to legal standards using only a centre lap belt.

Hybrid petrol-electric vehicles such as the Toyota Prius and Honda Civic are exempt from the congestion charge, as are some cars that run on LPG (liquefied petroleum gas). You could consider having a car converted to LPG by an approved installer, for £1,500-£2,000. The Energy Saving Trust (www.energysavingtrust.org.uk, 020 7222 0101) has a register of companies that can carry out the work to the required standard.

Ken Livingstone, the former mayor of London, was planning to extend the exemption to petrol/diesel cars that emit less than 120g/km of carbon dioxide (band A or B for road tax). However, Boris Johnson, his successor, has said he will scrap the plan to link the charge to carbon dioxide emissions. He is also reviewing the western extension of the charging zone, which took effect last year.

Q I have about £2,000 to spend on a secondhand car. I commute mainly on motorways, but also in stop-start London traffic. I am looking for a car that is sturdy, safe and reliable for motorway travel but is still not too large and unwieldy to parallel park on my busy residential street. The less fuel it guzzles, the better, and the more reliable, the better. I don’t want a 4x4 or MPV and I don’t want diesel. Any ideas? – EW from Ely, Cambridgeshire

ALook for a car with a good service history and be prepared to buy one in an unfashionable colour, as this often gets you more for your money. Private adverts and auctions give you the best potential for a bargain.

It could also be worth talking to a franchised dealer. Dealers take cars worth £2,000 in part exchange but don’t usually sell them on the forecourt, preferring to pass them on to an auction house. If you put a word in, a dealer might be willing to save himself some hassle by selling a part-exchange car straight to you on a “trade sale” basis, without warranty, provided you act quickly and decisively.

We’d suggest you go for something Japanese, such as a Honda Civic, which has a good reputation for reliability. Your budget gets a 1999 T 1.5 LS. The old-style Civic drives well and is compact and economical.

Also look at a Mazda 323 of a similar age or consider a Nissan Almera. It is not a hugely fashionable car but it is underrated. Your budget gets a 1999-2000registered 1.6 GX, which came with factory-fitted air-conditioning.

All three cars fit into the family hatchback category and combine compact dimensions with ride comfort.

Please e-mail your questions for our experts to carclinic@sunday-times.co.uk. Alternatively, write in to Car Clinic, InGear, The Sunday Times, 1 Pennington Street, London E98 1ST. Please supply us with a daytime telephone number, the town you live in and as much detail about your car as you can. We regret we cannot send personal replies or deal with every letter, so please do not send original documents or SAEs. Advice is offered without legal responsibility.