Q Given the high price of fuel in the UK, I have been thinking about hiring a fuel bowser (a container for transporting liquid fuel) to bring a supply of diesel back from, say, Luxembourg, where it is considerably cheaper. Is a private motorist allowed to bring back fuel across the Channel for his own use? Are there any restrictions on it, as there are for quantities of wine and cigarettes, for example?

LL from Hertfordshire

A In principle this sounds reasonable enough, given that the saving you could make on the cost of the fuel would be enough to offset the hire of a bowser (about £160 a week), the extra fuel you’d use towing it and the undoubted premium your insurer would require for the extra risk (assuming you’d be allowed through the Channel tunnel or on the ferry).

However, HM Revenue & Customs has already thought this through and, unlike for wine and cigarettes, there is no petrol or diesel allowance other than what is in the vehicle’s fuel tank. Any fuel other than this would be liable to Vat and duty. That technically would include even a jerry can in the boot, although it seems likely that only the very harshest of customs officials would bother processing such a small amount.

Q I recently bought a Mazda6 MPS with four-wheel drive and am keen to learn how to get the best out of my car. Are there any good books on handling such vehicles?

BH from Hampshire

A While a book might offer general advice, a better option is to gain some hands-on practical experience. The safest place to do this is on a test track, with an instructor who is experienced with four-wheel-drive saloons.

There are courses all over the country but the Thruxton Motorsport Centre in Andover (www.thruxtonracing.co.uk , 01264 882 222) is closest to you and can offer you an hour’s tuition in your Mazda on its track for £150. Prodrive (www.prodrive.com , 01676 536 117) offers a two-hour course in a four-wheel-drive Subaru Impreza for £125.

Q According to my Glass’s Guide, my 2005 4.2 litre supercharged Range Rover Sport with 36,000 miles on the clock, should trade at £30,000. But when I called a dealer, I was offered just £20,000. I understand about profit margins but isn’t that excessive?

IP from London

A According to the July edition of CAP, the trade’s guide to used car valuations, your Range Rover has a “trade valuation” (what you would get in part exchange at a dealer or by selling for cash at an auction) of £25,050, assuming it is a 2005 05 model, or £26,050 if it is a 2005 55 plate. The dealer offer of £20,000 would therefore on the face of it seem low.

However, the market for 4x4s - particularly high-performance models - has shrunk in recent months, partly due to the rising cost of fuel and the tendency of such vehicles to need a lot of it . The Range Rover Sport has dropped some £2,800 in value since May, according to CAP. So, although it seems harsh, we suspect £20,000 is now closer to the real value that these cars are fetching on the open market.

A few calls to Range Rover franchised dealers and a couple of nonfranchise specialists is likely to confirm the bad news. The only good news is that prices could well be about to bottom out as the cars start to look very good value.

Q I’ve noticed several new car dealers promoting a product called Supagard. I’m told the vehicle is given a special coating at the point of purchase that supposedly keeps it in “showroom condition” without the need for regular waxing. The seat fabrics are also coated to ensure spillages can be easily wiped off. This sounds great but, as it costs £300 is it worth it?

NDP from west London

A Supagard is one of several “paint protection” products offered by franchised-vehicle dealers. Others include LifeShine, made by Autoglym, and Diamondbrite.

In essence, what you are paying for is a professional polish, using top quality, long-lasting products, which will leave a coating over the bodywork to offset attack from airborne pollutants such as acid rain, diesel film and even tree sap. You will get a warranty of 3-10 years – but in most cases, you have to apply a top-up polish/cream every six months yourself. Opinions of those who have tried these products vary.

None of these treatments will stop stone-chip damage. But the Armourfend system (www.armourfend.co.uk, 01992 892 896) is designed to do just that. It’s essentially a series of thin pieces of transparent film that are tough to penetrate yet are virtually invisible. A mid-range saloon such as a BMW 3-series, would cost £640 for complete coverage.

As for upholstery protection, applying Scotchgard yourself does a similar job at £4.99 for 400ml (tinyurl.com/6fyn67, 0870 850 2194).

Q I am a 65-year-old woman and drive a five-year-old BMW M3 coupé, which I have had since new. I love the car but am now ready for a new one and think it may not be prudent, in view of my advancing age (although I am very fit), to buy another M3. I do most of my driving out of town in the west of Scotland. Do you have any suggestions for a replacement that will still give me some of the joy of my current car?

EAM from Glasgow

A The BMW M3 is such a great car and, if you are as fit as you say you are, it might not be time to switch to something more sedate just yet.

If you are still set on a change, there are other cars that are fun to drive but a tad more modest in terms of performance. We’d suggest you try the Audi A5 coupé. It has a generous cabin with good access and looks gorgeous. Prices start at around £28,000 for a 1.8 TFSI with an automatic gearbox but our pick of the bunch would be a 3.2 FSI with an auto box, and a 0-62mph time of 6.6sec. It would also be cheaper than a new M3 coupé (£51,330) at about £34,000.

Also consider the new Mercedes-Benz CLC. It is compact, well built and comes with a huge range of engines. Quickest of the range is the 350 petrol, which comes with auto transmission as standard. A CLC 350 Sport costs £27,240 and can be personalised with the sort of options you have grown used to in your BMW. It also does 0-62mph in 6.3sec.

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