Car buyers may find that their shiny new purchases have lost most of their value just a few years after they bought them.

Some cars can lose three-quarters of their value after being on the road for three years, according to the Consumers' Association's Which? magazine.

Even cars that hold their value well will probably be worth half their original price after 36 months on the road, the survey suggested.

Best and worst depreciation for 4x4 Off Road* cars

Suzuki Jimmy JLX Estate, lost 63% of value, or �6,290 Honda CR-V 2.0 VTEC SE lost 49% of value or �8,245 Source: Consumers' Association, estimated amount over three years

In general, big cars tend to depreciate faster than smaller cars, with prestige makes like Mercedes and BMW tending to hold their values relatively well, according to the survey of 140 models.

Convertibles and coupes depreciate more slowly than mainstream models, but with the exception of air conditioning, optional extras rarely recoup much of their cost at resale.

The Vauxhall Omega, Suzuki Alto, and Proton Wira were among the worst for holding their value, while the Mercedes Kompressor and Mini Cooper are among the best performers.

Mini value?

In the "supermini" range, according to Which?, a Suzuki Alto 1.0 GL lost 72% of its value after three years.

Best and worst depreciation for 'Large' cars*

Daewoo Leganza 2.0 CDX-E, lost 76% of value or �11,395 Lexus IS200 2.0 SE, lost 47% of value, own �9,510 Source: Consumers' Association, estimated amount over three years

However, a Mini Cooper 1.6 16v, also classed as a supermini, lost only 49% of its value in comparison.

After three years, researchers expected an owner would have seen their car's value decrease by �5,680.

Among models classed as "medium" by the Consumers' Association, which includes popular mid-range cars, the Proton Wira fared the worse.

The 1.5 Lux model lost 74% of its value over three years.

Best and worst depreciation for 'Sports' cars*

Mercedes CL500 (A), lost 56% of value or �37,210 Mercedes SLK 230 Kompressor lost 48% of value or �13,560 Source: Consumers' Association, estimated amount over three years

However, the BMW Compact, was the best at retaining its value among the cars surveyed in this range. The 1.8 model would lose only 47% of its value.

The on-the-road cost of purchasing this car, would be �16,265, however, the owner would still have lost �7,465 over the next few years, the research said.

Luxury models

A Lexus GS300 3.0 (A) and Mercedes S-class 280 (A) were joint best at retaining their value in the "luxury" class, but they would still lose 50% of their value over three years.

However, they were literally a class above a 2.6 V6 Elite Vauxhall Omega, originally costing �24,695. Experts predicted this model would lose 75% of its value over the next 36 months.

In the trendy "sports" car range, the Mercedes CL 500 (A) lost a whopping �37,210 over three years or 56% of its value.

However, another Mercedes, the SLK 230 Kompressor lost only 48% of value or �13,560.