According to Glass’s, classic car owners who keep the mileage down to minimise depreciation risk losing more money than they might potentially save. "Condition remains the primary defining factor in determining the worth of many popular classic cars, not mileage, and deterioration in condition resulting from lack of use can often be costly," explains John Glynn, Editor of Glass’s Older Car Guide.

"When in excellent condition, many if not most of today’s true classics are appreciating assets. Assuming that their excellent condition is kept up, the value of the best examples with average mileage should continue to rise year-on-year, even if only gently. Though some owners might feel that they are increasing the value of their classic by using it less and keeping the mileage down, it’s worth remembering that any rises in value as a result of lower mileage are likely to be modest and must be offset against the lack of reward in not using and enjoying the car."

As regular use starts to dry up, so too do bearings, bushes and other mechanical parts. Brake calipers, handbrake mechanisms and clutches begin to seize. Oil drains back from extremities, causing increased wear. Condensation can collect in other fluids, damaging seals and rusting wheel cylinders and so on. 

The overall effect of this lack of use is a negative effect on mechanical condition and worth, and increased costs in keeping the car up to scratch.  "Based on current evidence, any future monetary rewards for keeping mileage down are unlikely to compensate owners for the lack of driving pleasure. The message to enthusiasts is clear: get out more!" says Glynn.

Exceptions that prove the rule

According to Glass’s, exceptions to the general rule outlined above are those cars in the £15,000-£30,000 price range, where lower mileage increasingly offers an appreciable advantage. "As this is the bracket where serious car collectors really start to make their presence felt, this is perhaps unsurprising," adds Glynn.

Very low mileage examples of the best cars in this bracket – such as some early and rare Porsche 911’s, certain Mercedes convertibles and the Aston Martin DB6 – could be up to forty percent higher in value than a higher-mileage but good condition car. "The relative rarity of low mileage examples of these classic ‘drivers’ cars’ means that the gap between these cars and their higher-mileage siblings will continue to increase, therefore justifying the mileage preservation habit slightly more in their case," adds Glynn.