A 13ft trampoline, vacuum cleaners and a stag's skull complete with antlers are just some of the items found to be kept in cars.
A survey by the Department for Transport has revealed that as many motorists use their cars as a storage option they had better be sure their car insurance covers content.
One woman from the north west built up a considerable amount of clutter in her car over two years, with items including a kettle, a sandwichmaker and two vacuum cleaners.
The survey also shows that 10% of those polled could not remember the last time they cleared the clutter from their car.
Tim Anderson, of the Energy Saving Trust, said: "We can all lighten our load to avoid emitting unnecessary carbon dioxide into the atmosphere. A quick spring clean of your car boot will make your car lighter, meaning you need less fuel, saving you money and CO2 emissions."
Transport minister Lord Adonis said: "If all motorists adopted smarter driving techniques it would save around 5.5 million tonnes of CO2 every year - collectively, that's a fuel cost saving of over £2 billion a year for the motorist."
© Press Association 2008