A major survey of more than 100,000 used cars aims to quash fears that the market is being flooded with diesels.

Some market commentators claim diesel residual values will be affected by an influx of used cars caused by company vehicle drivers choosing such vehicles for tax reasons.

Since the introduction of carbon dioxide-based company car tax, sales of diesel vehicles have rocketed, as they have low CO2 emissions, which means low tax bills for drivers.

Compiled by auction giant Manheim Auctions, the Market Analysis report studies variances in end-of-contract mileages and prices achieved between petrol and diesel variants of the same model.

The report found that across the board there has been some stability in the replacement cycles and mileages of key fleet models.

It adds that total volumes in diesels have grown marginally with the proportion of petrol and diesel variants averaging about 71% and 20% respectively throughout the year.

It states: "This has reinforced the view that there hasn’t been the huge influx of diesel cars hitting the market, as some commentators have claimed."

The Manheim report shows diesel cars have on average covered about 34% more miles than the petrol models in the survey.

It found the average annual mileage on the petrol models was 14,309 compared to 19,098 miles on the diesel.

In terms of CAP Clean, diesel comes out on top in the executive and 4x4 sectors gaining premium of up to 4%.

On typical fleet models, the survey says: "Most of the mainstream ‘working-fleet’ models show favourable performance for diesel but with a much narrower gap of generally about 1% or under.

"The few exceptions to this rule include the Ford Focus range where petrol has outperformed diesel over the previous 12 months by an average of 1.8% against CAP Clean."

Manheim Auctions group director of planning and marketing Rob Barr says: "The reports are based purely on transactions so the findings are pretty indisputable and obviously represent very valuable data. Our intention is to continue to focus on key fleet issues and select sections of the quarterly Market Analysis report for further in-depth review, as the market requires."

Diesel versus petrol

Model Fuel/percentage split Average mileage month/year Performance vs CAP*
Petrol Diesel Petrol Diesel
Ford Focus 80% 20% 1,274/15,291 1,675/20,106 Petrol outperforms diesel +1.8%
Renault Megane Scenic 78% 22% 1,048/12,577 1,517/18,205 Petrol outperforms diesel +0.9%
Volkswagen Golf 68% 32% 1,002/12,020 1,504/18,047 Diesel outperforms petrol +0.2%
Vauxhall Vectra 79% 21% 1,271/15,253 1,620/19,444 Diesel outperforms petrol +0.8%
Ford Mondeo 80% 20% 1,231/14,774 1,601/19,208 Diesel outperforms petrol 0.5%
BMW 3-series 89% 11% 1,194/14,332 1,823/21,880 Diesel outperforms petrol 1.6%
Land Rover Freelander 65% 35% 1,071/12,848 1,447/17,365 Diesel outperforms petrol +2.9%