Values for used diesels grew by 5.95% in February, according to Cox Automotive.
The owners of auction business Manheim recorded a third consecutive annual rise in average prices, with vehicles passing through its online and physical lanes achieving an average of £7,158, an increase of nearly 12% year-on-year.
Diesel performed strongly in the wholesale market, with values at auction increasing by 5.95% in February (£9,046 in 2018 vs. £8,538 in 2017), and vehicles in the 10k to 20k mileage band achieving the strongest average growth in value at 4.41%.
Manheim figures also show significant growth in demand for petrol vehicles, which experienced double-digit growth of 20.05% year-on-year to £5,126. (£4,270 in 2017).
Philip Nothard, head of external communications at Cox Automotive, said: "Our data shows that the only category where petrol values didn't grow was the £10k to £20k mileage band, which is where we've seen diesel excel. Petrol vehicles in this band dipped 1.38% to £13,415 in 2018, which is down from £13,603 in 2017."
Overall volumes were down (6.71%), with an exception in the 10k to 20k mileage band at 3,517 (up 2.39% on 2017 at 3,601).
Nothard said: "We believe the dip in overall volume is down to a number of factors. Scrappage schemes, a decline in new car registrations, the trend towards consolidation creating larger retailers and the general shift among dealers to focus on used car stock are all having an impact.
"This is driving a strong wholesale market, with demand for used stock outstripping supply. The quality of stock coming through the auctions is however of consistently high quality and Manheim is seeing extremely busy sales with dealers chasing the ready-to-retail vehicles to drive stock turn and reduce days in stock - it's all about helping dealers to sell cars faster when consumer demand is peaking."