Used car values are becoming more volatile as the market becomes more complex, Cap HPI has warned.
The automotive data specialists have reported a market realignment through the first half of the year with values heading downward following an unusually strong year in 2018.
The declines slowed in August as the market stabilised with a fall of 1.0%, the smallest fall since March.
So far this year, Cap HPI has seen a drop in used values greater than the same month in the previous three years.
It said its Live values data points to a more stable period ahead as demand and values are more closely aligned.
Average diesel car values are consistently dropping by more than their petrol counterparts, with August seeing a 1.1% fall compared to 0.8%.
Derren Martin, head of UK valuations at Cap HPI, said: "The data shows the used car market is becoming more complex and volatile.
“Used vehicles reach the wholesale market through a multitude of routes that all impact on values.
“We also see the pace of the market accelerating as vehicles from the fleet and retail sectors are remarketed faster than ever.
"With the increasing number of models, powertrains, options, and acceleration in generations, it's clear that the used market will only become more complex as time progresses.
“And while we don't expect any major shifts in the overall market, we are seeing an increasing disparity and volatility between makes, models and powertrains as consumer tastes shift.”