Three-Year-Old Cars Lost £195 in August as Diesel Values Keep Falling, Cap HPI Shows

• Solera cap hpi says the average three-year-old car with 60,000 miles lost £195 in value in August, a 0.9 percent fall in used car values across the month against 0.1 percent a year earlier.
• Diesel values at three years old have now fallen for five months in a row, down 1.5 percent in August and a further 0.6 percent so far in September, with diesel at around 195p a litre.
• Older cars are losing the most: 10-year-old cars fell 2.7 percent in August and 2 percent so far in September, while used electric and hybrid values are rising.

If you own a used car, its value fell faster than usual over the summer. Solera cap hpi, the vehicle valuation business, reported on 26 August 2026 that used car values dropped 0.9 percent in August, which took £195 off the average value of a three-year-old, 60,000-mile car heading into September. A year earlier the same measure fell just 0.1 percent.

The latest reading, published on 28 September 2026, shows the slide slowing but not stopping. The average value of a three-year-old used car is down 0.3 percent so far in September, and the pressure is heaviest on diesels and on older, higher-mileage cars.

Diesel Values Have Now Fallen Five Months in a Row

Diesel has been the weakest fuel type at the three-year point for months. In August it fell 1.5 percent for the fourth consecutive month. So far in September it is down a further 0.6 percent, which makes five months of falls in a row.

Chris Plumb, head of current valuations at Solera cap hpi, tied the trend to fuel prices. He said diesel at around 195p a litre is difficult to ignore, especially when it is so much more expensive than petrol, and that dealers are being more selective about the diesel cars they buy.

The pump price gap backs that up. Government weekly road fuel prices for the week to 21 September 2026 put petrol at 172.01p a litre and diesel at 195.53p. On a 55-litre tank, that is £94.61 for petrol and £107.54 for diesel, a gap of £12.93 a fill (our calculation from the published pump prices). Over twelve fills a year the difference comes to £155.

The fuel-type figures for the three-year-old market read as follows:

• Diesel: down 1.5 percent in August and 0.6 percent so far in September.
• Petrol: down 1 percent in August and 0.5 percent so far in September.
• Plug-in hybrids: down 0.9 percent in August and 0.8 percent so far in September.
• Hybrids: down 0.1 percent in August, then up 0.5 percent so far in September.
• Battery electric cars: up 0.1 percent in August and up 0.3 percent so far in September.

So the split is clear. Diesel, petrol and plug-in hybrid values are sliding, while hybrids and pure electric cars are holding or rising.

Older and Cheaper Cars Are Losing the Most

The age of the car changes the size of the fall. In August, one-year-old cars at 10,000 miles fell 0.5 percent on average, five-year-old cars at 80,000 miles fell 1.6 percent, and 10-year-old cars at 100,000 miles fell 2.7 percent. Cars worth less than £5,000 recorded an average fall of 3.4 percent.

September is following the same order. One-year-old cars are down 0.2 percent so far, five-year-old cars are down 0.8 percent, and 10-year-old cars are down 2 percent.

Put those two months together and the older end of the market looks expensive to own. Using the figures above, a 10-year-old car worth £5,000 at the start of August would be worth about £4,770 now, a loss of roughly £230 in two months (our calculation, and an illustration, not a cap hpi figure). A three-year-old diesel worth £15,000 would be worth about £14,690 after the two diesel falls, a loss of roughly £310.

Solera cap hpi puts the cause down to supply. It said more three-to-four-year-old cars have been coming through disposal channels than at the same point last year, which gives buyers more choice and makes them pickier. Plumb said the tougher part of the market is older, higher-mileage stock, where dealers have to allow for preparation costs and the margin they need when they buy.

Electric cars are the exception. Among three-year-old electric models that gained value in August, cap hpi listed the Polestar 2, up 3.3 percent or £630, the Volkswagen ID.3, up 3 percent or £350, the Peugeot 208, up 3 percent or £250, the Kia e-Niro, up 2.1 percent or £250, and the Renault Zoe, up 3 percent or £215.

Plumb said many used electric cars are now available at prices that make sense to buyers, and that more of them are returning to the market without the fall in values that such a rise in supply might have caused. He added that higher petrol and diesel prices only make that comparison more interesting.

What Comes Next for Used Car Prices

Solera cap hpi expected September to bring a degree of stability, and the three-year-old market has so far followed that, with a 0.3 percent fall against 0.9 percent in August. It also warned that supply usually builds into October as plate-change trade-ins and fleet and rental returns come back to the market.

Excluding 2020 and 2021, the average movement in three-year-old values from September into October has been a fall of 0.1 percent, a pattern that runs back to 2012. Last year values rose 0.2 percent. The older end of the market is the bigger risk, where cap hpi said supply and demand are still out of balance.

Can You Avoid It?

You cannot stop the market moving, but you can decide when and how you sell, and what you buy. These are the steps that make the most difference.

• Sell an older car sooner, not later. Ten-year-old cars lost 2.7 percent in August and 2 percent so far in September, and cap hpi expects supply to build into October. Each of the last two months has cost these owners money.
• Get at least three offers. Compare a free online valuation, a dealer part-exchange figure and an instant-buyer quote, then compare all three with what similar cars are advertised for privately. Offers for the same car can differ widely, so the comparison is worth the time.
• Present the car properly and price it correctly. Plumb said clean, well-presented cars priced correctly are still attracting plenty of interest. A full valet, a set of documents and a recent service history cost little compared with a dealer marking a car down for preparation.
• If you drive a diesel, do the fuel sum before you sell or buy. Diesel costs 23.52p a litre more than petrol in the latest weekly figures, which is £12.93 a tank at 55 litres. A diesel only pays back its higher pump price if you cover enough miles at a good economy figure.
• Buying a used electric car? Get a battery check. A Quotezone survey found 71 percent of drivers would rule out a used electric car next time, 28 percent named battery replacement cost as their biggest worry, and 87 percent would not buy without an independent battery check.
• If the car is on finance, check the settlement figure. The amount you owe is set by your agreement and does not move with market values. Ask your lender for a settlement quote and compare it with the best trade-in offer before you decide.

For buyers, the older end of the market is a chance to negotiate. Dealers need to clear high-mileage stock, and falling values give you room to ask for a lower price, a fresh MOT or a warranty. Check the history, and make sure there is no outstanding finance on the car before you hand over any money.

Sources

• Solera cap hpi, used car values analysis for August 2026 (published 26 August 2026) and September 2026 (published 28 September 2026), as reported by Motor Trade News, including comments by Chris Plumb, head of current valuations at Solera cap hpi.
• Department for Energy Security and Net Zero, weekly road fuel prices, week to 21 September 2026 (petrol 172.01p, diesel 195.53p per litre).
• Quotezone, used electric car survey, as reported by Motor Trade News (2026).