Peter Banks was driving down a busy freeway flanked by traffic on the outskirts of Adelaide when his car suddenly lost acceleration.

Key points: Lawyers are anticipating multiple class actions against car dealers over diesel particulate filter (DPF) issues

Lawyers are anticipating multiple class actions against car dealers over diesel particulate filter (DPF) issues DPFs are meant to trap and burn emissions

DPFs are meant to trap and burn emissions Instead, drivers are being told soot is building up because they are not regularly driving their cars on open roads

"All the cars around me are going really fast. The ones on my right are going very fast, the ones behind me are banking up, and on my left there's a number of semi-trailers going down the slow lane," he said.

"I was absolutely stuck, I was quite flummoxed."

After he managed to manoeuvre his Volkswagen Tiguan through the traffic and onto a suburban street, he and his wife realised thick white smoke was pouring from the exhaust.

"We managed to get around the corner and pulled over quickly and jumped out of the car, convinced that it was about to burn, or catch fire or explode," he said.

But the car did not explode, or catch fire.

He was later told it was doing exactly what it was designed to do — burning off pollution that had clogged up in the diesel particulate filter (DPF).

DPFs are supposed to trap and burn off diesel emissions, both to protect public health and to comply with standards.

Instead, drivers and some people working in the car industry say the filters are clogging up, causing putrid smoke to spew out of exhausts and costing fuel efficiency.

In some cases, as happened to Mr Banks in July, the DPF warning light comes on, the car goes into limp mode and needs to be towed.

More class actions to come

Earlier this year, the ABC revealed allegations of nationwide problems with the DPFs in the best-selling Toyota Hilux, Prado and Fortuner cars.

Now other car manufacturers are being caught up with what has been described as a "widespread" issue with the filters.

Lawyers running a class action against Toyota, alleging it sold consumers cars with faulty DPFs, said they had been contacted by dozens of drivers of other well-known brands reporting similar problems.

"There's been a lot of registrations from other manufacturers' vehicles such as Range Rovers or Land Rovers, Subarus, there's been a Porsche [and] there've been Volkswagens," Charles Bannister from Bannister Law said.

Dozens of frustrated drivers have also contacted the ABC.

Peter Lynch has been tracking his fuel consumption to work out how well his diesel particulate filter is working. ( ABC News: Mary Lloyd )

Peter Lynch keeps a detailed log of his fuel consumption, so he can regularly "clean" his DPF as his use of fuel increases. ( ABC News: Mary Lloyd )

Peter Lynch, a mechanical engineer from Dorrigo in NSW, came up with his own solution to keep his DPF clean after five years of attempting to get his car fixed.

He monitors his fuel efficiency and once it declines to a certain point, he puts his Subaru Forester into second gear and drives it at 60 kilometres an hour for about 30 minutes.

He said the high revs, or revolutions per minute, pushed oxygen through the engine, which then made its way through the DPF and cleared out the accumulated soot.

"I've had vehicles for over 30 years and this is the most unreliable vehicle I've ever had, but we've kept it because now we've found a solution," Mr Lynch said.

"It's lovely to drive when it's operating well, but there's no way I'd buy another diesel vehicle.

"I just think the future of diesel vehicles with these emissions standards that are being implemented, are doomed."

'We were absolutely astonished'

Lawyers say drivers are being left with cars that have higher running costs than they had originally anticipated.

Mr Bannister anticipates launching multiple court cases against up to six car brands.

Charles Bannister's firm has heard from thousands of Toyota drivers, and dozens of drivers from other companies. ( ABC News: Mary Lloyd )

"It's quite likely, given the growing number of registrations [over] other manufacturers and the way in which we see those manufacturers are dealing with consumers," he said.

Mr Banks, who regularly drives his car to Melbourne with his wife to visit his grandchildren, said his car had been fuel efficient and reliable for the past six years.

But after the incident on the freeway, he had to have it towed first to the home, then to the VW dealership.

He said the mechanic then drove it around for 15 minutes, before telling him: "It's alright now, that was the engine management system detecting that you had a bit of a blockage."

"We were absolutely astonished and I was actually quite annoyed by this stage because I had to pay $160 for the privilege of being told that the engine and the car was doing what it was designed to do," he said.

"We had no idea, we've had it for six years and this is the first time it's happened … I could have had an accident coming down the freeway."

When the ABC contacted Volkswagen about Mr Banks's car, they offered to refund the $160 and to inspect his vehicle again.

"We can say categorically that there is no systemic history of customer complaints regarding the DPF on this model," a Volkswagen spokesman said in a statement.

The company spokesperson said they were of the opinion the build-up was caused by an overfill of oil and a separate fault.

The Australian Aftermarket Automotive Association (AAAA) represents independent mechanics. The organisation's chief, Stuart Charity, said his members were seeing an increasing number of people with DPF problems.

He said drivers were coming to independent mechanics after being told by dealerships the problem was the way they were driving the car.

That claim supported the accounts of drivers who told the ABC they had been blamed for not taking their diesel cars on long trips to generate the amount of heat required to burn off soot in the DPF.

Peter Lynch says his car is lovely to drive when it's functioning, but it's also the most unreliable vehicle he's ever owned. ( ABC News: Mary Lloyd )

"They said we needed to do more country driving," Mr Lynch said.

"The reality is we live in the country. All our driving is country driving."

When the ABC approached Subaru about reported DPF issues, it stated there had been "no Diesel Particulate Filter-related recalls since sales began in 2009".

The solution is 'not to sell diesel cars'

Mr Charity said if consumers were not being warned about the need to clear the DPF, car manufacturers were effectively selling vehicles that were not fit for modern driving conditions.

He also said that had created a black market for alternatives.

"They're pushing people away from dealerships, saying 'no issue here' and forcing customers to look for other alternatives," Mr Charity said.

"You've got these quality issues, reliability and durability issues, you've got the high cost of replacing the DPF filter and a lack of government action and oversight.

"All of those are converging to create a black market for DPF deletion."

DPF depletion involves reprograming the cars to bypass the emission control system, causing dangerous noxious gases to be pumped into the atmosphere.

"Quite frankly it's horrendous," Mr Charity said.

"We've been trying to educate our industry not to do this — that it is illegal."

Operators are blatantly advertising the service without fear of enforcement, something Mr Charity has urged regulators and police to shut down.

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He believes the future of diesel cars is under a cloud.

"The long-term solution is probably not to sell diesel cars in Australia," he said.

"There's a real problem with the technology, but that's not going to help people who own diesel cars now."

In the meantime, he called on the Government to compel manufacturers to fix the vehicles.

"The solution … is for the Government to step in and force the car makers to step in and rectify the quality and durability issues on their vehicles and to honour their Australian Consumer Law obligations," Mr Charity said.

"Car manufacturers need to back their product. They should be fit for purpose for Australian conditions and for the requirements of the driver they are selling them to. And if they're not, they should fix them."

The ABC contacted Subaru, Volkswagen, Land Rover and Porsche for comment about DPF complaints.

Porsche said it had not offered diesel cars for sale since February 2018. Volkswagen maintains DPFs are unlikely to be a problem if people regularly drive on motorways.