The diesel ITV opacity plate: from serious defect to worthless paper
The opacity plate required at Spain's ITV roadworthiness test was a serious defect from May 2018, but a draft removed it. The emissions test has still been tightened and drivers…
English · Original discussion in Spanish · Published
The diesel ITV opacity plate: from serious defect to worthless paper
Do I need the opacity plate in the engine bay to pass the ITV (Spain's roadworthiness test)? For months, the official answer was yes, and anyone without one risked a minor defect from 20 May 2017 and a serious one —failing the inspection— from 20 May 2018. The warning spread like wildfire through motoring forums. The plate, a small metal square showing the approved absorption coefficient, became the new enemy of the old diesel driver. Months later, a draft of the ITV manual removed that consideration: not carrying it would no longer be a defect. The scare, however, exposed something more uncomfortable: the emissions test had genuinely been tightened.
What the opacity plate is and why it became a problem
The plate shows the smoke absorption coefficient the vehicle was homologated with. It is the legal opacity limit the exhaust may emit. Without that reference, testers apply standard values based on the year of registration. The problem came with the 2016 regulatory change: lacking the plate became a minor defect first, and a serious one later. For an ageing vehicle fleet, that meant a car running perfectly could fail its ITV over a lost metal plate.
The reaction was swift. By April 2017, the conversation already revolved around what counted as an "old diesel" and the suspicion that the noose was tightening around engines without particulate filters. Renault's response to an individual enquiry was revealing: the brand let on that it had been agreed to remove the minor or serious defect classification for not carrying the plate, pending official confirmation from the ministry. The later draft of the ITV manual confirmed the U-turn. The plate stopped being a problem. The opacity test, not.
The emissions test: the real wall of the diesel ITV
The tightening of opacity measurement had been in force since June, even before the plate furore. The test measures the smoke coming out of the exhaust under load, with the engine revved hard. And there the margins narrowed. A 2004 vehicle with a limit of 0.8 could fail while a newer one with a higher limit passed without trouble. One driver summed up the paradox: his 2004 diesel, with lower measured emissions, would be branded a super-polluter, while a dirtier one would drive around freely.
Inspection data paint an uneven picture. A 2005 diesel with a 1.2 plate passed at 0.5. An Xsara Picasso with a 1.8 limit had no problems. A 15-year-old van with 285,000 kilometres read 0.97 and passed "by a hair", when in previous ITVs it had registered 1.85. Another vehicle homologated at 1.5 read 2.15 and passed because its limit was 3. The range is enormous and depends both on the engine's condition and the year of homologation.
What drivers do to pass the test
The list of tricks is long and has been refined over the years. The most repeated: hard revving in neutral before entering the inspection lane, with the engine properly warm. Add to that a new air filter, freshly changed oil, premium diesel and anti-smoke additives mixed with little fuel. Some stick the petrol station's pressure washer lance into the exhaust pipe and scrape off the stuck-on soot with a rag held in pliers. The logic is simple: what comes out at the ITV is what's stuck to the pipe, not what the engine generates under normal conditions.
Results vary. An urban delivery van went from 2.00 to 0.8 in three days after cleaning the exhaust. Another, after six months and 3,000 kilometres in the city, jumped from 0.67 to 2.80. The same van, with a prior cleaning, additives and two litres of 98-octane petrol in a 60-litre diesel tank, dropped to 0.58. Some simply slacken the accelerator cable so the pump never reaches full and record zero opacity. And some, quite simply, drive without mercy: 0.11 on a 12-year-old diesel with 234,000 kilometres.
The real cost: what lies behind the tightening
The underlying issue, according to one participant, is a fiscal and regulatory policy that favoured diesel for decades. Diesel was cheaper to protect a European industry and hold off Japanese and American competition. Now, those same vehicles poison the air more and the authorities are going after them. The deeper suspicion, he adds, is that the next target will be something else: LPG, lithium batteries or whatever comes next.
Meanwhile, manufacturers are not abandoning diesel. Ford announced diesel engines for the F-150, the best-selling model in the United States. The contradiction is obvious: diesel is penalised in Europe while being launched in America. And drivers, caught in the middle, do the maths. You don't swap a 13-year-old car for pleasure. You swap it when there's no other choice.
The opacity plate turned out to be worthless paper. The emissions test, not. And while testers keep measuring the smoke coming out of the exhaust, drivers keep looking for ways to get their old diesel past the cut. With these rules, it's a wonder anyone is surprised that people stretch their car's life to the limit.
Do I need the opacity plate in the engine bay to pass the ITV (Spain's roadworthiness test)? For months, the official answer was yes, and anyone without one risked a minor defect from 20 May 2017 and a serious one —failing the inspection— from 20 May 2018. The warning spread like wildfire through motoring forums. The plate, a small metal square showing the approved absorption coefficient, became the new enemy of the old diesel driver. Months later, a draft of the ITV manual removed that consideration: not carrying it would no longer be a defect. The scare, however, exposed something more uncomfortable: the emissions test had genuinely been tightened.
What the opacity plate is and why it became a problem
The plate shows the smoke absorption coefficient the vehicle was homologated with. It is the legal opacity limit the exhaust may emit. Without that reference, testers apply standard values based on the year of registration. The problem came with the 2016 regulatory change: lacking the plate became a minor defect first, and a serious one later. For an ageing vehicle fleet, that meant a car running perfectly could fail its ITV over a lost metal plate.
The reaction was swift. By April 2017, the conversation already revolved around what counted as an "old diesel" and the suspicion that the noose was tightening around engines without particulate filters. Renault's response to an individual enquiry was revealing: the brand let on that it had been agreed to remove the minor or serious defect classification for not carrying the plate, pending official confirmation from the ministry. The later draft of the ITV manual confirmed the U-turn. The plate stopped being a problem. The opacity test, not.
The emissions test: the real wall of the diesel ITV
The tightening of opacity measurement had been in force since June, even before the plate furore. The test measures the smoke coming out of the exhaust under load, with the engine revved hard. And there the margins narrowed. A 2004 vehicle with a limit of 0.8 could fail while a newer one with a higher limit passed without trouble. One driver summed up the paradox: his 2004 diesel, with lower measured emissions, would be branded a super-polluter, while a dirtier one would drive around freely.
Inspection data paint an uneven picture. A 2005 diesel with a 1.2 plate passed at 0.5. An Xsara Picasso with a 1.8 limit had no problems. A 15-year-old van with 285,000 kilometres read 0.97 and passed "by a hair", when in previous ITVs it had registered 1.85. Another vehicle homologated at 1.5 read 2.15 and passed because its limit was 3. The range is enormous and depends both on the engine's condition and the year of homologation.
What drivers do to pass the test
The list of tricks is long and has been refined over the years. The most repeated: hard revving in neutral before entering the inspection lane, with the engine properly warm. Add to that a new air filter, freshly changed oil, premium diesel and anti-smoke additives mixed with little fuel. Some stick the petrol station's pressure washer lance into the exhaust pipe and scrape off the stuck-on soot with a rag held in pliers. The logic is simple: what comes out at the ITV is what's stuck to the pipe, not what the engine generates under normal conditions.
Results vary. An urban delivery van went from 2.00 to 0.8 in three days after cleaning the exhaust. Another, after six months and 3,000 kilometres in the city, jumped from 0.67 to 2.80. The same van, with a prior cleaning, additives and two litres of 98-octane petrol in a 60-litre diesel tank, dropped to 0.58. Some simply slacken the accelerator cable so the pump never reaches full and record zero opacity. And some, quite simply, drive without mercy: 0.11 on a 12-year-old diesel with 234,000 kilometres.
The real cost: what lies behind the tightening
The underlying issue, according to one participant, is a fiscal and regulatory policy that favoured diesel for decades. Diesel was cheaper to protect a European industry and hold off Japanese and American competition. Now, those same vehicles poison the air more and the authorities are going after them. The deeper suspicion, he adds, is that the next target will be something else: LPG, lithium batteries or whatever comes next.
Meanwhile, manufacturers are not abandoning diesel. Ford announced diesel engines for the F-150, the best-selling model in the United States. The contradiction is obvious: diesel is penalised in Europe while being launched in America. And drivers, caught in the middle, do the maths. You don't swap a 13-year-old car for pleasure. You swap it when there's no other choice.
The opacity plate turned out to be worthless paper. The emissions test, not. And while testers keep measuring the smoke coming out of the exhaust, drivers keep looking for ways to get their old diesel past the cut. With these rules, it's a wonder anyone is surprised that people stretch their car's life to the limit.
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Summary of a discussion on Burbuja.info - Foro de economía, actualidad y política., translated from Spanish and reviewed before publication. Read the full discussion (86 replies).
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