If you own a diesel car, passing an MOT is about to become an even bigger nightmare, thanks to new MOT rules coming into effect from May.
All vehicles will be put through tougher emissions tests, with faults rated in three defect categories: dangerous, major and minor.
Cars with minor defects will have their faults recorded, but will be allowed to pass. It's an automatic fail for those in the dangerous category.
For diesel cars specifically, cars fitted with a filter that gives out "visible smoke of any colour" will be issued with an automatic fail. Furthermore, any vehicle that has a DPF that looks as if it has been removed or tampered with will not pass - unless it can be proved it has been done so for filter cleaning.
The Driver and Vehicle Standards Agency has also included new criteria related to steering. A steering box leaking oil would get a minor fault, but if it drips badly, it will be pushed up to a major rating, and subsequently fail.
Also, reverse lights will be checked and brake discs also inspected to see if they are "significantly or obviously worn".
The new rules will start from May 20, but an RAC spokesman said they feared that splitting up the criteria of defects into three categories could end up confusing motorists.
He said: "Rather than MOT failures simply being black and white, the new system creates the potential for confusion as testers will have to make a judgement as to whether faults are Dangerous, Major or Minor.
"Motorists may also struggle to tell the difference."