Are low emission cars more difficult to get through MoT when older?

EdGasket

I am thinking petrol here rather than diesel but I guess the question can apply to both. So if a new car has low emissions and low tax e.g. £30 a year instead of over £100 then does that mean it requires more maintenance and cat replacements when older to get it through (presumably) tighter emissions in the MoT for the make and model?
Anyone have any experience of MoT pass or failure on a low-emission car?

daveyjp

Petrol MOT doesn't test CO2 emissions, only CO and hydrocarbons.

There is a very narrow range of acceptable CO emissions (most are 0.3 or 0.5 max reading) depending on car, whether it be a 900cc city car or a Ferrari V12.

Joe_Horner

As Davey says, "low emission" as it relates to car tax is ting at all to do with MOT because the car-tax version of emissions is just the same figure as fuel consumption converted to a politically invented figure to make it look scary. It's why they're pretty well meaningless - by far the biggest factor affecting "CO2 emissions" is driving style, but if they tried to tax that then people would complain.

The MOT is concerned with emission of "real" pollutants such as carbon MONoxide and unburnt fuel - things that are going to take a lot less than hundreds / thousands of years to kill you and those bear virtually no relationship to fuel consumption.

EdGasket

OK but would the car have more stringent MoT test limits? After the BET test, if a car fails, it is then tested against model-specific limits; I assume, but may be wrong, that these are tighter for a low emission car than for one that was more pulluting when new?

Joe_Horner

No, the vehicle specific will be much the same because "more polluting" according to VED emissions is nothing at all to do with pollution as tested in the MOT.

VED "more polluting" means "higher CO2 output", or "higher fuel consumption" in real terms and takes no notice of CO, NOx or hydrocarbons.

"More polluting" in MOT terms means higher output of CO and hydrocarbons but takes no notice of CO2 (fuel consumption) or NOx (one of the REAL nasties).

Richard53

The OP may be mixing up VED and MoT, but there is a valid point there. The emissions level tested for in the MoT depends on the year of manufacture, and gets tighter the newer the car is. If cars are producing less pollution year on year, the MoT test is likely to become stricter for those vehicles, and may be very expensive to get through the test once the car is 10+ years old.

One of the reasons I like older cars is that MoT time is more relaxed. At its last test, my Merc had 0.01 CO (limit 3.5) and 55 HC (limit 1200), so I know that it is well within its limits and shouldn't give any trouble at MoT time for a while yet - in emissions terms at least. With modern cars, testers are referred to the manufacturer's figures for when the car was new. In ten years' time, what's to say that any deviation from that will be a fail?