01/06/2026
Just failed the MOT on emissions? Before you book it in for expensive diagnostics, it's worth understanding what those numbers actually mean.
On a petrol car the tester is looking at CO (carbon monoxide) and HC (hydrocarbons). Both tend to climb when combustion isn't clean — carbon deposits building up in the fuel system and combustion chamber, and dirty injectors with poor spray patterns.
Forte Petrol Emissions Reducer goes in the fuel tank and uses PEA (polyetheramine, a powerful fuel-system detergent) to clean those deposits out of the fuel system, combustion chamber and exhaust — and the catalytic converter too — so combustion tidies up and the readings come down.
The trick is timing: add it to a full tank 100–200 miles before your retest so it's had chance to work. Changing the oil and filters at the same time helps too.
It won't magic away a mechanically failed cat or a sensor fault — but for a borderline emissions result it's a sensible first step → https://www.bmwtoolrental.co.uk/petrol-emissions-reducer