Scrappage schemes are suddenly all the rage, unless you are Vauxhall, which has had one running for months but without pinning it to any emissions-reducing fanfare.

This month, however, BMW, Mercedes and Ford jumped in and now Volkswagen, Audi, Seat, Skoda and plenty more have followed suit. Each scheme has different terms and conditions - of which more later - and each is laudable in some respects of the stated environmental goals, but how much difference do we really expect them to make?

Let’s start with the upsides; vehicle emissions have been pretty hot news since the VW scandal broke two years ago and - finally - these schemes are turning the tide of negative headlines and allowing the car industry to broadcast that modern engines are relatively pretty clean.

​Here are some stats from Ford:

- Diesels from 1993 produce 82% more CO (carbon monoxide) on average than today.

- Petrols from 1993 produce 63% more CO (carbon monoxide) on average than today.

- Petrols from 2001 produce 50% more HC (hydrocarbons) on average than today.

- Average NOX (nitrogen oxides) emissions of all engines in 2001 are 84% higher than today.

- Average PM (particulate matter) emissions of diesels made in 1993 are 96% higher than today.

Latest Society of Motor Manufacturers and Traders (SMMT) figures suggest there are 19.3m pre-Euro 5 cars on UK roads today - the age of vehicle that these scrappage schemes are targeting - so it’s not hard to imagine the benefits of swapping them all for latest generation cars (although, if you can’t, Ford says its the equivalent of 15 million tonnes of CO2 a year, the equivalent to the annual output of three coal-fired power stations).

But - and it’s a big but - how many owners of cars that are worth £2000 or thereabouts (the exact figure depends on the scheme) are about to go out and buy a new Ford, let alone a new BMW or Mercedes? Even at the lowest end of the scale that means swapping a £2000 car for an £12,000 one, but at the top end the suggestion is that a £40,000 car might be a viable exchange for a £2000 one. Yes, comparable lease deals will be available, but in many cases that would likely mean swapping your wheels for a deposit (or part of one) for a three-year loan.