Although most of the media attention has been focussed so far on Volkswagen's admitted use of a defeat device on roughly 480,000 cars in the US, and 11 million worldwide, equipped with the EA189 turbo-diesel engine, which detects when the car is being tested under lab conditions, there has also criticism of the government agency that was hoodwinked.
In response, the EPA announced on Friday afternoon (US time) that it would begin doing spot checks on manufacturers' vehicles and that it would use "driving cycles and conditions that may reasonably be expected to be encountered in normal operation and use".
Chris Grundler, the director of the Office of Transportation and Air Quality at the EPA, told The Wall Street Journal: "We aren’t going to tell them what these tests are, they don’t need to know. They only need to know we will be keeping their vehicles longer and driving them more."
The director added that the EPA's actions will be done in co-ordination with Canadian authorities, and that it has begun spot checks of 2015 and 2016 model year diesel cars, including rental vehicles.
According to the organisation, these new ad hoc tests have been implemented to detect any potential defeat device, as well as deter their future use.
Automakers have been warned that these additional tests may delay certification for their cars and that test vehicles will incur additional mileage.
The new tests will be done in addition to the current regime of lab tests to calculate emissions and fuel economy.
Some European nations and other countries have expressed a willingness this week to toughen their certification and verification processes around car emissions in the wake of the Volkswagen affair.
You can read the EPA's notice to all car makers here.