Yes, vehicles will typically have 1,000 to 5,000 miles on the clock.
No, all vehicles are fully warmed up before the test starts.
Tests are conducted using the manufacturer default setting. Often there is only a single setting, but where there is a choice, for example between “normal”, “eco” and “sport”, the default is usually “normal”.
The grade of fuel used follows the manufacturer’s recommendation. For each of regular, premium and diesel, we have a controlled source with the same composition around the year. This includes there being no difference between winter and summer blends. Ethanol content is just under 10% for gasoline.
The weight is equivalent to a driver and adult passenger, plus one child in a child seat and some luggage (around 200 pounds in the back), and a full fuel tank.
The test is 140 minutes long and encompasses a wide variety of road conditions from residential, city, arterial and highway. Each element is repeated a number of times. The cycle was defined having studied typical US driving patterns, and the overall Real MPG is weighted 55% city and 45% highway - the same as the EPA uses. In total, the test is 90 miles long, with average city speeds of 22.5mph and highway speeds of 65mph.
The exterior-mounted parts of the test equipment (the flow meter, heated line and exhaust pipe connection) are installed at the rear of the vehicle and as low down as possible to minimize any aerodynamic effects. All windows are left up throughout the test. Wind tunnel tests indicate that the effect is very low, with no significant reduction in fuel consumption being seen.
Each element of the test is repeated, with air conditioning off and then with air conditioning set manually to maximum. The difference in engine load between the two is then calculated. The Real MPG result assumes an average air conditioning load of 50% of maximum overall.
The test equipment records the performance of the car second-by-second and that information is used to adjust for unexpected variations in speed or congestion to a common standard between all tests. This ensures comparability between different test results.
Testing does not happen in the wet, high winds or other adverse conditions. Before being measured, the equipment standardizes the gases to 70 degrees Fahrenheit, one Atmosphere of atmospheric pressure and average humidity before being measured.