There is magic around the 10% solution. I expect many fleets and OEMs have sat through many presentations, read many articles and reports where the claim of a 10% improvement in fuel economy is supposed to wow.
My guess is that 10% is where the venture capitalists and fleet customers seem to get interested in an idea, where 9% or 6% or 3% just are not attractive enough to raise an eyebrow.
How much of those 10% claims do fleets actually see in their real-world operations?
That question has no easy, single answer. I’ve spent a considerable part of my career in this industry trying to understand the differences between controlled test results and the real world.
The fundamental challenge is that repeatable tests — those that arrive at nearly the same answer each time — require controlling a lot of variables. Those variables include the weather, the vehicle, the driver, the load, traffic, time of day, etc. Test engineers have to simplify tests by controlling many of these factors. For example, traffic and grades need to be identical for each test, so testing is done on a track with no traffic. Weather is very unpredictable, so testing is done in rare, nearly still wind conditions where the ambient temperature is moderate.
Other factors are controlled by attempting to cancel them out. For example, each trailer is unique. A tractor test looking at fuel economy versus a baseline vehicle will be run at the same time of day at the same track. To eliminate any bias caused by factors unique to each trailer, the tests will be done twice, with the trailers swapped between the two tractors. Near-zero wind conditions are very hard to find, and grade variations are typical, so tests often are conducted in both directions on a road or track, hopefully cancelling out any bias that the direction might induce in the results.
Other factors, called transients, are minimized, trying to operate the vehicle as steadily as possible.
