Reading fuel-saving claims
Explainers on the questions that decide whether a fuel-saving claim is worth anything — written because we could not find honest answers elsewhere, and in one case because we got it wrong ourselves first.
Why “20% better” is not “20% less fuel”
+20% → −16.7%Efficiency and consumption are reciprocals. A 20% gain in km/L is a 16.7% cut in fuel; a 43% gain is 30%. The conversion, where the confusion does real damage, and the mistake that sat in our own analysis for weeks.
Read the explainer →Where fuel-saving products actually intervene
Fuel · oil · airEvery product sold to a fleet acts at one of three points. The point of intervention decides what it can plausibly do — and what evidence should exist for it. Mechanisms compared, not percentages.
Read the explainer →How to measure fleet fuel consumption
L/100 km · full tankThe full-tank method, which fuel data to trust, a monthly report that shows real changes — and five things from our own records that fake or hide a saving. With a report template to download.
Read the explainer →Carbon tax on diesel by country
Tax · trading · noneHow a carbon price reaches diesel — as a tax or through emissions trading — what it adds per litre in selected countries and US states, from well under one euro cent to about 41 euro cents, and how a fleet can estimate its own carbon cost.
Read the explainer →A decarbonisation strategy for a diesel fleet
Measure · fewer litres · fuel · replaceWhat a fleet can do with the vehicles it runs today, in order of the capital needed — and where an air-filter treatment fits, with what our trials show and what they do not.
Read the explainer →Five pieces, because we would rather publish a few that are worth reading than ten that restate the evidence pages. The rules by region are summarised on regulatory context, and how a trial should be run on measurement methodology.
What would you want explained?
If you are evaluating this product category and there is a question the evidence pages do not answer, tell us. That is how the first two came about.