The simplest way to check E85 content. 9$ bottle online. Add water/fuel to the fill lines. Shake and wait. Though this was pretty neat. : r/Justrolledintotheshop
REV-X E85T0501 E85 Gasoline Tester - Easy to Use Ethanol Test Kit – PartLimit
Carburant - Que vaut la conversion au superéthanol E85 ? - Actualité - UFC-Que Choisir