GMC Sierra Owners Manual
Fuel E85 (85% Ethanol)
Vehicles that have a FlexFuel badge and a yellow fuel cap can use either unleaded gasoline or ethanol fuel containing up to 85% ethanol (E85).
See Fuel E85 (85% Ethanol) on page 9‑76. For all other vehicles, use only the unleaded gasoline described under Recommended Fuel on page 9‑74.