The CI Co-Op is the new provide of fuel for a number of States departments.
The new deal was agreed in December 2023.
The States say it will 'offer better value for money and more flexible locations for filling up.'
Currently it applies to vehicles run by Guernsey Water, Health and Social Care and Education's Pupil Transport Service.
Previously, these departments had used a locally run garage.
It's unclear whether the agreement covers States Works, which operates a large and diverse fleet.

Firefighters tackle gorse fire at La Corbiere
50 people evacuated from scene of fire in Portbail-sur-Mer
'Pause before paying' to avoid being scammed, islanders urged
Five Guernsey firefighters injured while travelling to assist with Sark fire
Emergency response to fire on Little Sark
Hospitality sector calls for Guernsey's States to make savings before GST
Bailiwick's underwater wonders highlighted on new stamps
"Heightened risk" of wildfires in Guernsey