The 2012 GMC Sierra-2500HD runs on flex-fuel (unleaded/E85).
The 2012 GMC Savana runs on flex-fuel (FFV).
The 2012 GMC Yukon runs on flex-fuel (unleaded/E85).
The 2012 GMC Canyon runs on regular unleaded.
The 2012 GMC Acadia runs on regular unleaded.
The 2012 GMC Terrain runs on regular unleaded.
The 2012 GMC Sierra-3500HD runs on flex-fuel (unleaded/E85).
The 2012 GMC Yukon-XL runs on flex-fuel (unleaded/E85).
The 2012 GMC Yukon-Hybrid runs on regular unleaded.
The 2012 GMC Savana-Cargo runs on regular unleaded.
The 2012 GMC Sierra-1500 runs on regular unleaded.
The 2012 GMC Sierra-1500-Hybrid runs on regular unleaded.
It's worth about $13,000. See quotes at http://www.edmunds.com/gmc/sierra2500hd/2006/index.html