GM color codes the fuel cap green to indicate clean Ultra Low Sulfur Diesel (ULSD) or B5 (5% biodiesel) fuel only. Good news: For 2008, GM will be tweaking the fuel system to allow up to B20 (20% biodiesel). Initially this will be for fleet vehicles only, but the door is now open for all Duramax engines to use higher biodiesel blends.
Read more: 2007 Chevrolet Silverado 2500HD Duramax test drive and review
Read more: 2007 Chevrolet Silverado 2500HD Duramax test drive and review