I'm looking into purchasing a used duramax diesel GMC sierra pickup. A friend of mine has a 2009 Sierra with 50 000 km on it. I'm not familiar with this engine so I wanted to ask a few questions about it. 1. What can I expect in terms of fuel economy? 2. What can I expect in terms of durability? 3. Are the maintenance costs going to surpass any fuel savings I'd get from going with a gas pickup? He's asking $41K for it. The truck cost him almost $60K in 2009. All prices are in Canadian dollars. A new 6.0L gas 2011 Sierra similar to his goes for about $42K (after rebates) + tax. Thanks, in advance, for all replies.