If you want to delve into the conspiracy fueled reason why we still aren't away from oil...key gov't personnel have interests in large oil companies...discuss. Go!
Weight loss is one possible solution and yes, GM needs to lose pushrods, except in high performance, specific vehicles (ie, Vette, Camaro) but in the Impala, use an ohc engine, compare fwd vs rwd fuel economy, make it flexfuel with cylinder shutoff. Cut back on the huge power drains in car amenities use. Make it so you have to order that GPS or AC again, like it was in my grandparent's time. Whatever the solution may be, it will cost money and take time, neither of which the major car companies of the USA seem to have, all leading back to money. Sorry for the long rambling post, I am exhausted.