> In the last 10 years alone, engine efficiency gains are really being made. I work with people who literally do this stuff. Not all improvements that can be ma

> In the last 10 years alone, engine efficiency gains are really being made. I work with people who literally do this stuff. Not all improvements that can be made have yet been made. It was just 2007 that VVT was used in Caterpillar diesel engines Tellingly, Cat doesn't do on-road diesel engines anymore, and hasn't for years... largely due to the inability to produce maintainable, efficient engines and meet legislative demands for clean air. My opinion, they could've stayed in the game but saw where the game was headed and decided to let others take the pain. Old Cat 13 and 15 engines were sought after for a time after production stopped, exactly because of their reputation for reliability and maintainability. The most notable changes in the diesel engine scene lately has not been VVT but instead the bolt-on addition of SCR for Tier 4 legislation, which does indeed make the emissions cleaner (when it works) but at the expense of maintainability. > If anybody can innovate in this area, Volvo are a good candidate. I appreciate the enthusiasm and I agree there may be engine improvements yet to be made, but I am quite wary of anyone saying significant improvements are ahead while not costing the owner or the supply system more in total over the long run.