Why would tier 4 engines be more fuel efficient? Lets see, hmm they said the same thing when tier 3 came out over tier 2? Also taking into account where all this info is coming from about global warming..... so who actually believes that this is coming from scientists. Actually more appropriately activists - so when it comes down to it - 2011 fuel bills will be worse than now. That's great, consume more energy and accomplish less. Global warming and emissions contributing to it is the biggest farce ever dreamed up by mankind. This will be the unifying issue that brings about a one-world government in the end times! It's all about control!