Why should locomotives be held to the same standards as automobiles or heavy trucks? That's like saying an electric power plant should have the same emission standards as a home furnace. Considering the tiny number of locomotives in use compared to cars and trucks, and considering their vast superiority in efficiency, (One stack train could take a couple hundred trucks off the road) I think the current standards are much ado about nothing. I don't think in the big scheme of things, loco emissions are going to have any measurable effect one way or another in air quality. I also don't think there are too many EMD operators dumping a couple of hundred gallons of oil a month in each unit. At the cost of lube oil, that would get prohibitive real quick. I think it is a real credit to the 2 stroke design that they have gotten all the way to tier ll without actually making any monumental changes in the architecture of the power plant. Who knows what might be possible in the future? If effective after treatment of the exhaust is devised, it may not matter that a little oil goes out. People have been trying to bury the pushrod automobile engine for 20 years, yet GM has shown that they can get tremendous power and efficiency in a lower cost, highly reliable powerplant. (A new Corvette pumps out 400 HP, makes 28 MPG, and is so clean, GM was able to remove some of the emissions equipment that was used on 2004 models. All with a 6 liter pushrod motor. I wouldn't write the 710's epitaph just yet. As for the 2 stroke Detroit Diesel, I don't know how much serious emission releated work was ever done to that engine. Detroit decided to go with a modern four stroke design before pollution controls even became a factor in the heavy truck market. I think the decision to dump the 2 strokes was based on the fact that customers had turned against it in the marketplace. They are finicky oil leakers, most are V engines which were never real popular in the diesel market, and the 92 series in particular had some terrible reliabilty problems. I know of a huge truck fleet in my home town that actually got one spare engine for every so many 92 series equipped trucks they bought. That doesn't do much to inspire confidence.