Found this old photo of my lovely wife and me aboard the train back in 1995. I don't appear to be too happy about it for some reason. Maybe I just didn't want my photo taken.
They started out converting them to a mix of 40% diesel and 60% natural gas. Then in 2008 they went to 100% compressed natural gas (CNG). At first it was deemed necessary to include the diesel for lubrication properties. Somehow they get around this now. Perhaps they improved the distribution of crank case oil like is done in gasoline engines. The CNG tanks are in the box car between the two locomotives. At least one of the locomotives has been modified with an EMD 12-645E3 prime mover.