The main thing to remember is that prior to the EPA-207 standards you could run any diesel fuel. The EPA-2007 standards took effect Jan 1, 2007 but that was for engines produced as of that day. Most RV manufacturers bought enough in advance to finish out the 2007 model year with pre-2007 standards. That generally happened around May 2007 - give or take.
The EPA-2007 engines required Ultra Low Sulphur Diesel fuel (ULSD) and had Diesel Particulate Filters. The DPF would foul if standard Low Sulphur Diesel (LSD) was used so you had to use ULSD as well as the newer API-CJ engine oils, which had less ash content.
The EPA-2010 engines are just now coming into play. Just when depends on the manufacturer and coach model. If they guessed right their projections were good. For instance, the Allegro Bus is now the number 1 selling diesel pusher for 2009. Previously the Phaeton was number one but now it is number two. This wasn't expected so they ran out of pre-EPA-2010 engines and any Allegro Bus orders placed recently will be for the newer EPA-2010 engines - which will have a $17,500 hike to the list price. But, the Phaeton is in good shape and will have the older engines up into May. So each coach will vary from another model or brand as to availability.
The EPA-2010 engines generally use SCR emissions technology. This means that urea will be injected into the exhaust system's recombiner from a small 6 gallon tank. You will now have to buy gallon jugs of urea - which is technically called Diesel Emissions Fluid (DEF). DEF is 37.5% ammonia and the rest is water. Some engines, such as Navistar's MaxxForce engine and the Cummins ISX will use extensive exhaust gas recirculation instead of SCR but the Cummins ISB, ISC, and ISL, which make up the vast majority of RV diesel engines currently being used, will use SCR so owners of these newer engines will have to deal with the urea issue.
Mark & Leann Quasius
2016 Cornerstone 45A
2007 Allegro Bus 42QRP (Sold)
2012 Jeep Wrangler Unlimited - Rubicon