When did DEF become required ?

Other than the ULSD issue in Mexico, the newer motors have some advantages. Dealing with DEF isn't really a big deal. Every so often you pour some in. It's fairly cheap, both in cost to purchase and in cost per mile. Heck, you already do that with windshield washer fluid.

2006/2007 is the last model years for non-ULSD and non-DPF. The motors had to be made in 2006, but for some models (like my Fuso) they made all the 2007 model year motors in 2006. If you plan on going to Mexico or points further south, being able to take the non-ULSD becomes important.

Mr. Dave, we bought the first year coach with the particulate filter on the 2007 chassis (2008 coach). We have had zero problems with it. DEF came out in 2010 if I'm not mistaken and our new coach will have it. I'm not concerned. The word on the street is the DEF units get a little better fuel mileage.

We have no smoke come out on heavy hill climbs. The regeneration cycle happens once about every 10,000 miles. There is a light on the dash to tell me the process is starting/happening.

If you want a totally emission-free diesel vehicle, go 2006 or earlier. It's funny, I remember when people were going crazy when the catalytic converters came out in 1975..... and fully implemented in '79-'80. Same happened with shoulder seat belts with the buzzers.

Go with the environmentally friendly units. Save a tree. LOL! (just kidding). Buy and drive what you like, this is America.

A side note: Before catalytic converters, the Los Angeles smog was horrendous. You couldn't see houses off the I-10 Freeway, especially, in San Bernardino, CA. There is still some smog but 95% better. Low emission vehicles are important for our health.
MM.

IIRC Jan. 2010