I don't usually notice what goes on under the hood. However, in the case of Navistar, I would not purchase a coach unless it was using the DEF fluid to meet pollution requirements. Navistar recently announced they will also use the DEF technology to comply with pollution requirements. Navistar engines currently on the road not using DEF may become "white elephants". Why take the chance?
2005 Newmar KSDP 3910 + GMC ENVOY XUV 37K lbs Moving Down The Road
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Nobody Knows Your Coach Like Somebody Who Owns One Just Like Yours