This hits close to home.
As an Excavation and Concrete contractor, I have the responsibility of owning a fleet of vehicles and machinery. The "fleet" breaks down into 3 categories.
Trucks/Autos (Crew trucks, haul trucks, light trucks)
Machinery/Heavy Trucks (backhoes, crawlers, water trucks, dump trucks, skid steers, forklifts etc.)
Small Equipment but still heavy duty(Light towers, various trowel machines, survey equipment, compressors, jack hammers, generators)
Our newest vehicle is a 2013 Toyota Tacoma, which is my truck. The rest of the truck/auto fleet is between 2001 and 2010, simply because it is all diesel vehicles. We are able to maintain them without much issue.
The worst problem we ever had was with the 2003-2006 Ford 6.0 liter diesels which were the first generation of low emission diesels Ford made after they discontinued their legendary 7.3 liter power stroke(of which we still have a few). The 2003-2006 Fords suffered mostly from a bad oil cooling design and subsequent high exhaust gas temperatures which subsequently destroyed the EGR. The EGR's were replaced numerous times under warranty until the warranty expired. The trucks continued to have problems due to the oil cooling issue (Ford designed the oil cooler to be a coolant/oil heat exchanger-due to the tight quarters of the oil cooler, the coolant would eventually congeal and the exchanger would not operate properly and eventually the first thing that would give out would be the EGR if you were lucky. These trucks were notorious for for blown heads and other catastrophic related engine failures.)
Fortunately for us we kept a close eye on them and never had any catastrophic problems before we decided to replace the oil coolers and EGRs with aftermarket parts. The aftermarket oil cooler was particularly clever, in that it disposed of the old cooler and replaced it with a dummy filler which rerouted the oil to an air cooler mounted in front of the radiator. We did that work back in 2012 and the rucks have been great since. We have even considered buying these vehicles and fixing them for pour fleet because they can be had so cheaply, but decided against it as there is a risk that serous unknown damage may be lurking in the background.
Anyway. New trucks =bad. Old trucks=good.