I have various equipment. Everything I have works very well. I try to keep up on maintenance: could be a bit better, though not likely much.
My Kioti, Tier IV, has run flawlessly, now 700 hrs: I've had non-engine issues which, thankfully, were dealt with through warranty. Folks should go back and see what folks were saying about the future for Tier IV machines in 2016 (when I got my Kioti). Many probably were forecasting utter disaster; yet, with 700 hrs on my Kioti there has been no such disasters (yes, some folks have had problems; there has been problems with everything, statistics tell us it's to be expected, and it's why warranties exist- to cover statistical anomalies).
Of everything I have, I regularly marvel at, and praise the most, my VW TDIs (ALH engines) the most. Computer controlled mechanical injection pumps. EGR valves and coolers have been left on all my TDIs: most cars I've gotten I've had to clean (four out of six? one was from a fellow TDI enthusiast who had already done the work), but once done zero issues. My car is 21 years old, nearing 220k miles and is getting (currently) over 55mpg and over 800 miles to a tank of fuel: I've logged just over 100k miles of fuel consumption and am averaging 51.5 mpg. Larger nozzles and a tune (the beauty of computer stuff is the ease in which fueling behaviors can be altered): it's a lot peppier than stock while still cranking out insane fuel mileage. I do all the work on these cars myself, but, the engines themselves require almost nothing (once I've gotten them up to my preferred spec it's then only a matter of regular maintenance on them, the engines).
My old 1993 Ford IDI (International diesel) puked a head gasket so I got a 1994 Dodge Cummins. The legendary 5.9L 12v, all mechanical. Can't say that it's any more or less reliable than anything else I have: it's not used a lot, so when it's needed it HAS to work.
My
B7800 Kubota is the worst starting of all my diesels (my last valve adjustment probably made it worse!), but it otherwise works flawlessly. Stinky compared to my Kioti. But it nonetheless has its role and does it well as always.
And even my clatter-box Polaris Brutus just flat out works. The 24hp Yanmar is the noisiest thing on the planet. As long as the battery is charged (which is STILL the original from 2013!) it will fire right up. I have more concerns over this thing than anything else (I even my less concern that with my far more complex generator, which is circa 1993 [it's the electrical stuff that makes me a bit nervous, though I've ironed out all the issues with that; the Kubota engine is to die for for this application]).
Harry, I had an issue with water in my Kioti's fuel when I first had it. I went through everything I had looking for water, expecting my fuel storage tank to be the culprit, but nothing showed any water! It was the stupid cheesy/crappy locking fuel cap, letting rain water into the tank: dealer gave me a new, better one and the water issue has never resurfaced. I couldn't prove that it was the fuel cap. The proof came after noting that the problem completely went away when that cap was replaced. I have yet to see any traces of problems associated with my on-site fuel: tank is 150 gallons and I refill once a year, so fuel can hang out for quite a while.