I've been following this and other similar threads with great interest as I've had the honour?? of being directly involved with troubleshooting, root cause analysis and laboratory analysis of injectrs and causes of injector failures. I can write a book on findings and causes but herewith a short-ish writeup of my findings and deductions.
Earthmoving technology is probably a short leg behind F1 - believe it or not. We had similar problems starting in the early 90's and still have some issues with the latest extreme high pressure multi-injection map injectors.
Fact - Diesel fuel-from-Coal also have, by nature, a much higher percentage of very small but extremely abrasive particles than crude-derived diesel.
Most injector problems really started when we moved from PC engines (1520 to 1750Psi) to DI (2200 to 2500Psi), and then from the early 2200Psi pencil-typedirect injectors to unit injectors (9000Psi), later hydraulically-activated electronically controlled unit injectors (25000Psi), and of late even higher pressure multi-injection unit injectors (up to 35000Psi).
I've had the opportunity to research injector problems - analysis mostly indicated 3 very distinct causes.
Water - this causes vapor expansion erosion (water expands very rapidly when placed under extreme prssure such as in the injector tip). This can cause corrosion on the seat and ports, it can cause wear on the ports and if enough water, will pop the tips off the injectors causing severe engine damage. Prevent this with a high quality drainable water trap.
Lubricity. This used to be a huge problem during the early Sasol years but have been largely resolved. It does become more of a problem at the Reef during winter as the fuel companies add a higher percentage parrafin to the diesel fuel to help fight the waxing of the fuel during storage and use. I believe most fuel companies have now sorted the pure lubricity related issues - however, 4ePajero's suggestion of 2-stroke oil with the fuel is and remains a good one and will do no damage whilst offering protection when the fuel company gets it wrong...
Dirt - the biggest killer at present. Dirt has two distinct results - one which cannot be "healed" without injector replacement and one which can be "healed". Then first result is worn seats and ports which results in poor spray patterns, incorrect pressures, in turn leading to hard starting, smoking, increased fuel consumption, cylinder washing (and possible seizure if not attended to). To fix this the injector tip (or complete injector on some makes) needs to be replaced.
The second phenomina, which very few manufacturers even knows about, nevermind paying attention to, was, to my knowledge, first sighted and identified by a dear old German friend of mine, an ex-director of a well known earthmoving Co. and later a pioneer of depth-filtration in SA and overseas. He called the phenomina "injector needle stiction" and went on to prove that firstly it does exist, that it is caused by both size and quantity of dirt in fuel and that the results can be catastrophic. The dirt size issue is self explanitory I believe? - the second issue is one where multitudes of small particles tend to bunch and conglomorate together resulting in even bigger damage - simply because they pass through all current filters and can form totally undetected.
The conglomerated dirt causes injector needle stiction which causes injector precision disruption through delays caused by drag between the injector needle and bore - resulting in erratic movement of the needle resulting in incorrect timing, incorrect amounts of fuel injected (starting actual injection late and continuing past the required cut-off point), overfuelling, etc. Most of all though - it causes all of this virtually undetected and is the cause of many modern diesel maladies.
The good news is that provided the needle seat and ports are still in good nick, the effects of stiction can be reversed by using super clean fuel. In short, the "stiction" diminishes and eventually goes away completely, leaving behind a fully, properly functioning injector.
2-stroke oil will help with general lubricity but cannot completely prevent the stiction caused by debris and dirt in the fuel. This is the reason for calling for the min-3micron series filtration - not only to filter down to 3micron or less, but to remove as much of that sized particles as possible.
The single biggest preventor of wear and failures is thus 1)water removal 2)Fine filtration (3micron absolute or less, and lately 2micron series filtration which is basically 2 x 2micron filters placed in series with a 5 micron filter as pre-filter)
