For me it started the day I bought a new off the lot 1983 GMC 2500 4X4 with a (want a be diesel) the 6. 2 with the muncie 465 4 spd transmission. Not long after that purchase (a few years) the diesel fuel sulfur content here in California was lowered. Injection pumps were dying left and right on both the 6. 2's and ford's 6. 9's. Getting worried I took the advice an old diesel mechanic I trusted(the main motor man for diesels at the Geysers power plant) where I work. He told me to put 8oz's ATF to each 10 gallons diesel. "That'll keep'er lubed", he says. I kept up that practice and owned the truck until 2001 when I sold it with 322,000 miles on it. I did change to marvel mystery oil and redline later. I had to change out the injection pump twice and one set of injectors. Not because of failure but because they got tired after running so long. When I saw the cummins engine come out in the Dodge around 1989, I drooled, and dreamed until I could own one myself. July 2001 my dream came true. I drove home my new off the lot SLT 2001 high output with NV5600 six speed. I started adding marvel mystery oil with the first fill up and continue that practice. Then I got turned on to TDR by a coworker and subscribed. Been reading and learning since. Soon after I brought my new Dodge cummins home, my wife drove my dodge and fell in love with it. I was informed by my queen that it (my dodge-cummins) is now hers for family use and I get her ford F150 with 300 six cylinder with the 5sp. I just couldn't live like that for ever. So I did the next best thing, I groveled and negotiated for a few years then took the queen to Sacramento and bought her a 2005 dodge-cummins dually in her favorite color and all the bells and whistles. She promptly relinquished my 2001 back to me. I have been adding marvel mystery oil, and it has worked for me. Walmart has the best price around here for it. I live and work and play in the mountains, I pull a big tex dump trailer usually load with a combined weight of 23000 pounds. My 2001 has never failed me and has just turned 74000. I believe the fuel delivery system of the our diesel trucks will not complain if a reasonable amount of lubricity additive is added, and each cummins owner should stick with what works for them. What is certain is that the sulfur content in diesel fuel which acts as a lubricator is being decreased by the oil refiners to meet specs, and may continue to happen until removed completely. Sorry for the Novel- hope this helps. Vinny