There IS certainly truth to it if you believe strict test data. If low lube in a fuel shortens the life of one of your injection pumps by 20% or 30% - I doubt you'd ever know the difference. There has been a lot of testing and it boils down to this. I'm going to stick to the number used when testing for wear-scars of internal metal parts. This is usually the HFFR test ISO 12156. Mechancial fuel injection systems with fuel-lubricated injection pumps need a fuel that tests at less than "400,000" to last as designed. The average high-sulfur diesel was tested at 396,400 with the HFRR test at 60 degrees C. The average ULSD diesel tests at 666,650 which absolutely WILL make pumps wear prematurely. Now - ULSD is supposed to have lube additives put in to bring it up to around 500,000. So, as it stands - if everyone does the job right - and the additives get put in by everyone as they should - then it should be just barely adequate for older rotary pumps.
In short - diesel naturally had the lube qualities the old systems need - and now it does not and needs additives. Personally, I'm not that trusting all of this done properly, i.e. monitored and enforced since it's all still relatively new. I see putting lube back in the ULSD as a cheap investment. I use two-stroke oil added at a 200 to 1 ratio and it's been tested to bring the wear-scar # down by 160 microns -which is a lot. It adds more lube for less money then most commerical additives - but the two-stroke oil is not 2007 and newer emission's compliant.
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