I saw a test on this and i noticed one thing that some people skipped over, that was the fact that the diesel used was before the lubricity treatment that the oil companies do themselves. The Lucas did improve the lubricity of the "dry" diesel, but it wasn't a very significant improvement. The treatments from the companies themselves do a better job, but Lucas on top of the add in's would help some IMO. (doesn't seem like alot though).Before adding a bunch of additives to your oil, why not buy a better oil? What are you currently using?
As for fuel additives, Stanadyne, AMSOIL, Opti-lube among others are all good. Lucas didn't fare well in the lab tests they ran a few yrs ago. It was proven then that you got more lubricity from straight diesel than by adding lucas fuel additives.