I've tried some Lucas products and to be honest, I wasn't satisfied. Don't get me wrong, I wasn't expecting much of a change; Guess that was a good thing since I couldn't tell any difference. Yes, that is very un-scientific.
I have had some good results with Gunk/Solder Seal (Radiator Specialty) products. Plus they are HQ'ed in Charlotte, NC and I like doing business locally when I can. It is getting harder to find their products these days, especially since the last independent parts store in my county has closed. I used to order some of their products a case at a time and it would come in on the regular order at a great price.