There's been a lot of testing of oil additives including Lucas that will make you believe and show you that oil additives are just a placebo and can harm instead of protect.Good oils DO NOT need their formula doctored on.Good friend of mine had a 03 2500 that developed a rough idle,stall at times.Had a bad FCA.He could pour fuel additives in it including Marvel Mystery oil and it would run correct for that tank of fuel.The ONLY additive that DID NOT have a affect on the sticking FCA was Lucas fuel additive even with a whole large bottle added to the tank.The OTHERS he poured in he used about what was listed as a normal treatment.I have seen these trucks with anywhere from 150k to 500 plus k with NOTHING used in the fuel or oil and no injector or pump/engine repairs.