Ditto what jaotguy said. Ok as temporary fix until you can fix it right. I've used Lucas products for many years. What I've found is; the fuel treatment is pretty good at cleaning injectors (both gas and diesel) and fighting water problems associated with ethanol fuels. However, on gas engines, you'll see your fuel treatment again on your fouled spark plugs. (it's the light brown powdery-looking gunk)
The oil stabilizer helps oil stick to the parts to help prevent metal/metal contact, but in the near future you'll see it again when you finally tear down the engine because of a main or rod bearing failure. (it will be in the form of 'tar' blocking the oil passages that feed oil to the bearings you're trying to protect)
Not trying to knock anybody's products, they pretty much work as advertised but are a short term fix.
My personal rule of thumb is this; when you need to use this kind of product (any brand, not just Lucas), it's time to start thinking about trading in, selling, or planning for the upcoming rebuild. Happy motoring.
A long running Generator thread on here has given me reason to think that you can get some pretty big differences between what happens with similar equipment, just due to regional fuel variations.
We inherited a car from my MIL's estate. My FIL thought he had changed the plugs not long before we got it. We put about 40,000 km on it, before I took a look at the plugs - no, they'd been in car a lot longer than he thought. From the time we got it, I've used Lucas fuel treatment on that car, partly because it gains me about 0.5 L/100km on today's fuel. The NGK plugs I took out were very worn (to the point that the V groove was gone), but were spotlessly clean. At least 80% of our driving is highway, so that can be a factor too.
Other than the recent product I started the thread on, I have no direct experience with their motor oil treatments.
Rgds, D.