Just about every vehicle I've owned has gone well past 200K, sans additives. This 03' Dak of mine, had nearly 250K when I bought it recently. The owner didn't use additives either. Modern day engine oil already comes with the best additives you'll need. You just need to make sure you keep enough of it in the engine to "act as microscopic ball bearings between every contact surface" and keep to the OCI. Furthermore, you may be negatively affecting the native additive package with your addition.

Lead was never "a lubricant in gas". It was added because it boosted octane and prevented knocking, period. That is, until it started poisoning people, so hopefully you are not spilling any on your skin if you do your own oil changes.

Don't think engine oil contents won't affect the CAT, especially when the engine gets up in age. Remember those things called piston rings and valves?

Hate to go Wiki on you, but here is the similarity to slick 50....

http://en.wikipedia.org/wiki/Catalytic_converter

Damage

Catalyst poisoning occurs when the catalytic converter is exposed to exhaust containing substances that coat the working surfaces, encapsulating the catalyst so that it cannot contact and treat the exhaust. The most-notable contaminant is lead, so vehicles equipped with catalytic converters can be run only on unleaded fuels. Other common catalyst poisons include fuel sulfur, manganese (originating primarily from the gasoline additive MMT), and silicone, which can enter the exhaust stream if the engine has a leak that allows coolant into the combustion chamber. Phosphorus is another catalyst contaminant. Although phosphorus is no longer used in gasoline, it (and zinc, another low-level catalyst contaminant) was until recently widely used in engine oil antiwear additives such as zinc dithiophosphate (ZDDP). Beginning in 2006, a reduction of phosphorus concentration in engine oils was mandated.

 

I run Lucas Oil Stabilizer in everything I own. We use it in the dirt track cars too and engines look brand new inside at the end of the season. Takes 3 guys to pull the crank...not for weight, to slippery for one guy to handle

 

I used to use oil treatment with every change, weather it worked or not I don't know. For the past 3 changes, I've used Royal Purple Synthetic 05/30. I don't know if it's my imagination but truck seems to really run better. Down side is the Purple runs $10.00/qt!

 

I've used Lucas Oil Treatment in several work vans....Chevy Astros with 4.6 V-6. All three vans had over 350,000 miles on them when they were "retired". My 98 Dakota has 110,000 on it and I'm considering the Lucas again for that. Keep in mind, I only used about 1/3 of the bottle at oil changes every 5,000 miles.