Originally posted by tvpierce
On a spark-ignition engine, would there be any advantage to running a CI-4 oil for a short duration to gain the advantage of the higher level of detergent additives?
Possibly. CI-4 oil might be able to free a "sticky lifter". Modern engines warm up quicker and meter fuel much more accurately than vintage carbureted engines, so modern SI engines don't need as much detergent, dispersant, anti-wear, and anti-corrosion additive as vintage SI engines. That's why I use CI-4 oil in my vintage cars.
The catalytic converter issue is why the level of additive in modern SI engine oils has actually been reduced over the years, and modern SI engines don't need as much additive.
If you have a modern SI engine with a converter and no sticky lifter issues I'd recommend sticking with SL oil. If you have a sticky lifter you could try a load of CI-4 and see if it helps. There are also oil supplements that have additives that are designed to free up sticky lifters.