No, not in a modern car. This used to be the case 60 years ago, but not today. If you are running modern oils (especially synthetic) in a well-maintained car and you pull a rocker cover, you should see no sludge built up.
If you try to run a lightweight concoction through your motor, you are likely to mess up some seals, risk metal-on-metal contact due to reduced viscosity, or break some odd bit of something sludge (if there is any) loose to block an oil passage.
Some modern engines are really prone to sludge, even with 3,000 mile oil and filter changes. We had a Toyota Sienna van about 15 years ago that was notorious for sludge and huge battles between Toyota and owners. Toyota would invalidate warranties if you were 10 miles over the oil change interval requirement.
I really think Mobil 1 is king in terms of bang for your buck for modern cars, pickups and suv’s. There are synthetics as good as Mobil 1, but generally are quite a bit more expensive, and the synthetics in the same price range aren’t near the same quality. I wouldn’t use anything else.
Ahhhhh, back in the Havoline 30W days.
We opened up an old man’s engine that had been on Havoline its whole 30,000 mile life and she was tarred up so bad had to scrape it out.
These days with quality oils, especially synthetics, no sludge.