RAY: Here's the answer. Putting 20W-50 into the oil crankcase won't necessarily slow down your oil consumption if it's getting by the rings, because there are three rings in every piston, and the bottom ring -- called the oil control ring -- is supposed to scrape the oil off the cylinder as each piston descends.
Now, if the oil scraper ring isn't working, that oil won't get scraped off. Instead, there'll be a thicker film of oil on the cylinder wall. And, the engine will burn up that oil as it would the thinner viscosity. In fact, it'll burn it up faster, because the film is thicker.
TOM: It's twice as dense as the lighter oil.
RAY: Exactly. And Butch is twice as dense, too. That's why sometimes using heavier oil, although, intuitively it seems like it should reduce your consumption, will in fact increase the consumption because it's leaving a thicker film on the cylinder walls.
Instead, it comes out the tail pipe as pretty, billowy blue clouds.
TOM: It is kind of pretty, isn't it? Especially when it's sunset and the sun is coming down through those clouds into your cloud of blue smoke. I think it's rather nice --
RAY: Poetic, actually.
TOM: You don't see that anymore.
RAY: Thank God!
[ Car Talk Puzzler ]