What's the pros and cons of low tension piston rings? And why they use'em alot in modern cars?
The reason they are used in modern cars is that it increases efficiency and gas mileage due to lower internal engine friction. Probably the main downside is that blowby is increased which places more demands on the crankcase ventilation system. Due to this some engines built this way, particularly early designs, have been prone to severe sludging resulting in engine failure.
Oh, i see!
is it related to oil consumption?
I suppose it could be since oil can be drawn into the intake through the PCV system. It's also possible more oil may get through the oil control rings especially as they wear. I wouldn't doubt that it's more difficult to control oil consumption with low-tension rings. (I'm not an engine designer though so these are just educated guesses.)
So generally what causes a brand new car to burn oil?
In the case of Toyota and Subaru it was defective piston rings when they had that problem a few years back. Defective parts, poor design, lack of quality control can all lead to oil burning in a new engine.
Aaaa, alright, thanks man
The molybendum steel used in modern rings (as opposed to old fashioned iron) take longer to seat into the cylinder walls. This is why when you get a new or rebuilt engine, they tell you to keep a close eye on your oil until the rings seat in.
Thanks man!