What's the acura rl oil type?

The oil types used on the 2008 Acura RL are 5W-20 and 0W-20. Those two oils can be used at all temperatures. I would recommend to use one or the other. If You want to know the capacity, then it iS4.5 US quarts with filter and 4.2 US quarts without a filter. What the engine oil does is lubricates Your motor and its part so that they will last a long time. It also cleans and conditions the gaskets it comes in contact with so that they don't dry out or crack. Make sure You're replacing the oil as scheduled so that You don't run the risk of getting gunky oil.