Toyota put a new 2.5 I4 engine in the 2009 RAV4 (Toyota). It calls for either 5W-20 or 0W-20.
Toyota states both are fine, but they don't recommend switching back and forth. Use one and stick with it.
Does one give any better protection?
Any full synthetic 0w or 5w 20wt oil is what I would use.
The full synth's will flow better and pump easier when cold. And just in case you're low on oil, in the middle of the desert, stuck in traffic, the full synth should give you some peace of mind since it'll tolerate the higher temps better.
With some 5w30 and 0w30 full synth oils shearing into a 20wt anyway, I wouldn't rule them out either.
I always use full synthetic in my vehicles.
Since I've only used 5W-30 in my previous/other current vehicles, I just wasn't sure about which to choose (0W-20 or 5W-20). I can't imagine that I could even measure the difference in gas mileage.
I will be using Mobil 1.