I agree with Woody. Synthetic works better! I use synthetic motor oil and transmission oil and get easy winter starts and good hot weather lubrication. Gas mileage improves somewhat and as gas prices now climb above one US $ a litre (approx quart) here in Sweden any improvement feels worth while.
I don´t know US prices, but here synt motor oil can cost anything between 11 and 48 US$ for the four litres (approx 4 quarts) needed. It pays to shop around and to buy when there are special prices. All brands I have seen meet Toyota´s specs, but if you are in doubt check the text on the bottle with your RAV´s Owner´s Manual.