Depending on how cold it gets where you live, the 5W-20 will work fine. As has been discussed previously, the difference between 0W-20 and 5W-20 is only going to be "noticable" on start up. Once the oil begins warming up, your engine won't know the difference between the 2. In VERY cold climates I would definitely want a 0W-20 synthetic. Since Mobil 1 is no longer available in 0W-20, I believe Penzoil is the only other manufacturer making a 0W-20 full synthetic. The Honda 0W-20, is NOT synthetic but perfectly accecptable if you want to stick with Honda's reccomended weight oil for the Insight. However, I suspect the cost of Honda's non-synthetic is probably only slightly less than a full synthetic. I last paid $4.29 Qt for Mobil 1 when it was available. Being that you will be using less than 3 Qts, it really shouldn't be a $$ issue, at least not for me.