As a new member of this WebSite, I had recently went through the troubles of the MOBIL 1 0W-20 search (after using the MOBIL 1 0W-20 for 3 years, and changing it at the conventional oil rate)(I'm keeping this Insight, as long as I can !!!).
The Honda Insight Operators Manual does specify that 5W-20 is fine. But, I did write (email) to MOBIL 1. Below is their response:
"Mobil Product Information mobilproducts@ourdataworks.com
It has been replaced by the 5W20 motor oil due to lack of demand
however, it will be relaunched in the retail market by 2nd qtr. of 2006"