I was buying oil for my wife's scion yesterday and I saw 0w-30 for 10w-30 engines to improve gas mileage. Anyone use this?

I usually just look for 10w instantly and never noticed a 0w.

As I changed my wife's oil too, I noticed the cap listed 5w-20 or 0w-20 for the same economy improvement.

I've heard of 10w-30 engines going to 5w-20 to improve economy so I wonder how that compares to 0w-30...

 

I put the 0W30 in my wife's jetta since I used it to drive to work everyday. i haven't noticed any increase in economy. I do check mileage everytime I fill up also.