Oil Extreme Better Than Synthetic in my Vette

I recently had Oil Extreme Better Than Synthetic motor oil put in my Vette.  The mobile oil change guy told me I could extend my drain interval two or three times safely.  I haven't reached that mileage yet but the car ran faster, cooler and quieter right away.  My gas mileage even went up.  I don't know exactly how much yet but I think it will be about an extra 50 miles on a tank.  Is there any problem with extending my drain interval this much?

I'm going to take it to the drag strip and see if my quarter mile speed went up.  If anyone has had experience with this product I would like to hear your comments.   Bill