it does work... on some vehicles. it won't give you 20% more mpg tho.
I haven't used it yet on the ctd, but I did try it in my gasser. it added about 1. 5 mpg on the highway, and didn't really seem to help much in the city. This is in a car that gets 27-28 on the highway w/o acetone.
the ratio is no more than 3 oz per 10 gals.
it is less for diesel, but not sure how much less.