What brand of Mos2 did you use Lubro Moly ?, I tried it (Lubro Moly ) and I didn't notice any differences to be fair I didn't leave it in that long. Also how much did you use ?
I used the liqui-moly brand. You have to leave it in for the whole interval. It takes time to plate the metal surfaces and needs heat and pressure to work.
In my experience with mos2 fuel economy was unaffected until the 3rd tank of fuel. I keep track of mileage of every tank of fuel in all of my vehicles. My mustang and truck both saw a mileage increase of 1km per liter of fuel averaged over the entire tank.
I've got multiple iPhone apps to calculate mileage. I always calculate it on fuel put in against kms driven.
While driving to BC I got 650kms from a single tank of fuel all highway in the truck. Average was always 450 with mixed city/highway.
It is noticeable when I don't use the mos2. If I use it,then run out the interval,then new oil with no mos2 fuel mileage gradually declines back to 450 a tank by the end of the untreated oils change interval. It works well enough that everytime I see it I buy it because it's very hard to find.