I've been using my current set up for about 18 months, and I am without fail 73-77% efficiency, which I'm fine with. I also typically mash in around 1.4 qts/pound grain and sparge with .5 gallons/pound or until i get required volume.
Today I did a little session brew that was just 6.75 pounds (6 2 row .75 dextrin). I mashed in with almost 3 gallons and sparged with 5 gallons and collect 6.25. My efficiency was 88%. Anybody have experience with a much thinner mash leading to greater efficiency?
**edit** grains were crushed from same LHBS as always.
**edit v.2** Dang, there's a thread right below me on this. oops
Fermenting: Cherry Stout
On Tap: Town Hall Hope & King Scotch Ale, Red Hook ESB
Conversion eff. will go up to a point, but you will lose lauter eff. Thinner mashes facilitate more enzyme activity, but this increase in mash water steals from your sparge water. Here is a little explaination.