I've been having a lot of problems with my mash efficiency since I started brewing AG in May. At first I chalked it up to inexperience but after this many months and brews under my belt it has become very frustrating. I've only started measuring the pre-boil gravity for my last four batches but my OG have always been 3-7 points low. Mind you 3 points is not a huge deal, but my pre boil gravities are consistently 20-24 points low! So I usually crank the heat on the propane to boil off as much as possible so that my OG lands somewhere close to where it needs to be. Generally it's 7 points low, I've only come within 3 points once. Anyway, I know I get close to my expected OG in the end but I'm losing more wort than I should be boiling this way. So I'm obviously doing something very wrong but have no idea what. I generally come within a degree or two of hitting my mash temp.
I've read countless articles online about mash efficiency and even a book or two and tried everything I can find to get my pre boil gravity up but with no luck at all. Here's what I've tried so far.
-I bought a new hydrometer (long shot I know but this made no difference)
-Measured the sparge and strike water temperature with an external thermometer as well as the kettle thermometer to make sure they are consistent (they are)
-Narrowed the gap in my BC to 0.34
-Tried a very slow batch sparge (45-60 minutes, no improvement)
This evening I brewed a chocolate espresso oatmeal stout. I hit my mash temperature (156) perfectly. I let it rest for 60 minutes and measured the temperature at the end of the mash. I had only lost 0.6C over the hour. I then sparged over about 15 minutes and added the strike water at 170. I let that sit for about another 10 minutes before finishing the sparge and getting to my pre boil volume. I gave the wort a gentle stir to ensure both runnings were mixed well and measured the SG. It was 22 points low!
At this point I am incredibly frustrated!
I have run out of ideas to try to boost my efficiency. I'm hoping someone here can suggest anything for me to try. I'm open to any ideas, anything at all.