Any advice on efficiency

Hello again...I could use a bit of advice from my fellow homebrewers...I recently started progressing away from extract brewing to partial mashing (dominant amount of base grain (2 row and Marris) and very light on the XLDME)...I have a 5gal IGLOO dispenser with a 7.5g brew pot with a propane burner)...My process is thru Beersmith and using the 3 batch sparge method...I mash in with specified amount and Temp stays constant +/- couple of degrees (158)...Vorlauf off 1-1.5qts...Sparge off in three batches in the amount specified, which i have set up inside on stove (sparge 1/sparge2/sparge 3)...Full boil for 90min...Hop schedule as specified along with adjuncts (Irish Moss/Lactose etc)...Cool to 65 (ice bath)...Strain into primary...aerate via agitation...Wait RDWHAHB...Problem is this...I have hit my OG per recipe but after 10-14 days my FG is off by 4-5 points..I have done a Magic Hat and Dead Guy clone (no PACMAN for the DG )...and just finished brewing a Milk Stout...Is this an attenuation issue or an effciency issue and what can I do to fix this...Beers taste great but am I missing something? Underpitching? or should I even be concerned? Thanks

OG is an efficiency issue and FG is an attenuation issue. Are you hitting your OG? If so, I would look more into the attenuation issue

Yep im hitting my OG pretty much dead on...

ok so then look at pitch rate...are you using starters with your liquid yeast? are you hitting your ideal fermentation temps? Aeration is rarely the reason for consistent poor attenuation....

Correct. Efficiency is how much sugar you are extracting from grain in a mash. Attenuation is how much of those sugars are being converted into alcohol by the yeast.

(OG-FG)/OG=% of attenuation. In other words. if you start with 1.050 and you finish with 1.010 that is 80% attenuation. With most American yeasts you should be able to get 75%. I don't think that 5 points is all that much though. Your hyrdometer could be off. You probably couldn't taste much difference. if you were 10 points off then i'd start to worry.

If you are having issues getting your FG low enough then I'd suggest using the pitching rate calculator http://www.mrmalty.com/calc/calc.html to make sure you are pitching the correct amount of yeast.

I would look at your 158 mash temp, maybe try 152 or so.

oh yeah; didn't notice that....158 is a pretty high mash temp...