Oatmeal Cream Stout Lactose?

So one of my mentor's uses Non-fat dried milk instead of Lactose for his oatmeal cream stout but I heard it can kill head retention. Has anyone used this substitute? I plan on brewing tomorrow.

I've not tried this. I'm curious why your mentor prefers the non-fat dry milk product over lactose?

Regarding head retention, it's my understanding that although the product states it is non-fat, there is still some fat content (about 1-1.25% of the product) in dry non-fat milk which could affect head retention.

Sources: http://www.innovatewithdairy.com/SiteCollectionDocuments/NDM_Spec.pdf and http://organicvalley.custhelp.com/cgi-bin/organicvalley.cfg/php/enduser/std_adp.php?p_faqid=214

He has been doing this for over 20 yrs and it's just cheaper and thinks it gives the same results and much cheaper.

I just bought a pound of lactose for $3 or $4 for a sweet stout I have in the fermenter. I don't know the cost of the dry milk, but I can't imagine it being too much cheaper. Also, lactose isn't the same thing as dry milk. Lactose is a sugar derived from milk and dry is literally milk that has been evaporated then dried into a powder.

I've never done a side by side comparison of non-fat dry milk vs. lactose in the same recipe to compare. I'm not saying your mentor is wrong, but in general, I tend to be wary of different things that I hear people say that "you can do" in brewing. Sure, there are a lot of ways to do things, but not all of them are the best way if you're trying to make great beer (I'm not saying that's the case here, just sayin )

If you decide to give the dry milk a shot, please post your results, I'd be curious to know how it comes out.