B737-400 Engine Anti Ice Usage
 

Hi!
Can anyone help me out here. SOP says use engine anti ice when visible moisture AND TAT 10oC below. Ok fine but lately there are so many pilots keeping it on until 13-14oC some even say as long as they THINK they need it especially on descend on idle power. The note by Boeing in our company Supp Proc cold wx ops say DO NOT use EAI when TAT is 10oC above, rather than NOT RECOMMENDED. So I guess there must be a good or proven reason for Boeing to print it in BOLD. Everyone is "enforcing" their own buffer/limit to this so sometimes I feel like telling them why not bring extra extra fuel for good weather. So, I suspect it has got something to do technically to the engine. Well, pls help me out guys!

Thanks!!