GPM,LWT and EWT correlation?

My system requires 1.5 to 2 GPM per ton. Will more GPM mean more or less efficiency this winter? I can adjust the flow up to 16 GPM but is this helpful or less efficient? How much difference should I see between EWT and LWT? Is 7 degrees a good working number?
System is WF Envision 049 4 ton water to air in open loop using my existing well. Location is in RI.

Thanks in advance,

 

Increasing GPM above the recommended flow does nothing to add to efficiency.

A 5 - 10° delta T between EWT and LWT is what we shoot for.

 

Depending on well pump power and efficiency, it may be MORE efficient to have lower GPM per ton.

 

An eroded coax can be an unfortunate off-shoot of extremely high GPM.
J