Ahhh, the perenial FE issue: Tire pressure.

And as you accurately describe, improperly inflated winter tires can have a very nasty impact not just on handling and safety but also on fuel economy. Also to note is that most winter tires have a much higher maximum pressure than All Season tires do - especially the LRR Dunlops we all have.

So, we have to distinguish between the two sets of tires. As you mentioned, 51 psi is a good value for most winter tires.

Cheers;

MSantos