Poor Gas Mileage,Locking Hubs B4000

Just looking at the front axle on the 2003 4Ltr Mazda B4000 4X4 Standard, and wondering if putting locking hubs on it would improve the horrendous gas mileage for these vehicles.

Years ago I did that on my Jeep Wagoneer because it was designed to free wheel the front drive train up to the T Case. I installed the hubs and the gas guzzling went down quite a bit.

Thanks

What mileage are you getting, and what do you think it should get?
Is it a stock truck, or modified?

I know there's AVM hubs for 98-01 Rangers, but I don't know if they go up to '03 or not...