When I bought my raider it had 333K miles on it, got 10mpg. New-to-me Mikuni carb with secondaries working, 12mpg. New gas cap and a new vacuum hose going to the brake booster: 15mpg. Following a semi for over 100 miles at 55mph with all my belongings in the back :19mpg.

I once went from 17mpg around town to 21mpg around town in a ford taurus just by easing off the gas and driving more smoothly.

My suggestion to you: Put a valve spring under your accelerator :p

First off... l I'd ditch the Lucas. Oil viscosity effects mpg. Hence ford secs 5w20 in their 4.6 here but in and there's countries they call for 10w40. Lucas doesn't really do anything great. Want to maximize your mpg through oil... run a decent synthetic. Mobil 1 can be had on sale for 35$.

I wouldn't dare put that stuff in your diffs. Its not gl5 rated. It's not capable of handling the high shock of of direct contact gears. A lot of what lucas says isnt verified or true. See bobistheoilguy.com for the facts.

Maybe simple maintenance... change all your fluids and filters, a quick check of your alignment (tape measure will do), check air in tires, quick clean of the air flow meter is applicable, and check the drive line for resistance (wheel bearing play, drive shaft u joints...)

with my land cruiser i had Scanguage and it really did help. it changes your driving style when you look down and see your currently getting 3 mpg because your trying to haul ass up hill. btw i hear you guys are getting killed with snow in Michigan, I'm heading that way tomorrow to go see my parents.

well we have here about 38in on the ground the snow banks by my house are taller then the montero.

So Can the Lucas oil additive get some 5w-20 ??? can that run all right in the 3,0?

Make sure your maintenance is up to date - air filter, etc. Run the thinnest recommended oil and use synthetic - differentials also. Manual locking hubs will reduce the amount of drivetrain that you're turning while driving. Take any and all unnecessary weight out of the vehicle.

After all of that, adjusting your driving style is still the best way to get better mileage. If you're serious about wanting better mileage then lose the heavy foot and coast as much as possible.

I used the Ford motor as an example... not saying you should be using 0w20 or something. I'm not sure what your truck specs... 5w30? I'd stick with that, no lucas. If oil wasn't "stable" on its own, I believe companies like Mobile would have resolved that "issue" decades ago. I've only seen Lucas be of use in motors with blown rings. Even Blackstone Laboratories, one of the go to motor oil analysis labs, recommends not using it.