Just a couple ?s

[Brandon8821]

Ok guys i have a 91 xlt 2.3 5 speed and theres a couple things im tring to figure out about it 1 thing is that at around 70 i get a vibration but i noticed yesturday that kts not as bad while haulin a load ive heard that it may be the universal ?

Also im trying to figure out what fuel additive would be the best to try and increase my milage as i drive about 45 mins one way to work all highway?

 

[Charles Sifers]

I'd definitely check the u-joint.
As for fuel additives...save your money.
None of them will give you better mileage.
Instead, do a tune-up with Motorcraft wires, plugs (gapped properly), and any other ignition parts that are due.
Use a NAPA Gold air filter and make sure you have the factory airbox. (No gauze filter or hot air intakes sold as cold air intakes)
Use full synthetic oil and a Motorcraft filter (Wix is your 2nd option).
Use synthetic lube in the gearbox and rear differential.
Make sure all the sensors are working within range. That includes O2 sensors and catalytic converters.
Make sure the tires are inflated to the proper psi ( I use the chalk method).
After you've done that, you'll be getting the best mileage you can from the truck.