Got a 91 F250 with the 351W about 140000 miles on it. The previous owner used 5w-30 synthetic blend oil with Lucas additives. When I go to change the oil should I stick with that or just go full synthetic?

Thanks
idcwby

 

Depends on the temp range where you drive, but if it runs well using that product and has accumulated all those miles without any problems, why change oil type now?

 

It'll get down to 0 in the winter months and during the summer it can reach 100. It runs good, just thinking that I may be able to get better mileage with synthetic.

Thanks
idcwby

 

Those year(s) vehicles were not known for great mileage. When taken care of though, they were very dependable. Watch the front brake pads on it because they provided no warning when it was time to replace them. As far as mileage, tire pressure, good maintenance and light foot on the throttle made the most difference. Good truck !