rim and tire size change

[Stump Jumper]

I realize that this question may be very basic and below you guys, but...I have an opportunity and am having trouble deciding. Have a 1988 Toy Pickup with stock rims (14 inch) and I have some 15 rims with nearly new tires available. Should I change to the 15's...is there any real advantage with basic street driving? Will it hurt my power and mileage considering it is just a 4 cyl.? Thanks!

 

[4RNNR]

you may have figured this out already, but what are the specific tire sizes ?

14" are:

15" are:

??