98 Burban plug wires and MPG

I have a 98 GMC Suburban, 86,000 miles with what I suspect are OEM plug wires. I get 18 MPG at 55/65 mph on 200 mile trips; freeway and divided highway with a few stop and gos and very easy on the acceleration pedel.
Same trip usually gets me 26 mpg on a 2001, V6 S10.
Bought the burban 2k miles ago and have flushed transmission and radiator and new plugs. I was expecting not more than 15 mpg but seeing 18 mpg is a bonus for this large vehicle.
Would new wires and new rotor do anything? Any other ideas on improving mpg short of driving 50 mph. Does premium deliver better MPG with this 350 engine?
hardworking
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High test is useless here. You could scan it and see if the O2 sensors are at their peak performance, Seems pretty good mileage right now, for that truck

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If the wires are breaking down and have increased resistance over new wires....then yes, a new set will help. Same with the plugs...if they are worn out. Any ignition improvements you make will increase the efiiciency of the engine by more complete combustion of the air/fuel mixture. most factory wires and plugs are of the resistance type which helps eliminate RFI (radio frequency interference), switching to low resistance (copper core) wires and non-resistor plugs will increase fire at the plug over a stock setup but you may also suffer noise on your stereo. Everything's a compromise my friend, gains in one area = losses in another.
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Mad-Dog
'79 Chevy K-10
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