Bought the truck used with 87K mi on it,and aside from the K&N air filter,it's stock.Best mileage I've seen with it has been around 15mpg highway.Now,with Hercules Terra Trac tires all around,using 15W40 weight oil,I'll get between 8 and 12 mpg.It uses no oil,with 112K mi on it.Exhaust manifolds were changed out by me,and it's got 2 3/4" single exhaust.
I'm wondering if a performance exhaust system will improve mileage any.As a curiosity,the check engine light flashes on and off,despite my having changed out the O2,EGR,throttle position,and MAP sensors.Emission codes indicate EGR sensor values out of limit,which I've been told happen from carboned up EGR valves..although I've changed out the EEGR valveand IAC valve.
I suspect the aggressive tread Terra Tracs,as a prime reason for my poor mileage.
Is anybody getting 15+mpg with is truck?