The Biggest Increase In Gas Mileage

The truck all packed for the return trip home to Alberta.

Because I have to do a lot of driving in my 91 Dodge 1500, my gas mileage is a going concern. I initially got only 9mpg when I purchased this truck. I never took the "check engine light" seriously, and still haven't put the light bulb back in its socket tucked behind the dash. 1991 truck computer readers are pre standard and so they cost a lot more, are make and year specific. With a lot of research I figured the oxygen sensor was probably malfunctioning, and an oxygen sensor ultimately cost less than a computer reader for the truck. The truck had 280,000 km, or 174,000 miles on it. From what I read Oxygen sensors only last for 200,000km at best, and then very poor mileage results from the worn out oxygen sensor.

I feared changing the Oxygen Sensor, as it is in the exhaust manifold, and I have broken many bolts holding exhaust pieces together. The heat it produces accelerates rust and corrosion. I procrastinated for months and then purchased the special "Oxygen Sensor Socket" on sale at Princess Auto. I am so glad I got this socket before I attempted the Oxygen Sensor change, but I still procrastinated another couple of weeks before I changed the sensor.

The final kick in the pants was a 2400+ km road trip to Victoria, which would make a great mileage test. So I got the sensor changed last minute, filled up the 240 liter fuel tank, and off to Victoria. I usually run out of fuel in that tank after 800km, and then run on the smaller 150 liter tank until I can get to a station. No surprise, on this road trip I didn't run my big tank out at 800km. To my surprise, the new oxygen sensor, and all the other mods I did got me just short of 1700km before I ran out of fuel. That is close enough to 20mpg for me, which was my ultimate goal. As it turns out part of that great mileage was my non stop driving for 12 hours, with virtually no traffic lights, and the motor never got to cool down or even stop. After that trip I got a consistent 12-13mpg, which is still a huge improvement on 9mpg. But there is lots I can still do.