Well, the good thing about having such cruddy fuel economy to begin with is that it doesn't take much to improve it by 10% and offset gas prices rising 10%! If it's been a while since you've changed our the front o2 sensors that's where I would start looking for "free" fuel economy. O2 sensors read "lean" as they age causing the computer to inject more fuel than required. The computer won't throw a code until your long term fuel trim is over 10%. The front sensors are easy to change and honestly, if you get a reasonable bump in fuel economy it won't take long to offset the purchase price, especially if you drive your truck with any regularity or over distance.

Storytime: 2 years back I took my truck on a trip from Seattle to Montana and it threw a long term code just outside of Spokane- I spent the rest of the trip getting 8MPG, swapped out the front o2 sensors the moment I got home and codes went away and my MPG went back up to its normal 13-14. I wish I had the time/opportunity to get them swapped out in a shop along the way, even paying someone to do it I probably would have came out ahead for fuel cost, of course this was back at the start of COVID when gas prices were super low because no one was commuting.

 

Set of front O2 sensors will run you about $50 at rockauto. I didn't buy to improve fuel economy, but I did take deliver on a pair two days ago. A 10% bump in economy at my local fuel prices would pay for the sensors before you next oil change - 1800 miles by my math. It would save you about 2.7¢/mile. Even a 5% bump pays back in 3500 miles (1.5¢/mile).

Oh, and the above numbers assume your "bad" economy is 14 mpg. Fuelly says 13 for Disco 2 V8, so the return will be a bit faster.

Good call out!

 

I'm super tempted. I'd like to go south and get out of this cold weather.

I did this today:

 

there are a few members here that dont even run o2 sensors, i doubt you will get 10 % more fuel economy, ask extinct how many mpg he gets, he runs with no o2 lol

 

How do you (and why would you) not run upstream o2 sensors? They would seem to be a pretty crucial and imbedded part of the engine management system.

 

My 97 XD has no cats & rarely ever tosses a code for O2 sensors unless I am at idle for extended periods of time out on the trail. The 95 D1 with just 2 O2 sensors could care less and it's also running without cats. Crawl under either of them & nothing to steal from me!! Both D1's average 10-13mpg and only the 95 is running 93 octane fuel.

 

I have a 2000 with four dead 02's, been running it like that for two years, gets 17mpg consistently on stock size Michelins at 75 mph. ECU defaults to MAF fueling when the sensors are completely dead. I did a post a while back showing the data from my code reader. South African trucks had no cats because they had leaded fuel, no 02's. Not sure how but would be interesting flash that program in.

Unplug both front and rear 02's and see how it runs, runs just fine.

 

That's actually kind of fascinating. Does it throw codes/CEL with no sensors? It seems it would.

 

Yes of course it does. I ignore it. Shoemakers shoes...

 

So the lesson today is that, we don't really need the o2 sensors.

Headed down to the basement now to rip all mine out. Hoping it will make the truck lighter and get better gas mileage Kidding, but this is fascinating. I always thought they had to have them or otherwise they would run awful and stall the truck.