Last tankful gave me 12.53 mpg... a new record low. Are they sneaking more ethanol in the gas these days?

Truck is running perfect. New plugs, valve springs, lifters, stem seals and fresh oil... 0W-20 full syn. I thought my mileage would improve, but it seems to have gotten worse. Tires are 33 PSI.

work from home (covid perk) and almost all the mileage is local short trips, running errands and what not. I was getting better mileage when driving an hour each way in heavy traffic. Now I'm almost never on the highway.

This is the 4.7L with 314K mi on it. Maybe it's time I finally replace these O2 sensors? Either that, or I gotta stop idling so long in the Popeyes and Dunkin Donuts drive thrus. Gotta have that DD coffee though. LOL

What are you guys getting?

 

That makes sense if it's all city driving. I don't know what the overzealous EPA rating was, but 15/19 sounds familiar, and those are usually +2 to the happy side. So 13/17 would not be unexpected.

 

A sudden unexplained drop in mileage usually means the O2s have gone bad, and Bosch will make it even worse. New ones may bring you back up to where you were. And, have you ever considered just making the coffee at home?



Or, you can switch to this, which tastes a lot better.


And, a bit of interesting reading for you - Dunkin and Folgers, both made by Smuckers. Wonder if they're not made on the same line, with the same machines and the same beans?
https://www.businessinsider.com/r-sm...rs-back-2015-7

 

I was getting roughly 13.5 - 14 before this last tank, so the drop is not huge but I thought with all the work it would've gone the other way. I've never had a peep out of the O2 sensors but I guess they must be dulled in performance by now. Thanks for the coffee tips. I don't have a machine because of the temptation. I limit myself to one a day, see.

 

sheeeeeeet if you're averaging 13.5-14 mixed, I'm surprised you're getting as good as 12.5 city-only.

 

Your problem is just all the city driving and air conditioning.
my mileage dumps around the city too.

​I make my own coffee sometimes, but for some reason it always tastes better when Dunkin makes it for me ☕

Drive to a Dunkin 50 miles away tomorrow and your mileage will magically go up ⛽

 

Yeah, I kinda forgot about the AC. It's been over a month since I've driven any decent miles on the highway and even then, it was few and far between. I guess I've never driven the truck strictly locally this much and combined with the summer heat, I can see your point. I'm still gonna research some O2 sensors, but that little voice tells me not to F with anything that ain't broke.

 

If you find a way to check your STFT and LTFT's, that will tell you if the O2's need replacement

 

I've always looked at O2 sensors as a maintenance item. But that's just me, I guess.

 

I was bored this evening, so I sprayed the shift linkage on the tranny with graphite dry lube. I do it once a year... it makes shifting at the stalk feel very smooth, esp shifting out of park, which is usually clunky.

While under there, I verified that the Dak only has two O2 senors. That's important when considering the fea$ability of replacement. I'd never recover the $$$ spent on 4 sensors in improved gas mileage. I shoulda sprayed them with PB blaster but it slipped my mind. Not too bad though. No real rust here in the south. Looks like a regular or adjustable wrench should do the job just fine. No crows foot or special O2 socket needed


Upstream sensor (before the cat). It's gonna be a beyoch unplugging this one as the plug is jammed between the body heat shield and the transmission.







Downstream Sensor (past the cat). The camera was pointing towards the front of the truck here.