[MP81]

crazy talk

yet to see a DIC pic of high mpg with high mph.

Our best tank ever of 57.4 was started just before we got back into Michigan (Ohio Turnpike) - as soon as we did, cruise was set up to 75 (and I went WOT to get there upon crossing the state line). We filled up about 100 miles later of a solid 75 mph on the highway (mixed with a couple miles of city), in ~40 degree temps, and got that.

Watching the instantaneous fuel economy - which was something I did the entire time I was driving down and back from NC - it really seemed to favor 70 mph vs 65 or 60 mph.

 

[beaurrr]

I noticed my fuel consumption increasing before I got the P0133 code. Then, after the dealer replaced the sensor and reset the fuel trim (and possibly updated the ecu) the fuel consumption dropped back to where I'd seen it when I first got the car two months ago. For me that means 30+ mpg around town.
I wonder about the sooting up of the O2 sensor as a cause of increased fuel consumption. Is it possible that a dirty sensor might cause a decrease in mileage without actually triggering a DTC?

 

[diesel]

I noticed my fuel consumption increasing before I got the P0133 code. Then, after the dealer replaced the sensor and reset the fuel trim (and possibly updated the ecu) the fuel consumption dropped back to where I'd seen it when I first got the car two months ago. For me that means 30+ mpg around town.
I wonder about the sooting up of the O2 sensor as a cause of increased fuel consumption. Is it possible that a dirty sensor might cause a decrease in mileage without actually triggering a DTC?

This is a good observation. I think you might be onto something there.

 

[BrightParrot]

OK - next test. On a relatively flat stretch of highway (rolling hills are ok as long as up and down are roughly equal) reset one of your trip odometers and watch the average MPG vs. average speed. Report distance, speed, and mpg numbers in both directions on this stretch of road please. What I'm looking for here is to see if your car is performing properly on the highway.

Sorry for the delay, but life sometimes gets in the way... here are the test results.
Test course – US 421 between Windy Gap and Yadkinville NC
Sunday, 10/2/16; 1:45 – 2:15 PM @81 degrees (A/C on for all tests)
Tire pressures: RF 42; LF 41; RR 42; LR 43

Cruise control set to 55 mph
RPM average 1500 – 1600
52.5 mpg @ 6 mi – 55.1 average speed

Cruise control set to 65 mph
RPM average 1800
46.0 mpg @ 5.4 miles - 65.4 average speed

Cruise control set to 70 mph
RPM average 2000
35.3 mpg @ 10.6 miles - 69.5 average speed
34.5 mpg @ 12 miles - 69.7 average speed (continued from above test)

No cruise control
42.3 mpg @ 6 miles - 68.9 average speed
40.9 mpg @ 7.2 miles - 66.1 average speed (continued from above test, includes going from US 421 to I-77)
36.5 mpg @ 6.3 miles - 73.2 average speed (Test on I-77 N)

Since the test, I've had a flat, (wore out the inside edge of the tire, but the alignment #s didn't show anything really out of whack... very strange.) got all new tires (Continental Pure Contacts), front end alignment, had the HVAC flashed to fix the hum issue and had the LTFT reset. We'll see if there is a difference. I also ran a tank of B18 through it before I got the flat as I wanted the detergent properties of the bio to make sure everything was "cleaned out" so to speak. Now I'm back on regular diesel from Sheetz. We'll see what happens...

 

[BrightParrot]

So after all of the above, I seem to be a bit happier at roughly 35 MPG per tank (using ACar app to record mileage / gallons for calculations) and that's with my 37 mile drive to work with the 2000 ft elevation change. Not bad. I'll be going from NC to CT after thanksgiving, we'll see what happens. I am looking forward to seeing what kind of mileage I get on that trip as I don't get to do a lot of highway driving. (My work ride is 45-55 MPH roads, so not terrible, but it's still no highway.)
I also just had the NOX sensor recall done, we'll have to see if that affects anything.

 

[diesel]

So after all of the above, I seem to be a bit happier at roughly 35 MPG per tank (using ACar app to record mileage / gallons for calculations) and that's with my 37 mile drive to work with the 2000 ft elevation change. Not bad. I'll be going from NC to CT after thanksgiving, we'll see what happens. I am looking forward to seeing what kind of mileage I get on that trip as I don't get to do a lot of highway driving. (My work ride is 45-55 MPH roads, so not terrible, but it's still no highway.)
I also just had the NOX sensor recall done, we'll have to see if that affects anything.

I would think that most of what you lose going up the 2000 ft change, you would gain back coming back down.

 

[BrightParrot]

I would think that most of what you lose going up the 2000 ft change, you would gain back coming back down.

I guess that depends on how hard I pass whatever log truck or tractor I encounter on the way up... :wavetowel2: