I was "playing" with my excel spread sheet of gas mileage data today and did some sorting of data by brands of gas used then some data crunching of brand of gas vs. average mpg to see if anything popped out. I had data doing back to 2008.

station....mpg
7-11.......28.4
BP..........30.2
Chevron..29.5
Hess.......32.1
Mobil......30.6
RaceTrac.28.8
Raceway.30.7
Sam's.....28.6
Sheetz....32.1
Shell.......28.6
Sunoco....33.7
Valero.....29.4
Xtra........31.5

I'm unsure what it all means, I do know that the Sheetz stations are up in Va and Pa so I only stop there when I'm on a road trip, so highway mileage.
The smallest subset of stations was the 7-11 and that was five fill-ups.

Sunoco was twelve fill-ups and the highest mpg and also may be stops when I was traveling.

BP was about sixty fill-ups and is local and highway (I have a BP credit card).

Shell is about 40 fill-ups and is also local driving.

There are some "off brands" of gas I have used (Sam's Club or Xtra) and I don't see significant mpg differences using them. Sam's gets used usually all local driving while Xtra is a station that had cheap prices when I was up at my brother's in upstate NY.

The Chevron station became a Valero a year or so back, but I get the same mpg from those pumps. (?)

I may resort the data by dates to see if I detect any variations between winter and summer blends, if they have different blends in Florida where I do most of my driving.

 

I'm chalking up my low mileage to the winter driving I'm doing at the moment - and the Polar Vortex, which caused me to have to get my car started regularly halfway through my shift.

 

Today I did an experiment. 300 miles round trip all but less than 5 miles at highway speed with cruise control, one tank of gas. Never reset AVG MPG except at fuel up in the first half mile, after 4 mile warmup. (drove 4 miles to gas station. Reset at fillup. drove less than .5 mile to interstate. drove 65 miles, stopped turned around. drove 150 miles, stopped turned around. drove 100 miles, 4 in light local traffic.)

First 150 miles ambient temp around 20F got 25 MPG, return trip ambient temp got up to 38F got 29MPG. So on the return trip actually got over 30MPG, if I'd have reset.

I guess the "brain" does something to the air/fuel mix at low temps.

 

Actually the ECM and O2 sensors would be leaning the air/fuel mixture out due to the "Winter Blend Fuel" now being sold this time of year with its added dose of MBTE and Butane oxygenators.

Oxygenators bring extra oxygen to the combustion event in liquid form that is released at time of combustions. For MTBE-laden fuel, a stoichiometric ratio can be as low as 14.1:1 instead of the more normal 14.7:1-15.0:1 which requires a leaning out of the mixture to avoid unacceptable combustion chamber temperatures once the vehicle is in Closed Loop Mode.

Chances are the variation in mileage can be more accurately be attributed to increased frictional losses when the ambient temperature was lower on the outbound trip. Think tires, hubs, and transmission all contributing their share of drag.

 

But, Friday I drove from Fredericksburg to Clayton, NC. 230 miles each way ambient temp stayed about 12F. All highway cruise control, had to tailgate a truck to get up to 26 MPG. That was with gas from home and gas from NC.

On Wednesday, from Manassas, VA to Fishkill, NY. 390 miles each way ambient temp below 12F Cruise Control most of the way only got 24 MPG. That was on gas from Northern VA and Upstate NY (if Fishkill is technically "upstate",30 miles S of Poughkeepsie). Same both directions, sort of like running the A/C, but not even running defroster.

 

Hmmm....Interesting considering the variations in temperature and fuel sources, we really need an emoticon for a baffled shrug.

 

That's what she said?
That's why I checked. During 70F weather I usually get 30-32 MPG highway, in the 30s only 27ish.

 

I don't know. I have my doubts about climate change causing the low mileage. More than likely Obamacare is to blame.

 

Will somebody translate that for me?

 

It's null and void anyhow. MTBE is mentioned, which supports and older idea/explanation. The Federal Government has banned the use of MTBE for probably about 7-8 years now.....maybe more. Ethanol replaced it.

Actually, it's probably correct. Ethanol, essentially, has the same effect as MTBE.