2012 LT Fuel mileage & fill

[vballt]

I know I saw a few threads when I googled this, but can't find them here, so pardon this newb....

I bought a used (20,000 miles) 2012 LT A/T. I've put 5000 miles on it in the 6 weeks I've owned it, & the best mileage I've gotten so far is 34.1, but I'm averaging 32.9 (DIC says 35.1 avg over last 3000 miles, but that issue isn't as important to me), and I drive 90% hwy, and about 70% of that is @ 60 mph. I realize the winter fuel blend here in OR/SW WA is a lot worse than the advertised 10% ethanol, but that is still a far cry from the 38 advertised.

I also have not been able to put more than 9.9 gallons in the tank (OR they pump for you, but I've tried a few times myself in WA with no better luck), and I believe this is supposed to be a 15.6 gallon tank!

Any advise on improving my mileage or filling my tank to somewhere near capacity? I don't like filling up every 2 1/2 days (as I drive 130 round trip for work every day)!

[epcotbob]

Maybe the fuel gauge is bad? It is a 15.6 gallon tank, so when it's full, you have 15.6 gallons.

I think your mileage is about normal for winter and your mix of driving.....38mpg is best case, 100% flat hwy.

[obermd]

The DIC has a fuel consumed display. Reset it at the next fill up and then compare this display to your gas pump the next time you fill up after you reset it. Post your results. Also, when you fill up, where is the fuel needle pointing?

[vballt]

I don't think I realized the DIC had a fuel consumed display, I'll have to look for that.


The needle is usually between the 15/16 mark & the full mark, never at the full mark. I've run it down to as far as 30 miles past the low fuel light, that's when I filled 9.88 gallons.

[bodeis]

My eco is like that. It will only ever take 10 to 10.5 gallons before it clicks off. I've driven over 100 miles after the light came on and guess how much it took? You got it, 10.5 gallons. Today I sat there for about 10 minutes until i got 12.6 in which is what the eco is supposed to take. Had my fuel level sensor but it didnt do anything. I honestly don't know if there is a fix. Such a silly setup on these cars. Makes me wonder about mileage claims. Filling to the first click, at least in my case, is horribly inaccurate if your trying to figure mpg.

[vballt]

Yes, & I have always done fuel economy every filling of everyone of my cars the last 10 years! I can tell you there is definitely more than 10% ethanol in the fuel, prob closer to 20% from the end of October til April (or water &???? added to pad the sales profit for the oil companies). Frustrating to have to go through all of that to completely fill your tank (which I can't do in OR because I can't pump my own fuel). I would definitely love to have that whole 15.6 gallons though!

Now that I found the fuel used part of DIC I'll have a closer watch. I'm sure it will come down to just having to live with it though.

[Sunline Fan]

When I fill up and pull it out after the first time of it shutting off, there's only 14.xxx gallons in mine. Onstar mobile app says 90% full just after leaving the gas station.

[obermd]

One of the issues that all sedans have is they're vertically short. This translates into fuel coming back up the fill pipe further than it would in a taller vehicle like an SUV or truck. With the fuel coming up the fill pipe faster, any turbulence in the flow going into the tank get turned into "bubbles" of fuel that rise even higher (think soda coming out of a fountain at your local fast food restaurant). To counter this somewhat, always use the slowest (first) hold point on the nozzle handle.

For example, I put 11.6 gallons into my ECO MT yesterday. It had an estimated (based on the DIC's remaining range display) 1.3 gallons in the tank when I started. This gave me 12.9 gallons in a "12.6" gallon tank. The first click off was at 9.8 gallons which means had I stopped at that point I would only have had 11.1 gallons in the tank or 88% full. The car had reported I had used 10.3 gallons since the previous fill up.

[ErikBEggs]

Could be a fleet trim.. wasn't it confirmed they have smaller tanks? Check the VIN to see if it is one.

Also, your fuel economy is a bit low for all highway driving but not too much.. it is winter and cold as ****. How are the temps? By my experience, fuel economy even at full operating temperature starts to tail off rapidly under 40F, with huge penalties as you dip below 20F. Has more to do with the fuel mixtures, cold air, mechanical loss, and denser moist air.

[vballt]

Yes, the weather has been between 25-40 most of the winter, so I know that has alot to do with the mileage. Definitely did notice a decrease at 70 mph on a 28 degree trip last weekend (34.5 on DIC, & that appears to be 2-2.5 higher than actual).

I believe the "E" on my VIN denotes the Fleet trim that you mentioned, so does that mean it actually has a smaller tank? Or the same type of setup I'm hearing about on the Eco with a different neck/sensor to limit the fuel in tank?