17/19mpg avg to 25/28mpg?!

[Namuna]

So this past weekend was the first time I've filled my tank since buying my Stinger GT (it came with a full tank from the dealer). I drove it all the way till the meter was on 'E', then filled it with 93octane from Sunoco.

Before the refill I had been a bit frustrated that I wasn't getting anything near the rated MPG range (even easy driving on 'Econ' mode). The average mileage indicator was typically in the 17mpg range regular driving and up to 19mpg on the highway.

But after filling up with 93, I was on the highway to go visit family and all of a sudden the average mileage indicator was showing me 28mpg!!! When I got off the highway and was on regular streets I was down to between 23-25mpg!!

Now I don't know what the hell. Should I believe those numbers? Maybe the system is a bit out of whack having jumped from whatever concoction of low-grade gas and horse piss they initially put in the tank and jumping to high-grade? I had a bit of shell-shock seeing that it cost me $45(USD) to fill my tank with the 93octane, but if it's going to up my mpg by that much then it lessens the pain!

 

[BlaydeX15]

It's hard to tell. If the stinger was test driven, it's likely that the average is trashed. As you add more miles to it, it will start to average closer to the mileage you're getting. I would never trust the reading in the cluster though, they're consistently 10% high. Do the math when you fill it, and that will be much closer.

My average tank is 25.6 MPG though, so the car is plenty capable of 'good' mileage.

 

[Kamauxx]

Only 19mpg hwy sounds like the dealership may have filled it up with e85. Call and ask them what fuel they use.

 

[PHL Mike]

I messed up two weeks ago and filled my GT2 with regular gas and my MPG went way down. These cars are engineered to run more efficiently with high octane.

 

[StingerNYC]

I put 1600 miles on the round trip to chicago last week and on the way there I used 93 octane and averaged around 26mpg. This is nearly entirely on I80 using eco mode at 82mph. On the return trip I decided to try 87 octane and my mileage actually went up 1mpg. This is all from the gauge cluster though. In December I will be going on a 3000 mile trip and for that I will track with an app to see what the real mileage is.

 

[Audible Silence]

Pen and paper doesn't lik. I've read the digital indicator can be off 1 or 2mpg

 

[Jwolf]

The dealer probably put in 87, but better fuel, up to what it is tuned to be able to handle stock, will give you better efficiency most of the time. Also, as it breaks in your mileage will go up a little bit.

And shoot consider yourself lucky. It costs me around $60 to fill up with 91 octane in California.

 

[Namuna]

Thanks for the reply folks, looks like I'll have to go OG and manually track the mileage to get the truth.

 

[Doel]

Pen and paper doesn't lik. I've read the digital indicator can be off 1 or 2mpg

the problem with this type of calculation is that different fuel pumps, and even the same one, won't fill up to the same volume each time, temperature will also change fuel density.

And shoot consider yourself lucky. It costs me around $60 to fill up with 91 octane in California.

Can't say I'm a fan of the politics here but filling up with 93 octane for $38 isn't too shabby #thankscostco

 

[rocket23]

One tank +4 more....for a general all around ''feel'' for your mpg's,driving habits and terrain.....no one will have the same reading. ,jmho.


ps. and use the same fuel

 

[Never thought]

Using top tier fuel may increase mpg as well.

 

[Paul32]

Using top tier fuel may increase mpg as well.

The biggest factor is lighter shoes.

 

[rocket23]

tighter shoes.....

 

[Mike_TX]

It seems to be SOP to denounce a car's fuel mileage calculator as always being optimistic, but given that it measures actual fuel flow and the resulting mileage based on actual miles driven, it's kind of hard to question it.

It's more accurate than using the readout on the pump, since gas pumps aren't all that accurate themselves, and then you have to account for "air bubbles" in the tank, slight differences in the angle of the car in the station's driveway which can affect the tripping of the nozzle cut-off, the density of the fuel based on its temperature, etc., etc. IOW, you're never going to fill the tank exactly the same, and the inaccuracies in the pump readout and in your odometer have to be considered, so the whole process of manually calculating mileage is flawed from the start.

I've run tests on cars before, and found the averaged difference over several tanks to be very small. The only way you could really accurately compare mileage is on a test stand in a lab with very precise measurements and in a carefully controlled environment to eliminate all variables, and the car's calculator is probably as close as you're likely to get. You're free to disagree, of course, but I just rely on the car's readout.

 

[BlaydeX15]

It seems to be SOP to denounce a car's fuel mileage calculator as always being optimistic, but given that it measures actual fuel flow and the resulting mileage based on actual miles driven, it's kind of hard to question it.

It's more accurate than using the readout on the pump, since gas pumps aren't all that accurate themselves, and then you have to account for "air bubbles" in the tank, slight differences in the angle of the car in the station's driveway which can affect the tripping of the nozzle cut-off, the density of the fuel based on its temperature, etc., etc. IOW, you're never going to fill the tank exactly the same, and the inaccuracies in the pump readout and in your odometer have to be considered, so the whole process of manually calculating mileage is flawed from the start.

I've run tests on cars before, and found the averaged difference over several tanks to be very small. The only way you could really accurately compare mileage is on a test stand in a lab with very precise measurements and in a carefully controlled environment to eliminate all variables, and the car's calculator is probably as close as you're likely to get. You're free to disagree, of course, but I just rely on the car's readout.

I use the same pump at the same station every time, because it's 30c cheaper. Lol. That's about as close as you can get to replicating fueling.

Nothing is really 'perfect', but my trip computer tells me that I always get between 30-31 MPG on my commute home, which is basically impossible. I don't trust the trip computer to be more accurate than the manual math method. Plus, manual math calculates the mileage that you're actually paying for, so it has at least some kind of basis in reality.

Edit: Some car sites have tested it too, and find the car's readings to be 5-7% high on average.
Why Your Trip Computer Isn’t Giving Accurate MPG Readings (And How to Fix It) – Feature – Car and Driver
Your Fuel Economy Gauge Is Fibbing | Edmunds
Should You Trust Your Car’s MPG Display?

 

[Never thought]

The biggest factor is lighter shoes.

I disagree. I put on rotary forged wheels that saved 10lbs on each wheel. I saw no real mpg improvement.

 

[Kamauxx]

I disagree. I put on rotary forged wheels that saved 10lbs on each wheel. I saw no real mpg improvement.

I think he means being light on the pedal.

 

[Never thought]

I think he means being light on the pedal.

Oh... haha!

 

[Paul32]

It seems to be SOP to denounce a car's fuel mileage calculator as always being optimistic, but given that it measures actual fuel flow and the resulting mileage based on actual miles driven, it's kind of hard to question it.

It's more accurate than using the readout on the pump, since gas pumps aren't all that accurate themselves, and then you have to account for "air bubbles" in the tank, slight differences in the angle of the car in the station's driveway which can affect the tripping of the nozzle cut-off, the density of the fuel based on its temperature, etc., etc. IOW, you're never going to fill the tank exactly the same, and the inaccuracies in the pump readout and in your odometer have to be considered, so the whole process of manually calculating mileage is flawed from the start.

I've run tests on cars before, and found the averaged difference over several tanks to be very small. The only way you could really accurately compare mileage is on a test stand in a lab with very precise measurements and in a carefully controlled environment to eliminate all variables, and the car's calculator is probably as close as you're likely to get. You're free to disagree, of course, but I just rely on the car's readout.

I have compared more than 50 fill up's and all were optimistic based on the car's computers. If there were variables in the pump fill ups, one would think they would be plus and minus. I'll rely on my calculation like I have been doing for the past 60 plus years. Every car I have ever owned with a computer was optimistic.

 

[Never thought]

I have compared more than 50 fill up's and all were optimistic based on the car's computers. If there were variables in the pump fill ups, one would think they would be plus and minus. I'll rely on my calculation like I have been doing for the past 60 plus years. Every car I have ever owned with a computer was optimistic.

Agreed. But the cpu isn’t far off. I’ve calculated it a few times and it is always within 1-1.2 mpg. My Optima was off by 3 mpg.