New tank, better MPGs?

[merigayle]

Hi All. I rarely get gas, about once a month-6weeks. My last tank SUCKED. I got 44.1mpg for the tank. Previously, I was getting 50-52mpg on average. Well, I filled up at a different gast station yeterday morning and my mpgs for yesterday were 50.4. So, back to where they were! I know we had some hot weather last month, but i rarely ran the AC and when I did it was in Econ mode. Could it really be the additives in the gas or some other variation in the brand?

(it was really sad to be getting such low mpg's for 6 weeks!)

[b1shmu63]

Are you determining your fuel economy by using the trip MPG guage, or are you calculating it bydividing the mileage by the amount of fuel filled at the station?

[merigayle]

Hmm. The trip guage said 44.1

I went about 450 miles and got 10.2 gals of gas.

Is the trip meter not accurate?

[Resist]

Originally Posted by merigayle

Could it really be the additives in the gas or some other variation in the brand?

You didn't say what grade or brand of gas you used. Or what the outside temps were. Or what your tire pressures are.

[merigayle]

I do not know the tire pressure. The last tank was either Wawa brand or Hess, i forget. 87 octane. This time, 87 octane Exxon.

I told my husband to check the tire pressures. (he's a mechanic, gotta put him to use )

It was hot over the past month- sometimes into the 100's. Would the heat, even without the AC on cause that huge of a difference?

The mpg's were actually around 41-42 until the past week when i got them up to 44.1
My lifetime went down too.

[Resist]

Originally Posted by merigayle

Would the heat, even without the AC on cause that huge of a difference?

Outside air temps make a huge difference in fuel mileage. Warmer temps will give you better mpg than cooler temps. But if your tire air pressure suddenly dropped, that could also lower your mpg.

[merigayle]

I will have him check the tires when the rain stops eventually and report back!!

But, if it were the tires, then i would not get better mileage on this tank, no? Maybe it was a whole combination of factors last month.

[b1shmu63]

Sometimes measuring the mileage by amount filled is inacurate. In this case it seems to agree with what the resetable trip fuel efficiency gauge is saying, so this likely is your true mileage. All other factors being equal, warmer weather should increase your mileage. Since this didn't happen you should keep an eye on the mileage for a while to see if there is a pattern developing.

[originalbadbob]

I have gotten some less than ideal gas on occasion. One tank would be normal, and the next would be at least 10 mpg less for the same commute/driving etc. Then the next tank would be back to normal. Temps were about the same, tire pressures ok...etc.
It was a brand name station that I used to do business with almost all the time. I switched stations and I am able to count on my mileage within a couple mpg.
robert

[dice]

my right foot is the biggest determining factor for gas mileage.