Gas prices have dropped -- so has my milage

I'm not a fanatic about checking mileage at every fill-up. But my car has a readout on the dash that gives average mpg and I check it ocassionaly. Once a week or so. My car is a '09 Corolla and I was getting, on average, 33.2 miles per gallon according to the dash meter. That was when gasoline was around $3.50 per gallon.

I noticed something over the past few months. Since the price of gasoline has gone down, my mileage started dropping. A few months ago, the price dropped to around $3.25 per gallon. Shortly after, my mileage started dropping and settled at 32.8 mpg. Recently, gas prices have dropped again to $3.09. Sure enough, my mileage started dropping again and has settled at 32.2 mpg. My driving habits haven't changed and I do regular maintenance.

This a graphic showing the calculations I did to determine the cost per mile in relation to miles per gallon.



The cost per mile has dropped slightly. However, with the mileage reduction, my savings are nowhere near what they should have been. My car has a 13 gallon tank. According to the price difference, I should be seeing a saving of $5.33 per tankful (WOOHOO! - beer money ). However, with the reduced mileage, my actual saving is 13 cents per tank. Not even enough for a pack of ramen.

I wondered if anyone else has noticed this. I also wonder if it's possible the oil companies are tweaking the mix to keep their profits up. Granted, I've been using ethanol blended gas. Maybe I should try the regular gas to see if it makes a difference.

So, what do you think, folks? Am I just imagining things?

no, its winter, most companies oxygenate their gas in the winter from what I told, its cheaper gas, but burns faster

I want to say I have to agree. I do keep an eye on it and it seems as if I am going to refill about a day or two earlier than what I normally had. I have never actually started doing the math and see for sure but something does seem to be off. I have never said anything because I was not sure if it was me or not but it has been a few months when I first started noticing it. I think I will start doing the math and see.

reply to post by HomerinNC


That did cross my mind. I wondered if weather and temperatures could have affected it. But the first mileage drop I noticed came during the summer.

In Australia I've seen the same thing, I put it down to companies using ethanol blends in there fuel.
This makes it cheaper and the pump but as a result less mileage per tank.

It might be worth trying out a few different stores or even try a tank of premium to rule out fuel quality.

Been watching the prices as well. Statistically it is a seasonal thing.

Prices change seasonally. Usually prices are highest in the summer and lowest in the winter. Blends change to. EPA regulations say that summber blends must have a specific range of Reid Vapor Pressure (RVP). This is to eliminate fumes escaping during the fueling of an automobile at a gas station. Therefore the RVP is higher in the winter and lower in the summer.

Specifically, butane is added to winter blends. Most refiners would love to add as much butane as they could, it is cheap and has good energy density.

I disagree with the ethanol theory. Ethanol is added to oxygenate the fuel. This was once done by using methyl tert butyl ether (MTBE) but is no longer practiced. In the 1990's some refiners used ethanol blends, this lead to a common vapor lock problem in automobiles. One of the refiners not using ethanol was Shell and their gasoline became very recognizable because of their ethanol-free gasoline. Though nowadays the ethanol problem has been solved by better blending techniques.

reply to post by N3k9Ni


Where are you? Here in SE wisconsin we are FORCED to buy gasoline with 10 percent ethanol in it, which reduces mileage....oh and subsidized by tax payer dollars.

Taxpayers just can't get a break on either end...

reply to post by N3k9Ni


I paid $1.40AU a Ltr today for ULP and for Vortex I pay on average $1.60AU a Ltr.

ouch

I hope the price goes down. It is outrageous!

Use the regular gas, the other isn't worthy of any documentation......unlesssssss, you have been using it all along. In order to have a constant, you need to have a constant. Would like to see your figures. I give you S&F for your effort. Hope you respond with some numbers.