DIfferent gas, different MPG

If you would read my original post more carefully you would see that the mileage halfway back to DC from Philly was STILL 21-22 MPG. C’mon… Duh!

I shouldn’t be surprised that the skeptics come out of the woodwork howling as vigorously as if I claimed I was running the car on water. But at least you could comprehend my original post so I don’t have to repeat myself.

I think I’ve wasted enough time on this thread.

“You didn’t really think that “Sonic” gas, or “Astro” gas, or “Sav-on” gas have their own refineries, did you?”

That is not at all what I said. Do people read off the computer screen too fast? Is that why they don’t comprehend?

An independent station might buy gas from one source one week and another source the next week. That brings the possibility of inconsistency. Are you denying that an independent station could be inconsistent when they are buying from different sources each week?

Yes, Avalons can use regular or premium. Yes, it resets on fillup and only then. Your mileage after that fillup sounds much more consistent with what I get on road trips with my Avalon. I did once use an ethanol blend and it was much worse (on a different car). I wonder whether the amount of stops could be different on the two trips? Another thing, I have found on my Avalon that temperature makes a big difference…from freezing to 70 degrees my highway mileage goes up about 4-5 mpg. I have checked my meter against the traditional fill and divide method. One long trip, they agreed well. Another, they didn’t (2 mpg difference). I think on the second trip, the reason was that I filled the tank in the morning and refilled in the afternoon, when it was warm. The gas expanded in the tank; in this case the fill and refill method was apparently LESS accurate. Anyway, I have experienced the “know it all” thread response, my sympathies.

Sounds like something may be screwy with the mileage computer. I’ve had several vehicles with these gizmos, and you have to reset them manually. Unless, of course, you are reading instantaneous fuel economy, rather than average fuel economy. If you are looking at the instantaneous reading, forget it! Having just a slightly lighter foot on the gas would account for the difference you found, in the short run.

Well on a car that recommends high test you can use either, but using regular will reduce the mileage and power. Since octane often differs from one supplier to another (even when they are the same brand on the pump), you might get different results. Once the octane gets up to the recommended level, going higher will make no difference in mileage.

Trust me, my friend, I do not have a problem with reading comprehension. As we apparently both acknowledge, independent gas stations buy whatever gasoline is available, from whatever major brand gas companies are selling excess odd lots of gas stock at any particular time.

However, since nobody (except perhaps a marketing concern hired by a gasoline company) has ever shown a difference in gas mileage from one brand of gas to another, the most obvious conclusion is that your methodology and/or your theory is flawed.

While the source of the gasoline at independent stations is inconsistent, there is no evidence that one brand of gasoline yields better gas mileage than any other brand. Therefore, it does not matter which company supplied gas to Sammy’s Gas and Go on any particular date. As long as the gas was not contaminated with water, the engine will perform the same with the “discount” gas as it would with name brand gas, and as long as the discount gas did not have a high level of ethanol in it, the gas at that independent station is going to produce the same gas mileage as the gas from any name brand pump.

The same vehicle can produce different results in gas mileage, given the vagaries of different drivers, different temperatures, different wind conditions, and different driving conditions, and that is what you undoubtedly have observed.

I googled “Avalon mileage computer” and found a bunch of complaints about how the mileage computer resets every time the vehicle is restarted, so the OP is correct in that respect. The poor design (from what I read, you can’t change the settings to record lifetime or trip mileages) doesn’t inspire a lot of confidence in the accurancy of the calculator.

I’m with the other responses that said your methods were flawed. To have a valid test, you’d need to:
-Drive the exact same course
-Use one driver driving in a consistent manner (with little traffic to cause slow downs/stops)
-Perform the test under the same wind and weather conditions
-Drive until the tank is nearly empty so you don’t mix brands of gasoline
-Calculate the gas mileage by dividing the miles driven by the gallons you refill the tank with

If you didn’t do all that, you can’t say that the only possible factor in the different gas mileage was the gas itself.

Hi circuitsmith. Your asertion is a valid one for a couple reasons. 1. Company stations sell what is known as Tier 2 gasoline - better grade gasoline than independents who sell Tier 1 gasoline, which is a noticeably (for your car) lesser grade, therefore your vehicle responds accordingly. 2. This is personal experience. My wife, who used to buy independent gas switched to Shell because Shell just put in a station across from her office and it was convenient for her. She drives the identical route - 40 miles one way - 5 days per week. She told me of an increase in mpg of 4 - 5 mpg according to her record-keeping. I would not accept that at first - assumed it was due to some error in calc, however, once I found out about Tier 1 and Tier 2 gasolines, I had to concede my wife’s calculations could be right. We then kept records for the next 7 months and sure enough, her mpg had increased just over 4 mpg. I think 7 months of record keeping for those miles travelled is pretty significant. I have since switched to a company gas station, except mine is Mobil.

One thing I haven’t seen mentioned is that indies can sometimes shop around for the best deal on wholesale gas. This may mean getting a tanker full of winter blend (high volatility) that the big names were trying to get rid of as weather warmed up, or vice-versa (summer blend in cold weather). And of course, ethanol levels vary. Just another bit to confound results.

Who knew that this was the controversial issue of the decade!? Why all the emotions, guys? circuitsmith is simply reporting his experience on a matter of general interest, not claiming to have disproved entropy in the second law of thermodynamics. Cut the guy some slack.

On the other hand, the whole point of posting to these discussion groups is to elicit broader responses that may not always agree with your premise or conclusions, circuitsmith. Stop pouting, it’s just a discussion!

Isn’t it funny how those who have nothing to say accuse those who do have points of being emotional? Some folks need to get away from the 70’s tactics of stifling discussion.

I got a similar situation. From Jersey City to Burke VA and back. I dont have those hi-tech gas gauges but its pretty obvious that the gas I got in VA was supperior. Jersey city to Bruke - horrible 22 MPG on the way back 33+ MPG. The gas came from the same company - Shell. Im currently trying out differenct gas stations around my neighborhood. I did find an gas additive for injection cleaning that gives me outstanding MPGs but its expensive. around $6 for every fill-up. Defeats the purpose of improving the MPG of your car. If gas prices get back to around $4+ then its worth it.