I bought a new 2006 Prius last year and have pretty much exclusively used Phillips 66 87 octane gasoline for over 19,000 miles. My average was from 40- 43 mpg. Got into a pretty big tiff with Toyota about the misrepresentation of their car and was about ready to have it declared a lemon.

Last week I filled my empty tank with Shell 87 octane and drove a few hundred miles. I saw an increase of 3 mpg. Filled again, another increase. Drove 360 miles to Kansas City and returned using Shell gas. My t-t mileage is about 49 mpg now.

I realize four tanks doesn't prove anything but the trend is very good.
I checked with a friend who manages a number of Phillips stations and he said it is the additives.

If you're getting lower than average gas mileage then go to other brands with an empty tank and try a few tanks for trending. Always 87 octane.
Let us know how it works for you.

More likely your driving style changed. Or your car is just now getting broke in.

You wrote: "More likely your driving style changed. Or your car is just now getting broke in."

My driving conditions remained the same. The change in mpg was immediate from the first tank. On the way back from Kansas City I was driving into a constant 25 mph wind at 70 mph on cruise control for 270 miles or so and got 49 mpg t-t.

I will log a few thousand miles with Shell and record the mpg then switch back to Phillips - one tank should tell.

I spoke with a friend with Reasearch and Development at Conoco-Phillips and was told it is probably the additives. This person was interested in knowing if I get the same mileage at stations away from the region I live in. I mentioned that I had filled at Kansas City and the trend is continuing. I plan on filling my other cars at Shell to see if there's a difference in them too.

It's a fun experiment that could wind up saving me 20 cents a gallon or more!

The EPA reports considerable difference in the energy content of brands of gasoline too. I'd known Sunoco was pretty good but hadn't tried Shell. It is worth a tank or two just to know.

This is one of those cases where I wished I had a 'portable' calorimeter.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
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Are you factoring in weather? The fuel you buy during the winter month is different than the fuel you buy the rest of the year. Could that be it?

Warmer weather in itself will give you a nice boost in fuel economy.

Harry

President Bush on Global Warming:

http://www.glumbert.com:80/media/globalwarming

Considering they all get the fuel from only a few sources, the gas is the same except for the additives each company adds, this kind of makes sense. But if you get better mileage I have to think maybe it is not the best fuel for the long haul. Chevron uses Techron in their fuel and this keeps the engines cleaner, it is hard to believe their fuel gives less mileage than Shell.

It's an interesting theory, and I'm sure that experiments have been done. Anyone have a place to look for data on this? I always assumed that a given level of octane was pretty much the same at any gas station and I hardly ever buy gas at the same place twice in a row, because prices change so much from station to station around here and you never know which one the cheapest will be until you check them all.

The variation is incredible, and a lot of it has to be competition, so you'd think that their additives would have to be pretty similar if they want to stay so competitive and flexible to meet the prices other places offer. Unless the additives are cheaper than the gas- anyone know if that's the case?

livvie wrote: Are you factoring in weather? The fuel you buy during the winter month is different than the fuel you buy the rest of the year. Could that be it?




I purchased my Prius in March 2006. Initially mpg was 37 and I took it back the next day. It increased to 40- 43 mpg over the next few thousand miles. Sometimes it gets better, sometimes worse but it has averaged in this range.


I noticed a decrease in mpg when temperatures got over 105 F as I drove through Texas last summer. Mpg increased a little as I drove into higher and cooler altitudes of NM.


My Prius mpg has been fairly consistent through the seasons for the year I’ve owned it.


About the fuel: according to my ‘in’ at ConocoPhillips, all of the refineries manufacture their fuel to specific standards and dump it into one common pipeline (kind of like electrical power companies produce electricity and push it on the grid). This is true for gasoline and diesel. Essentially all of the gasoline (and diesel) loaded into tankers is the same – only the additives are different and they are added either at the loading terminal or at a different location.


I do not know if the additives have been changed through the years. If they have not, then they were developed for automobiles of another generation. The additives won’t change unless the big companies notice a decrease in pump sales.


Non-name brand gasoline is not consistent. Some of that gas is bad and should be avoided because a few pennies saved in the short haul will and could easily produce big problems in the long run. Stay with name brand gas as their additives are fairly consistent.


As I’ve already stated, four tanks of Shell 87 octane isn’t anything absolute but I like the upward trend. I just filled the tank again. My wife is driving the Prius into Oklahoma and will have to refill before she comes home. Hopefully she’ll find a Shell station but she’s going to keep the receipt for filling with the car mileage. (Just talked with her – she’s not using cruise control, is running 75- 80 mph and is driving through heavy traffic. The car is indicating 47.5 mpg – better mpg it got a few weeks ago!)


I don’t know how long it takes these car computers to stabilize out. It seems like mine took about three tanks.


I am interested in learning what fuels other hybrid drivers are using consistently and what their average mpgs are. If you are getting below what you expect then switch to a different name brand gas and run several tanks of the same brand through. See what happens - all you can save is money. You have to know your current mpg to reference a change. For this experiment all you need to do is reference your onboard computer mpg because you're looking for a trend. T-T will work too but it's best to average mpg over many tanks because you don't know that you fill the tank to the exact same level each time. Either test will work as long as it’s consistent. And always use 87 octane.


Ray

Up until today I had been using Shell very consistently but with widely varying tank averages even by the MFD. The two main driving factors seem to have been weather (below freezing bad, above freezing good) and driving cycle (hilly highways bad, open back roads good). Looks like my displayed averages hit a low of 46.1mpg over ~250mi that I attribute primarily to a snow storm and a high (today) of 56.2mpg over ~280mi that I attribute primarily to the arrival of spring-like weather. Filled at the same Shell station for both of those tanks and drove roughly the same way. So there's a pretty wide variation, and the trend is consistently upward at this time of year. (Just don't pay attention to the hand calculated values in my gaslog because fill inconsistency puts them all over the place...look at the MFD readings in the notes.)

I could see how high-quality detergents would play a role over the long-haul. But we're talking about a 10-20% difference over the course of a few tanks. That tells me either that other factors changed, or that the original fuel was contaminated or otherwise defective.