Differnet gas nets 10mpg gain

This reply is only addressing your text that I quoted.

Agreed! The point that some people may miss is that it is extremely dependent on other factors that also affect mileage, such as whether your engine can take advantage of it and your driving conditions. I mentioned this in a prevous post. While regular is O.K. for our 2000 Avalon XLS, premium is recommended. We see little difference, if any, in mileage for my wife's commuting back and forth to work. Lots of stop and go, creeping along to the next stop sign or traffic light kind of traffic, which can only take minimal advantage of the additional power. We do see an improvement in our weekend drivng where speed limits are above the 25-40 my wife encounters on the way to and from work, and the engine can take advantage of the additional power. I have my SGII currently on the Avalon also, and, while I have not keep a log of HPR, I have noticed smoother running and a quicker response to the throttle, quicker increase in HPR. Remember this is metro Atlanta and extremely hilly terrain. I believe, not sure, but it could be more torque. I'll have to chart RPM vs HPR. It really is quicker and smoother with the premium. As a result I can go easier on the throttle and have seen an improvement in MPG. I realize this is anecdotal, and only one persons observatons, take it or leave it. The only skin I have in the game is my wallet.

 

I don't really care to get in the middle of the discussion here. but I must say that phrase made me chuckle.

 

Michael, you don't share with us where you are.

I'm interested in an English manor, maybe like this one:

 

Just for fun I filled up with super. So far, my MPG is up from 52 to 56+. I have almost 300 miles on this tank. At one time, without using the freeway, I was at 59 MPG. with mixed driving my MPG is still about 3 to 4 MPG better than I normally get.

 

spellers and non-spellers are easily recognized and its hard to imagine anyone getting on someone for an occasional mistake. but anyway, not the point...

i have watched this thread for a while now and
i recommend a more rigorous testing before spending the extra money on premium gas.

premium does not benefit you (it will hurt you over time in any normal car) unless you have a high compression engine. the higher the compression, the more power and less fuel you use to get somewhere....the Octane is added to MAKE FUEL BURN MORE POORLY by raising its flash point. the more you compress preheated air, the hotter the air gets. lower Octane gas has a tendency to spontaneously ignite too early if compressed too much causing ping, loss of power, etc

this requires a much hotter spark in lower compression cars to ignite properly. without that hotter spark, the higher compression, you will lose some of the energy that the gas has....and Premium actually has slightly less energy than regular

 

This is not to nit pick. I want to make sure I am understanding you correctly.

...you will lose some of the energy that the gas has....

or

...Premium actually has slightly less energy...

It was my understanding that the energy is the same in both regular and premium. The difference is that the car will be more efficient, be better able to use the available energy, using the grade of fuel that the engine was designed to take advantage of.

???

P.S. After thought. Unless you mean less energy due to the displacement caused by whatever is added to raise the octane. But this would be true of any additive such as detergent additives, etc.

 

OK, I need to jump in here. I am a chemist, ran a lab at a hazardous waste treatment and storage facility. We processed all kind of waste fuels. We used to run BTU values in a bomb calorimeter that burns the material in 30 atmospheres of pure oxygen. We decided to test what the BTU values are for different brands of gasoline. We tested 120 octane Avgas all the way to various brands of 87 octane auto fuel. The results? For auto fuel, the only real difference between BTU ratings was summer versus winter fuel. Otherwise, all the BTU values fell within a very narrow band on a per pound basis. Avgas always seemed to be the same BTU as summer auto fuel.

As has been mentioned, Octane simply is a measure of flash point. Higher octane lower flashpoint, allowing higher compression ratios. BTU values are within a statistically insignificant range.

My 2 cents.

Note; there ARE differences when ethanol is involved. Seems the QC on how much is added varies. As such from lot to lot we saw variations from the same gas pump in BTU value and tested and found ethanol %'s were different. So the original question, which stations don't use ethanol in their gas is still valid.

 

ok...no need to respond since gungadin did a good job...

i simply need to emphasize "slightly less" ...or maybe i should have said "very slightly less"... to be honest with ya, the volume of Octane is pretty minuscule. either way, i am greatly surprised at the restraint this forum has displayed on this topic which is the only real reason i had been following this.

its fairly normal to be swayed by monikers like "premium", "new and improved", etc... to put it simply, we tend to believe what we want to believe, so i was hesitant to provide any comments at all especially since its already been well established that premium does not give you better gas mileage under any circumstances.

we all know that there are a million variable when tracking gas mileage... i can say without hesitation that the gas you use should NEVER BE CONSIDERED AS PART OF THE FORMULA UNLESS IT HAS BEEN VERIFIED THAT THE GAS WAS OUT OF SPEC OR TAINTED.

99% of ALL GAS is fungible...period. so say what you want, i will not stop you. i only suggest that you gather more data if you feel that the type or brand of gas does make a difference

 

gungadin:

Great post. Thanks. I've also tried to point out the ethanol content can be different from tank to tank at the same pump depending on the last delivery. It is my understanding that Ethanol is added at the last posibble/practicle moment to avoid water absorbtion and can vary significantly, ergo the "May contain up to 10% Ethanol" labels. Emphasis on "May" and "up to". This is why I believe that is extremely difficult to micro manage or track MPG to analize the affects of different habits or brands or stations or tire, etc., since the "margin of error" due to the fluctuations in the ethanol content can skew any observations of the other variables that you may be trying to analize. I believe differences are only meaningful if they can be tracked, over a period of time, say 10 tank refills. Then you can feel fairly comfortable that the specific was what affected the MPG.

P.S. I definitely will keep a log as we have on our Avalon since new. However, since the "May contain up to 10% ethanol" labels started showing up on the pumps here in Ga, I was thinking of purchasing one of the "ethanol testers", so that I could determine what if any fluctuations there may be in the ethanol content between tank refills. Has anyone used one and if so I would appreciate your comments or opinions.

P.P.S. It just dawned on me why I didn't purchase one back when I ordered my SGII. I felt the margin of error for the gauge as significant enough to allow any measurments of 10% or less
to be skewed enough to be meaningless. It would probably be O.K. to determine none, 10% range or 85% range, but would be like trying to read a 6" slide rule to 4 decimal places, if using it to adjust for tank to tank MPG calculations.

Thanks again!
Dave