I've had a 2005 for 18 months, put on all 12400 miles and NEVER GOTTEN MORE THAN 200 MILES ON A TANK (ie. 14 MPG in 14 GALLONS). I know the tank is 15.9, but every time my empty light comes on and I re-fill, it refills to 13.8-14.2 and I've done about 195-200 miles.
So a guy I work with has an automatic (dont ask) 2004 and stalled due to using CITGO gas (according to the Mazda tech). After hearing this, I read some threads and decided to do 100% SHELL 93 ALL THE TIME.


FIRST TANK: 245 MILES (17mpg), SAME DRIVING STYLE...IN FACT I'M IN FLORIDA SO MY A/C IS CRANKED NOW.

So am I smoking something or is Shell a 3mpg boost for us?

 

different gas = different results

one time i've gotten 75 miles from Shell 87 octane in the first quarter of the tank. Don't ask me how. IT NEVER HAPPEND AGAIN.

anyhoo, I've had my mpg's decrease from using 87 consistently (3+ tanks) AND then going back up after going back to 93.

Different companies use different blends and it even seems to me that different stations of the same brand have different blends (based upon the performance of the car). I'm still looking for that station with the magic mixture.

 

Where you get your gas MAKES a difference...Shell is up there! Avoid those cheap no-name brand!!!! Check:

http://www.toptiergas.com/

I use 87 and get 18-19mpg on a pretty regular basis when doing mostly city driving...

 

My service guy was like "Use Exxon because they put stuff in it to keep the throttle body clean." So i do. And I get a constant 17-19 from it. Not bad. I dont drive with a heavy foot...that often. A redline or two a day. Becuase it's a blast.

 

Note:
Top Tier is a marketing campaign that the companies involved pay to be included. There are other companies that sell the same quality gas (e.g. BP) that you won't find on that list.

 

I wont use arco gas because of past experience. I wondering if Costco/fred meyer/Safeway gas is the same quality as shell, BP, chervon.

 

the only gas i can get around my area is sunoco and mobil. I wish i can try shell out.

 

True..but, BP isn't considered a cheap no-name brand..it is well known..so chances are, they are refining it and adding their extra additives to help our 8 get better miles. I stopped by one of those no-name brand (Space Age) and drove no more than 10 miles and it sucked a 1/4 tank!!! So..yeah..one will have to try various brands until you find the one that works for your car. Just a good starting point..even if it is a marketing gimmick..

 

ahh...... That was E85 you were using.

 

i also live in florida & use citgo regularly b/c it's some of the cheapest. i constantly hit 200 miles per fillup just like u bro.
i dropped off my car this morning at potamkin mazda for my 15k mile service & was told by the tech to use chevron for better gas mileage. i'll give it a try & post my results...

 

Yeah, Chevron is good too..however, I'm leaning towards Shell because I have this lovely visa card from Shell that gives me back 5% on all gas purchases made at Shell station Stations that I recommend that I got decent miles are:

Shell
Chevron
76/Conoco

 

Not sure if this is urban myth or not, but, what time of day do you fill your car? Early in the AM, when the gas in the underground tanks is cooler, it is denser, so, when the gas pump says 10 gallons it is giving you more gas than the same 10 gallon reading at 5:00 PM. Suppose it is possible, I don't know how the pump measures...volume or flow...? Every article on improving fuel economy always says to fill in the early AM.

 

I read that same thing somewhere too. I think they said that it was measuring the volume of the gas you were getting so say at 5:00 A.M. the gas is colder the the volume is more condensed so you get more gas for the same price. At 5:00 P.M. the gas has expanded more due to rise in temperature and you get less gas for the same price, that is, because the pump reads it as volume... I think, well, that makes more sense to me at least. Too bad I just filled up my tank at 5:00 P.M. with Shell and got 18.5 mpg.

 

I can't see it making an appreciable difference. What if the gas station is across from your work, and you get a fillup early morning as you arrive? For the "denser gas" theory to have any appreciable effect on mileage, the density change with temperature would have to be large enough so that by the time you walked out to your car in the afternoon you would have leaked a bunch of gas from overflow as it expanded. This doesn't happen.

Also, the storage tanks are buried deep enough, and the amount of fuel stored is a large thermal mass. I doubt if there is much temperature variation in the storage tank over the course of a day.

 

5/1/06 - Revi + Ram Air - 24,000 miles + installed new spark plugs with the Revi. – OEM tires, exhaust, 91 octane.

Mileage – 1st tank city, 21mpg + 1 over standard 18-20 – 2nd tank freeway cruise 23mpg + 2 over standard 20-22 - 3rd tank rush hour freeway and city, 21mpg. Overall, 1-2mpg better.

 

Funny but I switched to shell gas,,, V-Power 91 octane.
And I noticed the same thing ,,increase in fuel economy.
I drove across town to the kids house (70 miles)and barely used an 1/8th of a tank.
I thought the gauge was stuck or something like that.
And I drive 80mph plus. I am useing Shell all the time now.
I seem to be getting around it seems if I stay on the freeway only, I will get 250+ miles per tank full.

 

Normally, for me...on the highway w/ 93 octane from fill-up to the low light I'm getting 290 miles. Sometimes I can push 315.

 

First, I did state my disclaimer that I didn't know if this was a myth or not. I don't think that anyone thinks that you are getting any additional fuel...the tank is full when the tank is full. You are taking advantage of an inadequacy of the measurement capability of the gas pump. If it reads fewer gallons you are getting charged less and your mpg calculation will come out better.

As far as the volume in the tanks. It does change. Way back I was a gas jockey and we used to stick the tanks to check inventory. Late in the day the level would rise in a tank that was not being used.

 

This is the way it is or was. A gasoline truck driver starts out the day with 10,000 gallon in his truck. He delivers that 10,000 gallons. During the day the gasoline expanded and he still has 1,000 gallons to sell using simplified acounting and no paper work. Mickey sells air in his milkshakes too. What happens to that gasoline when it cools down? I am guessing the low price offsets any shrinkage.

 

Hmm I constantly maintain well into the 300's using 93 octane from shell. Usually can get about 320-350 out of a tank ...can bet that I would get 360-380 if I ran it dry

 

if im on the freeway i get over 300 per tank but in town i only get in 250(if that)

 

im partial to 76 gas because of the business gas card but 76 and shell are both excellent shell is just a bit cheaper

 

I don't doubt that there was a measurable change, but whether it was a large enough change to make any meaningful mpg difference. Do you have any recollection as to what *percentage* change there was? To make 1mpg difference in an rx8, it would have to be something like 7 percent. And I get back to thinking that if there was that much expansion potential we would have cars leaking lots of gasoline as full tanks of cold fuel expanded. There's room in the plumbing for some expansion, but not a gallon.

 

i get 15mpg no matter what
i only use 91
and i drive like a jerk everywhere

 

Recollection of percentage... uhhh I don't remember what I had for breakfast.

I doubt that anyone would be suitably motivated to figure this out. I do remember that the tanks were in the 10k gallon range and the the sticks were at least 10 feet long and the differences could be about 2 - 3 inches. Of course this is highly non-scientific considering that the bottom of the tank was curved and no self-respecting 15 year old was going to get the stick exactly centered every time.