gas discovery

[Nova2009Mazda5]

For the first three tanks of gas in my new 5, I went to the station closest to my house, an Exxon. And the engine seemed to get rougher and rougher with each tankfull, particularly at idle. Well, today I tanked up at a Chevron about a mile away. Noticed a big difference shortly thereafter .... the car is back to purring the way it did the day I bought it.

Not to say that Exxon gas sux or that Chevron is automatically superior (although maybe Chevron's gas additive is helpful), but that as quality can vary from station to station, particularly if a station's underground tanks are old. I'd always heard that, but seeing (driving) is believing.

Anyhow, I guess I'll be buying gas from the Chevron from now on ...

Question: how much gas does everyone's 5 take when filling up? I've been tanking up within a few miles of when the gas light comes on ... on average seems to take about 12.5 gallons. I read that the 5 holds 15.9 gallons. If that is true, then the light is coming on when there is still more than 3 gallons left in the tank, which seems like a lot.

 

[mazdaspeedster3]

I get about the same on fill ups. I will let it run about 20-30 miles past the gas light coming on and fill about 12.5-13 gallons. That is good though so you are not getting to the sludge or junk on the bottom of your tank. I have often thought, I should run this till we run out to see how far it will go but that isnt good for the car.

 

[TheMAN]

rumor has it, exxon gas contains a lot more ethanol than other brands such as shell and chevron... that's why it's so cheap!

yes, ethanol does cause the car (not designed for it) to idle bad and have bad gas mileage

 

[rweatherford]

I can say that the 5 will run on E-85 with little problem. Seems it will set off the check engine light and it runs a little funny.

My wife filled up at the wrong pump. I'm finding that my lawn mower runs decent on the stuff. I've got quite a bit of it in cans since I had to pump the 5's tank out. Smells similar to methanol when it's burned in an engine.


I would not try this at home......

 

[mazdadude]

I ran mine very low once, and put in ~14.5 gallons when filling up. At this point, the gas gauge needle was past the line, past the "E", and was pointing at the triangular arrow that tells you what side of the car your gas cap is on.(eek2)

I don't think you are ever going to get to use that last 1.5 gallons without jeopardizing your fuel pump. Now when I am driving and the low fuel light goes on, I know I have ~50 safe miles before I must fill up. I would love to rent a Mazda5, fill it up, and drive it till it stalls, and then find out how many gallons were left when it eventually stalled.

I drive the wife crazy doing this, as when she is driving, she will refuel before the low fuel light even gets a chance to come on.(blah)

I also have noticed a difference using ethanol mixed fuels in the 5, and stay away from them when at all possible.

 

[coolmazda5]

on average seems to take about 12.5 gallons. I read that the 5 holds 15.9 gallons. If that is true, then the light is coming on when there is still more than 3 gallons left in the tank, which seems like a lot.

Yeah, same thing here, got used to it by now

 

[bulwnkl]

rumor has it, exxon gas contains a lot more ethanol than other brands such as shell and chevron... that's why it's so cheap!

yes, ethanol does cause the car (not designed for it) to idle bad and have bad gas mileage

This is all misinformation. All automobile engines sold in the USA must tolerate up to 10% ethanol, and it's been that way for over 25 years. Direct personal experience with the 5 in particular shows absolutely no difference whatsoever between pure gasoline and up to 10% ethanol in terms of mpg, drivability, idle quality, or any other measure of performance.

It is worth noting, however, that "Exxon" gasoline is among if not the lowest-gravity (lowest density) gasoline in the country at this point. It is accordingly the lowest energy content. Personally, given the shenanigans XOM has been pulling with their Mobil1 oil in recent years, I won't willingly give them my money for any of their products. Fortunately for me, the refinery that supplies over 90% of the gas stations in this part of the country is a Conoco-Phillips refinery.

 

[TheMAN]

tolerate and *works* with it are totally different things

fuel system seals and rubbers have been 10% ethanol tolerant for years for sure, but ECU tuning on many cars 10 years and older (and maybe some newer) generally don't account for running this s*** though... I tell you what... my beater corolla idles funny and had preignition problems (everything was checked out good and it was decarboned too) until I used colder plugs on them... why? because ethanol's energy content is lower and it burns hotter despite that fact

good for you that your 5 runs fine with it, but on my protege, I get BETTER gas mileage when I fill up in BFE (which either has no ethanol or much less) than here in the city
again, lower energy content from ethanol, and the ECU doesn't know you're running it so its running the engine a tad rich

 

[OilGuy]

The closest refinery (or terminal) usually supplies much of the gas for an entire region - regardless of brand. The additive package may change. This may throw a monkey wrench into some brand bias out there.

 

[Nova2009Mazda5]

Ethanol discussion is interesting, and a factor that hadn't occurred to me. I've seen a few stations with stickers on the pumps stating a 10% ethanol content in the fuel. I wonder if stations are required to post signs like that, or is ethanol so common now that it is just assumed everywhere? Is there any way to know, other than asking a station attendant who probably has no clue?

As far as gasoline quality, I seem to recall reading that the gas found in any given geographic region all comes from the same refineries and therefore the only differences from one station to another are the brand-specific additives and the condition of the station's equipment (storage tanks, etc). In my case, it really is striking how much better my 5 rides after going to a different station.

 

[Rocket]

Direct personal experience with the 5 in particular shows absolutely no difference whatsoever between pure gasoline and up to 10% ethanol in terms of mpg, drivability, idle quality, or any other measure of performance.

My experience is very different. My state was ethanol free for the first 50,000 miles of ownership. I averaged 25 mpg. Once all of the fuel around here was placarded "contains 10% or less ethanol" my mileage dropped to 22.5 mpg on average. I keep detailed records, there is no doubt in my mind that the E10 caused my mpg to drop by 10%.

 

[thaxman]

Rocket, sounds about right. They say E10 is good for a power drop/consumption increase.
Around here, we get different formulations for summer & winter & supposedly pure gasoline in the off seasons. But the rural areas are supposed to get all pure. Funny, my last trip from Yuma, AZ yielded 21.5 mpg HIGHWAY!!!
With mpg like that, I would suppose its all ethanol.

 

[bulwnkl]

until I used colder plugs on them... why? because ethanol's energy content is lower and it burns hotter despite that fact

Wrong again. Flame temps are lower with ethanol than gasoline. Flame propagation rate is higher with alcohol than gasoline, though, as is expansion ratio. This is part of the reason that the lower energy content in alcohol does not result in the lower mileage that everyone likes to calculate for themselves. In addition, ethanol does a radically better job of keeping the fuel system and even cylinders clean vs. pure gasoline.

The various different (re)formulated fuels result in lots of different vehicular behaviors. It's not the ethanol itself that lowers mileage, and frankly a quick calculation based on some folks' numbers will show that the ethanol would have to be energy-free water or something in order to be solely responsible for the mpg differences one sees. It's just silly to suppose that 10% of some non-gasoline additive resulted in 10% mpg decline. The additive would have to have zero energy to accomplish that feat.

 

[bulwnkl]

The closest refinery (or terminal) usually supplies much of the gas for an entire region - regardless of brand. The additive package may change. This may throw a monkey wrench into some brand bias out there.

Exactly. That's why I said I'm glad we get C-P fuel for most of our fuel here.

 

[TheMAN]

Wrong again. Flame temps are lower with ethanol than gasoline. Flame propagation rate is higher with alcohol than gasoline, though, as is expansion ratio. This is part of the reason that the lower energy content in alcohol does not result in the lower mileage that everyone likes to calculate for themselves. In addition, ethanol does a radically better job of keeping the fuel system and even cylinders clean vs. pure gasoline.

The various different (re)formulated fuels result in lots of different vehicular behaviors. It's not the ethanol itself that lowers mileage, and frankly a quick calculation based on some folks' numbers will show that the ethanol would have to be energy-free water or something in order to be solely responsible for the mpg differences one sees. It's just silly to suppose that 10% of some non-gasoline additive resulted in 10% mpg decline. The additive would have to have zero energy to accomplish that feat.

if you say so...

http://www.streetdirectory.com/travel_guide/48858/mileage_and_fuel/alternative_energy_ethanol.html
http://thehill.com/business--lobby/...s-turn-to-washington-for-help-2008-12-02.html
http://www.associatedcontent.com/article/290874/using_ethanol_blended_gasoline_does.html?cat=27
http://www.dailygazette.com/news/2008/apr/24/0424_ehthanol/

 

[coolmazda5]

allrighty, I guess the original Q has been answered already and the rest is getting off the track so let's just close it