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Old 11-21-2012, 11:04 AM   #1
Pickler
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Default winter gas is killing me

i used toget 23.5 mpg overall mostly city in summer. now the same route i can get as low as 19mpg if im not careful. any other northern subaru na drivers suffering from this in winter?
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Last edited by Pickler; 11-28-2012 at 05:41 PM.
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Old 11-21-2012, 11:14 AM   #2
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Pretty much what I see in the Boston area. Not quite as dramatic of a difference as that, but it does go down a measurable 1-2mpg.
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Old 11-21-2012, 11:33 AM   #3
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I do have a WRX currently, but I've seen a rather dramatic drop since the introduction of winter gas this year too. I normally get 20/21 getting to work and it's been a good 17/18 now... sometimes I can stretch it to 19.

In my previous two NA subies, I'd see a similar 2-3 MPG drop. Just check your tires for inflation since that's in your hands. The other portion is just do due the gas and possibly letting the car idle while warming up.

I do notice that since the car takes longer to warm up, even when driving it, the ECU will be dumping more gas into the engine than if it was summer and it warmed up quick. All this adds up to a reduction in gas mileage in the colder months.
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Old 11-21-2012, 01:46 PM   #4
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Don't forget, winter time = colder/denser air that the car has to push out of the way while driving.
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Old 11-21-2012, 03:11 PM   #5
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i believe the denser air wont make a dramatic change below 55mph (as i said i do only city driving). i have noticed that my gas gauge just drops over night when the car is sitting in the driveway. this is possibly because of deicers in there evaporating. so my gas literaly evaporates lol. once i go through half the tank then the mpg starts to improve...
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Old 11-21-2012, 03:28 PM   #6
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Unless I missed something summer/winter gas is only a difference in ethanol content. Since ethanol has a harder time evaporating, winter gas has less ethanol. If it was just this, you should see an INCREASE in MPG. Sure something else isn't going on?
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Old 11-21-2012, 04:33 PM   #7
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Originally Posted by Bacon117 View Post
Unless I missed something summer/winter gas is only a difference in ethanol content. Since ethanol has a harder time evaporating, winter gas has less ethanol. If it was just this, you should see an INCREASE in MPG. Sure something else isn't going on?

I think you have that backwards...

Pretty good read here:
http://zhome.com/ZCMnL/PICS/winterGas/winterGas.html

Quote:
"Another major property in [reformulated winter gasoline] is the use of oxygen-bearing ether compounds like MTBE, ETBE (ethyl tertiary butyl ether) and ethanol. It's like pouring liquid oxygen into the combustion chamber. The engine doesn't have to draw the oxygen in because it's already available in the fuel."

As specified by state law, reformulated winter gas contains any number of lighter, lower-boiling-point hydrocarbons (butane, propane, etc.) that just so happen to have an excellent octane value. Added to this may be any number of oxygen-bearing ether compounds (MTBE, ETBE, ethanol) that improve emissions and also have a relatively high octane blending value. So what's all the bad hype for? Price, for one thing "It's actually more expensive to make reformulated winter gas than normal, summer fuel, ' says Thomas Hart. Lower fuel economy is another concern.
"The oxygen-bearing compounds displace fuel components, so it takes more fuel to get the job done. Normal gasoline has a stoichiometric ratio of 14.7:1, reformulated winter fuel runs between 14.3 and 14.4:1,"


Where has everyone been for the past ~10 years? I have recorded lower engine performance and MPG for at least that long.
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Old 11-21-2012, 04:59 PM   #8
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Interesting. I wonder if I can safely run 89 or even 87 in the winter due to the higher octane values of the additives?
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Old 11-21-2012, 05:52 PM   #9
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Interesting. I wonder if I can safely run 89 or even 87 in the winter due to the higher octane values of the additives?
I ran 89 all the time with my NA. I did see slightly better mileage, just enough to offset the cost. I did A LOT of tanks of data testing with this.

89 was best for my car. At least give it a shot. It did quiet the pinging down a bit, which is why I mainly used it. Gas mileage improved about 1 MPG, sometimes more. This was offset by the extra 10 cent price.
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Old 11-21-2012, 05:56 PM   #10
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My 07 2.5i is unhappy unless it has 93. Year round.
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Old 11-21-2012, 06:07 PM   #11
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I ran 89 all the time with my NA. I did see slightly better mileage, just enough to offset the cost. I did A LOT of tanks of data testing with this.

89 was best for my car. At least give it a shot. It did quiet the pinging down a bit, which is why I mainly used it. Gas mileage improved about 1 MPG, sometimes more. This was offset by the extra 10 cent price.
I currently have about 10.8:1 CR, so I've been running 92 to be safe.
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Old 11-21-2012, 08:38 PM   #12
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i have tried shell's 91 octane (ethanol free) without a tune (just ECU reset) and saw no difference aside from the car running slightly lean above 4000rpm. also using a gtech the 1/4mi times were also exactly the same. CBC also did an experiment with running shell vpower in chevy cruze but it actually resulted in nothing but increased emissions.

http://www.cbc.ca/news/canada/story/...emium-gas.html
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Old 11-22-2012, 12:50 PM   #13
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well that definitely explains the drop in gas mileage i've seen in my 07 2.5i
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Old 11-22-2012, 01:35 PM   #14
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Originally Posted by Pickler View Post
i believe the denser air wont make a dramatic change below 55mph (as i said i do only city driving). i have noticed that my gas gauge just drops over night when the car is sitting in the driveway. this is possibly because of deicers in there evaporating. so my gas literaly evaporates lol. once i go through half the tank then the mpg starts to improve...

air density will have an effect regardless of speed. The increase in air density from 20 degrees celcius to 0 degrees celcius is 7.3% therefore it will take roughly 7% more fuel to keep the AFR's the same assuming nothing else changes.

Personally I would stay away from any ethanol fuels, unless you are running one of those tunes that requires it.

To sum up ethanol theory quickly; ethanol contains Oxygen in its chemical formula. Therefore when combusting an equal amounts of non-ethanol blended and ethanol blended gasoline the latter will give you a lean reading at the 02 sensor, therefore the ecu will compensate with fuel trims by increasing the amount of fuel supplied to the cylinders to try to correct for what it thinks is a lean condition resulting in poorer gas mileage (also add in the lower energy effect as well).

Flex fuel vehicles as far as I know are really the only (factory) vehicles that can effectively use ethanol blended gasoline as they are able to measure the SG of the fuel they are running.

Last edited by J-hop; 11-22-2012 at 01:47 PM.
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Old 11-22-2012, 02:02 PM   #15
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air density will have an effect regardless of speed. The increase in air density from 20 degrees celcius to 0 degrees celcius is 7.3% therefore it will take roughly 7% more fuel to keep the AFR's the same assuming nothing else changes.
This would have an effect if you didn't have a throttle adjusting the amount of air going into the engine. Provide a lower volume of air to the engine with the throttle and you need a less amount of fuel. Disregarding the extra force of pushing colder, denser air around the car, it essentially takes the same amount of force to drive the car in both cold and warm conditions.

As has already been said, the difference in mileage that you see is from pushing the colder, denser air around the car and from running richer for longer while the cats warms up. Colder fluids also increase the pumping force necessary to move the moving parts through them (motor oil, trans fluid, diff fluid, etc.).
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Old 11-22-2012, 10:24 PM   #16
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Originally Posted by ADaughen View Post
I think you have that backwards...

Pretty good read here:
http://zhome.com/ZCMnL/PICS/winterGas/winterGas.html





Where has everyone been for the past ~10 years? I have recorded lower engine performance and MPG for at least that long.
I don't have it backwards exactly. I admit, I'm not 100% sure about normal fuel, which can be up to E10 (10% ethanol). But E85 absolutely has a winter blend. E85 can vary from E22 up to E85. There is less ethanol content in "E85" in the winter, that I'm certain of (it's something a spark plug engineer deals with). I made an assumption that normal fuel, with up to 10% ethanol, follows the same trend.
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Old 11-23-2012, 03:40 PM   #17
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i don't think i was clear enough about ethanol. As i said i tried both ethanol free shell vpower and the 10% ethanol containing petro canada 87 octane and i saw no difference in mileage or power. The only difference was the car running slightly lean above 4000rpm with vpower (i think 11:1 vs 10.8:1 at 6000rpm). Also i have been running 10% ethanol 87 octane gas in summer time with no issues, scoring 33mpg highway and 24mpg city consistently. Now my problem is the winter gas, it just seems to evaporate in there. about 18mpg city and 26 highway. it seems i'm right, according to petro canada's website:

http://www.petro-canada.ca/en/wholesalefuel/318.aspx
Quote:
It (winter gas) evaporates more readily than summer gasoline for improved cold weather start-ups.
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Old 11-23-2012, 05:10 PM   #18
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Oh man... I thought it was just me! I'm getting 19.53 real mpgs...
I guess I'll try 89 and see if I can get to 21, but this is ridiculous. From 25 to 19.5 is crazy.
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Old 11-23-2012, 05:17 PM   #19
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Oh man... I thought it was just me! I'm getting 19.53 real mpgs...
I guess I'll try 89 and see if I can get to 21, but this is ridiculous. From 25 to 19.5 is crazy.
Me too. I went from 26-28 to 22-24MPGs.
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Old 11-23-2012, 06:10 PM   #20
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Oh man... I thought it was just me! I'm getting 19.53 real mpgs...
I guess I'll try 89 and see if I can get to 21, but this is ridiculous. From 25 to 19.5 is crazy.
wont make any difference unless you tune your engine for it. i tried 91 ethanol free 0% gains.
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Old 11-23-2012, 06:13 PM   #21
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Anddddd just saved me another 5$ thanks. In my pathfinder I actually netted better MPGs btwn 87 and 91.
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Old 11-25-2012, 02:49 PM   #22
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1 major problem we have in Jersey is that some of our gas stations just sell ****ty gas. Watch where you are getting your gas from places like shell and Raceway down here seem to be cheaper because of the quality of gas.

My MPG is usally at 25-27 winter and 20-23 in the summer, Not sure why either. But I found if I put prem in I usually hit the 27-29 mpg. Expirement with the levels of octane.
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Old 11-25-2012, 03:12 PM   #23
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If you run summer tires in the summer and winter tires in the winter, that will account for a big difference. We see a 4-5 mpg difference between a 255 star spec and a 215 snow tire.
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Old 11-25-2012, 03:49 PM   #24
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If you run summer tires in the summer and winter tires in the winter, that will account for a big difference. We see a 4-5 mpg difference between a 255 star spec and a 215 snow tire.
+1 exactly. Lots of variables change when the season gets colder. Coming from a Toronto, Canada perspective, I get the same seasonal dip in fuel economy but it's due to a variety of things (i.e. winter-tires, colder air, winter-gas, etc.). Gotta pay to play right?
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Old 11-25-2012, 04:02 PM   #25
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+1 exactly. Lots of variables change when the season gets colder. Coming from a Toronto, Canada perspective, I get the same seasonal dip in fuel economy but it's due to a variety of things (i.e. winter-tires, colder air, winter-gas, etc.). Gotta pay to play right?
^ yea i think this is a good summary. Add in stuff like running your heater all the time, defrost, time spent out of operating temp etc.

To be honest I don't know why some of you southerners complain. we hit -4 degrees F and lower for consistent periods over the winter. Gas mileage is the least of your concern when the temperature starts to dip below that and your hands are purple from scraping the ice of your windshield. You are lucky to get into operating temperature sometimes on the way to work
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