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Old 01-24-2013, 10:55 PM   #1
Scooby Newbie
Member#: 336417
Join Date: Oct 2012
Chapter/Region: NWIC
Location: Idaho
2008 STi

Default Noob Gas Question

Hi all,

My fiance has a 2013 Impreza Base and when it is cold (10F or less ish) it will take a while to start and when it does it lugs for a second and then idles normal and all is well. Normally I would not even care but this thing has 4k miles on it...

Anyways guy at the dealer says something about in the winter he tells people to run a higher octane to avoid this. This goes against what I thought I knew about octane, that higher = harder to ignite....or is that not the case - is it JUST harder to SELF ignite under pressure???

I put some 89 in instead of 86 last fill up and it does seem to start a lot better, but just wondering if this is voodoo?

Could also be that winter gas here is just crap, not sure...

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Old 01-24-2013, 11:05 PM   #2
Scooby Newbie
Member#: 333423
Join Date: Sep 2012
Chapter/Region: NWIC
Location: Oregon
2012 WRX Hatch
Dark Gray Metallic


I think you are correct about higher octane gasoline being harder to "ignite" but 89 shouldn't be an issue. No matter, I wouldn't think that your newer car should struggle to crank right up unless your battery is too weak/dying.
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Old 01-24-2013, 11:25 PM   #3
AWD Freak
Scooby Specialist
Member#: 262593
Join Date: Oct 2010
Chapter/Region: MWSOC

This might help. I found it just searching the web


Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates. High levels of detergent can be found in Top Tier Detergent Gasolines. These gasolines exceed the U.S. EPA's minimum requirement for detergent content.[citation needed] The specification for Top Tier Detergent Gasolines was developed by four automakers: GM, Honda, Toyota and BMW. According to the bulletin, the minimal EPA requirement is not sufficient to keep engines clean.[10] Typical detergents include alkylamines and alkyl phosphates at the level of 50-100 ppm.[4]

And for the top tier locations, you can go to http://en.m.wikipedia.org/wiki/Top_T...rgent_Gasoline
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Old 01-24-2013, 11:29 PM   #4
Scooby Specialist
Member#: 340009
Join Date: Dec 2012
Chapter/Region: SWIC
Location: Arizona
2007 STi


In the mornings my car would take a bit longer to crank over when its cold, I just started letting the gauges cycle before actually starting and it greatly reduces the amount of cranks to turn over.
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Old 01-25-2013, 07:27 PM   #5
Scooby Newbie
Member#: 142128
Join Date: Feb 2007
Location: Brooklyn, NY
2012 WRX


Im not sure if this applies to the Impreza base, but on WRX/STI, they do require (not recommend) 91 octane and up. It was in the manual and when I bought my subaru, they specifically told me to use 91 and up.

Try looking through your manual or calling the dealership and see what it requires. Also, 91 octane will treat your car alot better than 86 or 89.
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Old 01-25-2013, 07:53 PM   #6
Mr Wrex
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Member#: 332887
Join Date: Sep 2012
Chapter/Region: Tri-State
Location: Orange County, NY
2012 WRX stage 2+
DGM (sedan)


Gas evaporates slower in the cold and oil is thicker as well. On top of that, the chemical reaction occurring in your battery is slower, which gives the engine less power to start with. I'm not too sure about the whole "higher octane in winter" bit, so I decided to look it up:
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Old 01-25-2013, 09:03 PM   #7
Scooby Specialist
Member#: 220971
Join Date: Aug 2009
Chapter/Region: South East
Location: West, NC
2002 WRX 221K Mi.
Original Motor and Turbo


Buy 0% ethanol fuel and there wont be a problem. Subarus are not designed to run on any more than 10% ethanol. They will, but is says in the manual:

Not sure if you had a typo, but the MIN octange rating is 87 AKI or 90 RON For all Base 2.0I and 2.5I engines ,depending on what your area measures by.

Section 7-3
Many gasolines are now blended with
materials called oxygenates. Use of these
fuels can also help keep the air cleaner.
Oxygenated blend fuels, such as MTBE
(Methyl Tertiary Butyl ether) or ethanol
(ethyl or grain alcohol) may be used in
your vehicle, but should contain no more
than 15% MTBE or 10% ethanol for the

proper operation of your SUBARU.

If undesirable driveability problems are
experienced and you suspect they may be
fuel related, try a different brand of gasoline
before seeking service at your SUBARU dealer.

The detergents and higher octane espically in colder temps when the air is denser, seems to counter act the effects of ethanol a bit.

So if you are getting 86 octane you are below the MIN spec for fuel.
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Old 01-25-2013, 11:49 PM   #8
Scooby Newbie
Member#: 336417
Join Date: Oct 2012
Chapter/Region: NWIC
Location: Idaho
2008 STi


Hrm I did not think about the ethanol, or the detergents. This has been on Chevron gas, which probably is on the higher end in terms of detergent containment...

Also I should have been more clear, the crankover rate is not an issue/slower than normal, it just cranks WAY longer and when it did start it was idle really low/lug for a second or two.

It has only been two days so there is no science behind this claim but it has started better now so far with the 89 in it.


Thanks I actually did not look, but seeing how we have ****ty low octane gas in this part of the country anyways it makes sense as our regular gas is 86 not 87 lol


The higher octane recommend in the turbo versions of these cars relates directly to them being turboed, it is not necessarily better to run 91 in a NA car (unless it has high compression ratios, etc that would also require it to have a higher octane fuel)
In my STi's manual it actually says to run 93 and you CAN run 91 lol Stupid S. Idaho we only have 91
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Old 01-26-2013, 02:33 AM   #9
happs subi
Scooby Specialist
Member#: 200288
Join Date: Jan 2009
Chapter/Region: BAIC
Location: East Bay Area, CA
2002 Impreza WRX
World Rally Blue


There is surprisingly great info in this thread.

There could be a number of reasons why your car takes longer to start in the morning. I think the best thing to do would be to get it checked out by your dealer while you still have a warranty. New cars should start right up.

As far as the quality of your gas.. Something might be wrong. Maybe your local gas station has not been properly storing the gasoline, or its been sitting for awhile.
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Old 01-26-2013, 02:37 AM   #10
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Member#: 273906
Join Date: Feb 2011
Chapter/Region: NESIC
Location: Romance
Meow Gravel Grinder
Cadence @ 120 HowBow dah


I read something somewhere on this site about the new Imprezas having batteries with very weak cold cranking amps. I have a stock Subaru battery in my '99 Impreza (400 cca maybe? Just a guess) and it puts out power very slow in these near zero temps. The Duralast Gold (800cca?) in my Outback is much better, but it still gives the starter noticeable less juice.
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Old 01-26-2013, 09:18 AM   #11
Scooby Specialist
Member#: 287534
Join Date: Jul 2011

Octane and detergent have very little to do with cold starting. The RVP (Reid Vapor Pressure) rating of the fuel affects cold starting more than anything else. Basically, it's the ability of the fuel to vaporize at lower temps. That's why you hear of "winter blend" and "summer blend" fuels. Winter blend fuels will have a higher RVP than a summer blend.
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