octane use for winter/summer

[Highroller]

Im partially new to this winter/summer fuel thing so i hope i can gain some knowledge from you guys.

i've tried to research some but i need reassurance. So allow me to get this correct, higher octane has a lower volatility. Lower volatility should be use in warmer weathers. Lower octane = higher volatility. Higher volatility should be used in colder weathers, am i correct? So what im actually asking is that is higher octane = lower volatility and lower octane is vice versa?

Regards,
Eric

 

[Highroller]

Sorry to post this thread, im dumbfounded like always. I found my answer in another forum. I was just looking for an answer as to if one should use lower octane in colder weather for easier startup (ive been using higher octane in the summer). Please ignore the statements above.
Moderator could you please delete this topic, thanks.

 

[CharBaby]

So tell us! What is your finding? Should we use lower octane in colder weather or what? This site is about sharing information. Don't hold back, give it up!

 

[Stooge]

Note that in colder weather, the air is denser and thus contains allittle more oxygen. This has the effect of leaning the mixture and could actually cause more preignition in some engines.

Both my V8 Tundra and Sequoia seem to "ping" more in the winter, although the motors seem to "rev happier." I always use 87 octane gas.

 

[JohnnyO]

I don't think the octane itself matters, but the blend of gas is different in different parts of the country at different times of the year (thank you, EPA). Some engines will ping on the oxygenated fuel (I had one) or generally run ________ on it (like everything I own now). I don't think its the temp so much as the gas itself.

 

[Highroller]

Well you asked for it... the general consensus is that you should use what your car is spec'ed for. SOME engines can take advantage of the higher octane. Other engines can be damaged from going to a higher octane.

For my particular case (my 06 nissan titan V8), i found that it's spec'ed for 87 but i can definitely take advantage of premium. The only times where i can take advantage of using premium is only during WOT on the upper RPM band or pulling heavy load conditions, like towing. There were dyno tests done by running 5 tanks of 87 and then dynoing it and then doing another 5 tanks of 93 and doing a dyno on it. Results showed 245 hp to a 254 hp increase. Others have said that the titan's ECU is similar to the Infiniti's QX56 ECU, which was told to run premium in their manauls. The nissan titan has a 9.8:1 compression ratio and 87 octane can be used for 9.9:1 or lower (or so i was told). I have the link from another titan forum for the results but i dont really know if i can post it since it's not a bitog sponsor. Thus, if anyone wants to know... ill be sticking with 87 mostly and in the warmer months on special occassions, ill be using 93 to get some power and clean out any dirty injectors from winter fuels. Gas is so complex and interesting, not to mention somewhat expensive for some...

Here are a couple of articles that i find interesting:
http://72.14.209.104/search?q=cache:k8gi...t=clnk&cd=2

http://72.14.209.104/search?q=cache:a0xp...t=clnk&cd=3

Here are some quotes that are interesting:
"Since high temperatures increase volatility, it is desirable to have a low volatility fuel for warm temperatures and a high volatility fuel for cold weather. The blends will be different for summer and winter fuels."

"However, the higher the octane, the lower the volatility, making it more difficult for the gas to compress with the air. This in turn can lead to problems starting your engine, as a car filled with gasoline of too high an octane will have trouble mixing with air."

Regards,
Eric

 

[ARB1977]

I was into the higher octane craze about two years ago. Since then 87 has been used. If its not recommended then go with the lower octane.

 

[RD400]

Yeah, basically use the lowest octane you can get away with. Some engine and ECU combos just can't take advantage of possible higher power output gains using higher octane fuels, while others can. FWIW, my motorcycle is spec'd for 90 Octane REGULAR. (It's old)

 

[mechtech2]

The winter/summer volatility is related to the 'Reid vapor pressure'. The gas companies change this regionally and seasonally. Octane has nothing to do with it. If your engine ingests cooler air in the winter, it may need less octane. Sometimes, even though it seems backwards, the cooler denser air will require an increase in octane, because of higher cylinder pressures.

 

[Highroller]

Ahh.. thanks for that info. mechtech. Id love to learn more.

 

[Tosh]

Quote:

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Thus, if anyone wants to know... ill be sticking with 87 mostly and in the warmer months on special occassions, ill be using 93 to get some power and clean out any dirty injectors from winter fuels. Gas is so complex and interesting

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Myth Patrol says: Let's not perpetuate the myth about higher octane fuels being any cleaner than regular.

 

[Rickey]

Quote:

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Quote:

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Thus, if anyone wants to know... ill be sticking with 87 mostly and in the warmer months on special occassions, ill be using 93 to get some power and clean out any dirty injectors from winter fuels. Gas is so complex and interesting

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Myth Patrol says: Let's not perpetuate the myth about higher octane fuels being any cleaner than regular.

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Ok just call me seargent of the myth patrol. Fact: most higher octaine fuels use aromatic hydrocarbons to achieve their higher octaine. Aromatic hydrocarbons have high solvency and therefore can clean up the entire fuel tract. Now as for the cleanliness of the fuel itself thats another matter alltogether. Regular or premium it makes no difference either can be loaded with trash and the octaine rating could care less. Rickey.

 

[Highroller]

If one were to use Shell Vpower 93 octane, wouldn't it clean better than the regular grade?

Higher octane, burns slower, therefore makes a more complete combustion... allowing less emissions.. im just quoting stuff out from the top of my head now...

Regards,
Eric

 

[doctorr]

Seems to be at least TWO different myths at work here....

Higher Octane = higher volatility (RVP)

Reid vapor pressure has zero to do with octane, end of story. Refineries use more aromatics components to boost the octane, and they are some of the heaviest components of gas. Butane also makes a nice cheap octane jump, if they can get away with it within the RVP specs, butane is obviously a very light addition to a blend. You can't predict anything from "volatility".

The other myth would be the "high octane burns slower" one.
The "octane" rating is detonation prevention, and beyond that, has very little to do with flame speed or peak cylinder pressure.
.
.
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doc

 

[Highroller]

From what you're saying, im just spilling out myths here... jeeez thank goodness for this site or else i'd be fooled into believing some myths about gasoline octane or what not..

Thanks,
Eric

 

[Primus]

Octane number has nothing common with volatility. Normally manufactures have to blend different gasolines depending on climate. Say, our national standard mentions 4 different blends. Gas conformity to outside temperatures depends on two parameteres (properties): Distillation Index and Vapor-Liquid Ratio.

Distillation Index indicates gas volatility at different temperatures or, to be exact, temperatures at which 10 %, 50 % and 90 % of fuel is vaporized.

First (T10) shows how easy will be cold startings and winter gas should have lower temperature than summer one. The second (T50) shows ability to vaporize during warm up and the third (T90) - ability to burn at operating temperatures.

Apparently your confusion comes from the fact that at lower temperatures the engine is less demanding on octane (same for high humidity), i.e. when cold and rains the engine is less pron to knocking.

 

[Highroller]

Yes, that was my confusion Primus, thanks for clarifying.

 

[OriginHacker21]

My grandpa (lifetime car mechanic) always told us to run a tank of 91 octane every 2-3 fillups because it will burn all the junk that 87 didn't get.

In my PRE-BITOG days I've read somewhere to use higher octane in colder weather and in hot weather - lower octane. I know in my dad's prop airplane - the engine kocks a lot more on startup in the cold weather than in the summer.

 

[Highroller]

what is a 'kocks'?
maybe it sounds lame but not trying to be funny either....

i was told to run premium every other planned fillups also to burn off anything left from the use of lower octane..

 

[cousincletus]

FWIW my 2001 Dodge Ram 1500, 3.9 V-6 with 5 speed manual transmission had a tendency to ping once the weather got cold. Never pinged in the summer, only in the winter. 89 octane would cure the problem. When the truck needed new sparkplugs I installed Autolite 3923's (colder plug) and that cured the problem. So now I can run 87 octane in the winter.