What Octane Do You Prefer?

[Dr_Snooz]

Higher octane does nothing at all to keep your engine cleaner.

Um, yes it does. They put more detergent in the higher grades.

[Vanilla Sky]

Um, yes it does. They put more detergent in the higher grades.

That's not due to the higher octane rating, that's due to extra detergents. Not all brands have the added detergents in the higher grades, either. I try to use Chevron here in town, and Shell everywhere I can get it, so I'm using pretty good fuel no matter the grade.

Unless things changed, E15 is required to be in a separate tank with a separate pump. Not all vehicles can run on E15 without fuel system issues.

[Pnem3]

I use 87. I always thought and heard that from a technical standpoint, octane performance and mileage were tied to compression. Higher compression engines produce more power from higher octane gas because they have more compression. I don't see how our cars can take advantage of that since their compression isn't high enough to need more than 87 octane.

[obdriver6]

I use 87, anything else is a waste of money on these cars, unless you're turboed or have an engine with high compression, as long as you stay away from the cheap places (Billy Bo Bob Gas Station) and go with the good gas (Shell, Chevron, ect.) you should be fine just remember you get what you payed for.

[lostforawhile]

remember in some of the higher grades, they don't add corn, it depends on the station, etc,

[frantik]

i always use 87 never had any problems.. Rotten Robbie or Arco for me

[gp02a0083]

Unless things changed, E15 is required to be in a separate tank with a separate pump. Not all vehicles can run on E15 without fuel system issues.

yes our cars will probably have a slight problem with the E15, i can say right now without even putting that stuff in my hatch that you will get junk gas mileage.

anything after 12.5%-13% ETOH (ethanol) causes a sever drop in power, only benefit to having the higher amounts of ethanol is lower combustion temperatures that lead to a cooler running engine. re-timing the ignition would most likely be required to accept E15.

i had a discussion with BISImoto about this when they stated using E85 gave a 4% power increase due to the fuel being used, then they went and said that ethanol has more energy per unit than gas. Needless to say they didn't know they were talking to a chemist

lost is correct as far as the detergents/additives , everyone has a different blend that they use, overall there really similar. My friend used to work for sunoco and told me a lot about the blends they use. Just also keep in mind that gasoline is a mixture of chemicals, many of which you can find in the paint supply section of any store.

[Oldblueaccord]

Ill say this BTU is only part of the equation. Remember 93 octane had less BTU then 87 does but MOST cars get better mileage with higher octane fuel. High power levels and gas mileage don't always go hand in hand in fact I would guess almost never.


wp

[Oldblueaccord]

wow, your commute sounds just like mine!
I have heard a lot of opininos and data supported debates on this topic. It seems to vary a LOT between models.
As for latley I use 87 in everything but I did put in 93 in the B20 LX last month and that gas seemed to last a lot longer. That could have been my driving style changed to see how many mpg I could squeeze in general. The 87 I filled up with in the same car last week seems to be going down faster but I won't know pure data till next week.
Big news today is the E15 we're about to get, well believe we already have been getting it wiith out being told.
Will we all have to be using owner poured additives to hold this stuff back from separating and corroding our fuel systems? Could be a rise in sales of that stuff, stockholders.

Yeah I need to do a highway run and see if I can get a 34 I used to get on long trips. Age of the car, 250 cc injectors,205/50 tires probably don't help.

To be fair also I have the timing advanced some and I can run it all the way advanced without any ping I can hear where as with 89 octane I could hear some ping between throttle on shifts.

wp

[2drSE-i]

yes our cars will probably have a slight problem with the E15, i can say right now without even putting that stuff in my hatch that you will get junk gas mileage.

anything after 12.5%-13% ETOH (ethanol) causes a sever drop in power, only benefit to having the higher amounts of ethanol is lower combustion temperatures that lead to a cooler running engine. re-timing the ignition would most likely be required to accept E15.

i had a discussion with BISImoto about this when they stated using E85 gave a 4% power increase due to the fuel being used, then they went and said that ethanol has more energy per unit than gas. Needless to say they didn't know they were talking to a chemist

lost is correct as far as the detergents/additives , everyone has a different blend that they use, overall there really similar. My friend used to work for sunoco and told me a lot about the blends they use. Just also keep in mind that gasoline is a mixture of chemicals, many of which you can find in the paint supply section of any store.

You will get better power running E85, but you will be burning through it much faster, correct? Ethanol burns cleaner, but also hotter and faster.


If I could get E85 here in OK (without going on our AFB or driving an hour out of my way) I would already be converted and tuned. This gas price nonsense is ridiculous.

[DBMaster]

This is as good an article as any I have read. I became interested after a trip to Colorado during which I noticed that regular was 85 octane.

http://www.squidoo.com/regular_or_premium

As far as E85 goes, it is a known fact that even flex fuel vehicles lose power and fuel economy when they run on E85. About the only thing it's good for is as a "cheap" fuel for high compression or heavily boosted engines.

It appears that the oil companies' marketing efforts are still yielding great results!

[gp02a0083]

You will get better power running E85, but you will be burning through it much faster, correct? Ethanol burns cleaner, but also hotter and faster.

if you are comparing E85 to gas ( no ethanol), or even E10, gallon for gallon you would not get the same energy output with a higher amount of ethanol. Ethanol burns slower than gasoline and burns cooler. This is the primary advantage of ethanol, it will allow the engine to run at a lower operating temperature. This is why they use ethanol and methanol in racing.

Also, and this is what really pisses me off when people say ethanol is soo much better, is the fact that you are basically burning off 1/2 a water molecule ( the OH group in the alcohol) in the combustion reaction. Water takes up a frigging butt load of energy in the combustion, meaning you would have to put more energy into the system to get even a fraction out. Another strong point that is a down fall of ethanol is its hygroscopic characteristic, water is extremely soluble in alcohol ( at least the low carbon chain alcohols). let it sit for a few days, i guarantee that the car will run really bad as it is also trying to burn water.

As far as he rate of consumption, this would be independent issue. This would require remapping the ecu / fuel management system to achieve the proper air /fuel ratio. This would depend on the fuel delivery, ignition timing and compression.

here is a pdf with a chart showing the differences between ethanol , methanol and gasoline

http://iqlearningsystems.com/ethanol...cteristics.pdf

[2drSE-i]

if you are comparing E85 to gas ( no ethanol), or even E10, gallon for gallon you would not get the same energy output with a higher amount of ethanol. Ethanol burns slower than gasoline and burns cooler. This is the primary advantage of ethanol, it will allow the engine to run at a lower operating temperature. This is why they use ethanol and methanol in racing.

http://iqlearningsystems.com/ethanol...cteristics.pdf

guess i had it assbackwards then lol

[gp02a0083]

no that fine , its a mistake many people make.

[Oldblueaccord]

Amazing I even make it to work everyday.

I remember in 1994 when I changed from r12 to 134a Pep boys told me my compressor would lock up and fall off and that it would turn everything inside to green goo and purple jelly. These are direct quotes the guy sadly still is the manager there I just bought a brake part off him last week.



wp

[wh1skea]

I voted 87. I've tried running 93 octane in my hatch and had WORSE gas mileage than I did with the 87 octane. I was very surprised by the results.

[DBMaster]

^^Don't be surprised. You results are consistent with the science. If you use higher "octane" gas than what you need to prevent knocking you SHOULD see lower gas mileage. I put octane in quotes because pump octane ratings are different than the actual chemical content.

[MessyHonda]

^^Don't be surprised. You results are consistent with the science. If you use higher "octane" gas than what you need to prevent knocking you SHOULD see lower gas mileage. I put octane in quotes because pump octane ratings are different than the actual chemical content.

yeah alot of people dont understand that a higher grade just means its a more stable fuel for high compression, high reving and turbo cars. lower grade means gas burns up faster or it takes less to make it spark

[charliekuney]

I just filled up with Shell Premium Plus (whatever their highest octane is). My car runs quieter and seems to be getting better gas mileage, although I haven't been delivering as much...

[Oldblueaccord]

Amazing I even make it to work everyday.

I remember in 1994 when I changed from r12 to 134a Pep boys told me my compressor would lock up and fall off and that it would turn everything inside to green goo and purple jelly. These are direct quotes the guy sadly still is the manager there I just bought a brake part off him last week.



wp

Well after this last post I was pissed that gas was up over $3.85 as oil per barrel had dropped sub 100$ so when I went to fill up I only put 3 gallons in. Enough to get home and 2 ways to work. I did this about 4 times never putting more than 4 gallons of E-10 or straight gas as it is here. Beginning of the week I filled the tank again with e-10(87 octane) and filled it last night. 339 miles to 11.6 gallons. 29 mpg. Thats down one mpg from my following 30,30 the previous calculations with 30% ethanol.

Ill be honest It could have been 349 miles I zeroed the odometer and did the math later and my memory has not been as sharp.

Only theory I have is that the car runs a little rich anyway and the mixed gas runs a little leaner,burns better, and I can get about the same mileage. Truthfully I feel no performance difference.

wp

[Australian 86]

i run 98 (ron) which i think equates to 93...
i recently heard of a study (admittedly with newer cars) testing out which petrol got the best k's per $. Supposedly the 98 got the best rating by the tiniest smidgen... not that i really care, just as long as they are about the same.
My logic behind getting the best petrol is;
potentially better k's per $.
fraction more power.
fraction better for the engine.

I think that if this is correct it makes sense to use the better petrol...

I just filled up with shell v-power today and ill see how i go...

[Rebel4x4]

i run 87 i just drove 187 miles to NC stopped at Shell when i got there an it took 5.4 gallons to fill back up. Roughly 35mpg. I Only use Shell gasoline though and they are always pretty close to the Blow Schmo guys. OH YEAH! Octane maybe doesnt neccesarily effect mpg but maybe quality of gas. I knew this old man who owned a gas station in the little town i grew up in and he told me that the "93" gas was no more than the "87" and "89" mixed together with just a tad more detergents not even enough to worry about

[import racer]

I use 89 unless gas price goes down then 93.And I always buy shell,we don't have ethanol around here.

[DBMaster]

This is not totally on topic, but I noticed in the years since I quit using mid grade that the cost differential between the grades has increased to at least 20 cents per gallon. It was 10 cents back when I was using 89 octane. Just another reason not to use higher octane than what you need. If you are using a "top tier" gasoline brand there is nothing to be gained by spending extra money for "detergent." We're not talking about Tide or Cascade here. It is just, perhaps, a slightly higher proportion of different crude distillates (solvents). Top tier gas will keep engines free of deposits, period, in all grades. As I said much earlier in this thread, it's amazing how effective oil company marketing has been. Much like the vaunted 3,000 mile oil change it's an interesting lot of psychological warm fuzzies. Unless you are comparing fuel economy and power output under controlled conditions your evidence is anecdotal at best. When auto publications test these things they do not use commercial gas pumps and the car's odometer. They use calibrated instrumentation. Also, in the real world the drive you took yesterday is different from today. Even if it was exactly the same route and traffic density and you drove it EXACTLY the same way there still could be temperature, humidity, and barometric pressure differences that can all affect fuel economy.

[lostforawhile]

100 Low lead