Gasoline: 91 Or 95?

[danone]

my car runs on 91.

once, because the 91 had run out at the station, I went for 95. got quite better mileage and acceleration.

since then I mostly get 95, even though the manual says the engine is made for 91.

anyone does the same?

and ruined the engine?

[tigerbeer]

our civic can do 91, 95 is better. its better for the engine and would not ruin anything. nothing to worry about.

[backflip]

The octane number is a measurement of anti-knock properties, and has nothing to do with gas mileage. If your can is designed to run on 91 octane gas, running it on 95 octane fuel will not damage your vehicle. The other way around, you could cause damage. There are two octane numbers, research and motor - and one is inevitably higher. Accordingly, in the US, the oil companies would advertise the higher number. The US government passed a law that the advertised octane would be calculated as: (research + motor)/2. I do not know if the companies in Thailand use the same formula.

[Crossy]

my car runs on 91.

once, because the 91 had run out at the station, I went for 95. got quite better mileage and acceleration.

since then I mostly get 95, even though the manual says the engine is made for 91.

anyone does the same?

and ruined the engine?

Well it won't hurt the engine unless you're using Gasohol 95 and your car's fuel system is not compatible.

I'm intregued by your assertion that you get better economy and acceleration using 95, is this just a subjective observation or can you back it up with figures??

Certainly, when I went to school (a while ago) there were lots of advertising campaigns saying that putting 4-star in a vehicle designed for 2-star was just throwing money away.

[fxm88]

Buying the expensive stuff -- especially when your car doesn't need it -- is a great way to gain face at the petrol station!

Has anyone seen 100+ octane (racing fuel) for sale? It's awesome (and expensive)!

Edited January 24, 2007 by fxm88

[danone]

fxm88: thats cute, bashing someone who uses less gasoline for a better mileage. but you dont get even this one i guess.

i drive every week bangkok - hua hin and back.

leaving bangkok with a full tank of 91, i get back to bangkok when about the empty tank light switches on.

leaving bangkok with a full tank of 95, there is ample gasoline left arriving in bangkok.

95 seems to give me a better mileage of about 10 percent with clearly improved acceleration.

actually i always get 95 gasohol.

am driving a crv 02, 2.0 lts

[elkangorito]

I wonder what ever happened to those water injection kits you used to be able to buy? They were great...improved power & therefore fuel economy. Also helps to help the 'insides' clean.

[fxm88]

fxm88: thats cute, bashing someone who uses less gasoline for a better mileage. but you dont get even this one i guess.

Since plenty of good advice is available thru a simple Google search I thought maybe you were asking on this forum because you were looking for something specific to Thailand. If I misunderstood, I do apologize. Here are some links but I'm sure you could find many, many more:

20 ways you waste money on your car

...

Premium gas instead of regular. Buy the cheapest gasoline that doesn’t make your car engine knock. All octane does is prevent knock; a grade higher than the maker of your car recommends is not a “treat.”

...

Source: http://articles.moneycentral.msn.com/Savin...yOnYourCar.aspx

GASOLINE OCTANE FACTS and MYTHS

Minnesota Department of Commerce

...

Octane Myths

• High octane gasoline improves mileage.

In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve

mileage. If switching to high octane gasoline does improve mileage, you might find that your engine, or its

control systems, need repair.

• High octane gasoline gives quicker starting.

No, it doesn’t.

• High octane gasoline increases power.

If your car is designed to run on 87 octane gasoline, you shouldn’t notice any more power on high octane

gasoline. Again, if it does make a noticeable difference, your engine, or the engine’s electronic control

systems, may need repair.

...

Source: http://www.state.mn.us/mn/externalDocs/Com...OctaneFacts.pdf

SEPTEMBER 17, 1997

FTC FINALIZES EXXON SETTLEMENT;

Nationwide Consumer Education Campaign Will Inform Consumers

That Regular Gas, Not High Octane, Is Right For Most Cars

...

"Many consumers buy high octane gas believing it is a 'treat' or a 'treatment' for their cars," said Jodie Bernstein, Director of the FTC's Bureau of Consumer Protection. "But it's the consumers getting the treatment, not the cars. Most cars don't need and won't benefit from hi-test gas, so paying extra for premium gas is wasting money," she said. "Now Exxon will join the FTC and the American Automobile Association to get the word out to consumers: Unless your owner's manual calls for high octane fuel or your engine is knocking, there's no reason to pay for premium gasoline," she said. "This is a precedent-setting law enforcement remedy that will save American consumers money."

...

Source: http://www.ftc.gov/opa/1997/09/exxon.htm

...

What's the right octane level for your car?

Check your owner's manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

How can you tell if you're using the right octane level? Listen to your car's engine. If it doesn't knock when you use the recommended octane, you're using the right grade of gasoline.

Will higher octane gasoline clean your engine better?

As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

...

Source: http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

I couldn't find any good info specific to Thailand (indeed, all of those are US specific) but I did find one article in the Pattaya Mail (from 1998) that touches on it e.g. it states "The rather ironic thing in this whole debate is that the petrol you buy at the pump isn’t 95 or 91 RON anyway - it’s 97 and 92! Confused? You will be soon!" The article is at http://www.pattayamail.com/253/features.htm#hd6 and a reader's response is at http://www.pattayamail.com/255/letters.htm#hd3

Good lcuk!

[danone]

thanks for the follow ups fxm88, appreciate.

thats exactly why i'm posting the question.

nobody recommends the higher octane.

but in real world tests i get an improved performance.

i'm driving on 95 since over a year.

went twice back to 91. nope, not the same!

[Crossy]

How about a little thought experiment?

Many, many years ago when I did my own car maintenance (when cars had contact points and carburettors) one thing we learned was that the ideal ignition timing for maximum performance was having it advanced to such a point that the engine knocked then retarding ever so slightly. The distributor had a nifty vernier screw to make the job easier.

So, modern engine management systems working in a similar way, advancing the timing until the knock sensors trigger, then retarding it just a smidge. This being a real-time operation, constantly adjusting the timing and fuel mixture for best performance.

Now let's increase the fuel octane rating.

I know that my old cars would let me advance quite a bit more before knocking if I put 4-star in the tank rather than my regular 2-star. If I ran it like this on 4-star the car definately went better.

Our fancy engine management systems have more variables than just the timing, they adjust the mixture (and also the valve timing in VVT engines) as well as monitoring the RPM, air flow and exhaust composition.

Maybe, just maybe, that's why our OP is seeing a performance improvement using 95, the engine is actually sensing the better fuel and adjusting itself to use it.

OK people.... flames on......

[danone]

intersting crossy, tks.

may there be any longterm harm - such as clogging - in using another than recommended octane?

or do the variables, as you describe then, adjust accordingly?

***

another test would be if some of you 91ers would give it a try with a 95-fill.

Edited January 24, 2007 by danone

[fxm88]

Maybe, just maybe, that's why our OP is seeing a performance improvement using 95, the engine is actually sensing the better fuel and adjusting itself to use it.

This seems like the more likely explanation (see above post for more):

...

• High octane gasoline improves mileage.

In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve

mileage. If switching to high octane gasoline does improve mileage, you might find that your engine, or its

control systems, need repair.

...

[Crossy]

If switching to high octane gasoline does improve mileage, you might find that your engine, or its

control systems, need repair.

Yeah, I remember reading that, BUT, assuming the mileage on 91 is reasonable (ie it's not drinking it) I don't really what can be broken that makes things BETTER

For most of my engineering career when stuff goes wrong things usually get worse!!

[Sojourner]

All of the newer cars have black boxes that, among other things, register pre-ignition via a sensor in the exhaust header. Since pre-ignition (knock) is an irregular burn of the gasoline and is more of an explosion than a burn, it can damage the engine. The black box will retard the ignition slightly to compensate for the knocking. This in turn reduces the performance of the engine as the ignition is firing later than it should for optimum performance. In years past octane was boosted by adding tetraethyl-lead to the gasoline. This additive simply slowed the burning of the gasoline, called a flame-path, across the piston and prevented knock. Amaco (USA) started using a different process to raise the octane number to allow the muscle cars of days-gone-by to use engines with 10-11 to 1 compression without knocking. That process is used by most all of the majors today. Gasoline is gasoline and burns at a certain BTU rate. Gasoline is also a commodity that is traded, sold, in bulk around the world. It's virtually the same no matter where it's refined. It's only the additives that make the difference when it comes to things like knock, emissions or keeping injectors clean. Are the local refiners using proper QC when it comes to their two different grades of gasoline? That's the question. I use Caltex because they are adding techroline to their gasoline and also guaranteeing their product is not tampered with before it goes into the service station's storage tanks. Techroline keeps injectors clean by not allowing sulfur to accumulate in the fuel delivery system. I still remember the days of Sunoco 260. Is that dating myself?

[HDRIDER]

Drive diesel cars

[stingray]

Diesel Cars? Not smooth enought, and underpowered

[PETERTHEEATER]

Drive diesel cars

Diesels? They are for trucks, not cars. Death rattle noises at start and idle. They all seem to need turbochargers to get any reasonable power out of them and cooling the ###### things after high speed driving accounts for the lines of shale oil burners rattling away on unoccupied idle that I have to put up with when I make a relief stop at a highway petrol station.

Signed - A happy petrol engine user.

[danone]

test drove diesels as well, but man, what a different world.

am more than willing now to pay the extra for gasoline. even wonder now why people try to save money with diesel when you have to bear with all the multiple discomforts (such as noise in the first place).

[Sojourner]

Here's an interesting explaination of premium vs regular gasoline and how it relates to performance and cost.

Posted octane numbers on gasoline pumps are a result of testing fuel performance under laboratory and actual operating conditions. The higher the octane rating on fuel the less volatile (evaporative qualities) and the slower the fuel burns. Higher octane fuel contains more POTENTIAL energy but requires the higher heat generated by higher compression ratio engines to properly condition the fuel to RELEASE that higher potential energy. In the refining process, fewer gallons of higher octane fuels are yielded from a barrel of raw crude.

[Thanh-BKK]

This is a motor mechanic writing (certified professional).

Gasoline with 95 octane burns at a higher temperature than gasoline with 91 octane. Also it needs longer to combust fully, hence the advanced ignition timing for 95 usage. It can also withstand higher pressure without igniting by itself, which is why high-performance engines need to run on higher octane fuel.

However using 95 in an engine that is made for 91 has no downsides apart from the higher cost of the actual gasoline. Older engines can be set for either fuel by setting the ignition timing properly (more or less advanced), modern engines usually sense the fuel quality automatically and adjust the ignition timing by themselves.

Since 95 burns at higher temperatures, obviously it releases more energy. This in turn makes the engine produce more power out of the same amount of gasoline, hence - better mileage. It is no secret but well known fact that a 91 engine, running on 95, runs significally more economic.

For the same reason (more energy released in combustion) the "better acceleration" is felt.

The other way round, using 91 in an engine specified for 95, can have negative side effects such as "knocking" (gasoline igniting before the spark because of self-ignition, caused by high pressure that comes along with high temperature) as well as poor performance - 91 yields less power than 95! On engines which sense the fuel quality, there will be no knocking since the ignition will be set accordingly by the on-board controller/computer, however the power will still be lower and the engine will guzzle quite a lot more gas!

My Volvo 460 can use, according to the manual, anything from 76 octane upwards. Normally i drive it with Gasohol 95 (95 octane is recommended by the manufacturer) but once i used 91 just to test. It had a considerably lower acceleration power and i got around 60 km less out of the tankful than when driving on 95! Which is a lot, considered that i normally get no more than 350 km out of a tank anyway with that gas guzzler. There is no difference in either power or mileage between using gasohol 95 or pure gasoline 95, also i did not notice any difference in either when using different brands of gas.

In my motorbike, a Yamaha RXZ, i use 91 octane all the time. Here i feel large differences in the mileages depending on what BRAND of gas i use - with "Caltex Silver" i get around 200 kilometers out of a tankful, while on "Petronas" it is only around 180 kilometers and with "Shell" even less - around 160. Also the engine runs a lot smoother and at lower idle on "Caltex Silver" than on any of the others, so they must have some additive in that stuff that's specially good for two-stroke engines. This bike is of course carburetor-aspirated and has no fuel sensors, so it's got to be the fuel itself that makes the differences.

Kind regards....

Thanh

[tom yum goong]

There is no difference in either power or mileage between using gasohol 95 or pure gasoline 95

are you sure?

from my own experiences and from talking to many other car owners, i find gasohol gives considerably lower mileage (around 10%) and less power.

i tried using gasohol but stopped after finding that it was less economical (and less powerful) than both regular 91 and 95, despite the cheaper cost per litre.

[undercover]

91s not worth the liquid its manufactured from, I get much better performance + better milage from 95,

Also my old motorbike, 25/30 kicks to get it started in the morning on 91, 3/4 kicks on 95, I couldent afford to go back on 91 I just don't have the stamina for it.

[danone]

excellent, finally we're getting somewhere, tks for your detailed input thanh.

but i do agree with the 2nd gasohol observation. gasohol gives my car too quite less stamina and therefore less mileage, so its not worth the few satang you save.

looks like i'm only feeding my car 95 from now on! used 95 gasohol so far.

[lingling]

actually i always get 95 gasohol.

am driving a crv 02, 2.0 lts

Honda don't recommend gasohol for 02s...

http://www.honda.com.au/wps/wcm/connect/Ho...Owners/Ethanol/

[danone]

actually i always get 95 gasohol.

am driving a crv 02, 2.0 lts

Honda don't recommend gasohol for 02s...

http://www.honda.com.au/wps/wcm/connect/Ho...Owners/Ethanol/

tks for that link. makes all sense now, no more gasohol in my engine!

here's another interesting link - this site claims that with higher octane you may get an additional 10 percent hp (which is about my experience):

http://www.tegger.com/hondafaq/premiumgas.html

[Sojourner]

This from Cycle World, January 2007 edition.

Quote: Some vehicles are being produced as "flex-fuel" users, which means their fuel systems are able to adjust fuel delivery enough to prevent lean operation when large amounts of alcohol are present. Such vehicles are clearly identified as such in their manufacturer literature. The best advise so far is to look in your owner's manual. Several I have examined recently say that up to 10-percent ethanol may be used.

Alcohol contains significantly less energy per gallon than does gasoline. This is because it is already partially burned which is to say that it has an OH group attached to it, making some of the hydrogen in the molecule unavailable for combustion. For this reason, mixtures of gasoline and alcohol contain reduced energy-that is, they make engines run lean. Engines with oxygen sensors can compensate to some degree for this leanness, but flex-fuel engines can compensate to a larger degree.

This issue of alcohol-blending fuels is a propaganda battle. Farmers naturally see the economic opportunity, and "greens" sense a plus for renewable fuels. But since alcohol contains only about 60 percent as much energy per gallon as gasoline, and since producing it requires considerable expenditure of energy to boot, the question of whether it is worth doing has no clear answer.

We're all going to be petroleum engineers before this is over.

[Thanh-BKK]

This from Cycle World, January 2007 edition.

Quote: Some vehicles are being produced as "flex-fuel" users, which means their fuel systems are able to adjust fuel delivery enough to prevent lean operation when large amounts of alcohol are present. Such vehicles are clearly identified as such in their manufacturer literature. The best advise so far is to look in your owner's manual. Several I have examined recently say that up to 10-percent ethanol may be used.

Alcohol contains significantly less energy per gallon than does gasoline. This is because it is already partially burned which is to say that it has an OH group attached to it, making some of the hydrogen in the molecule unavailable for combustion. For this reason, mixtures of gasoline and alcohol contain reduced energy-that is, they make engines run lean. Engines with oxygen sensors can compensate to some degree for this leanness, but flex-fuel engines can compensate to a larger degree.

This issue of alcohol-blending fuels is a propaganda battle. Farmers naturally see the economic opportunity, and "greens" sense a plus for renewable fuels. But since alcohol contains only about 60 percent as much energy per gallon as gasoline, and since producing it requires considerable expenditure of energy to boot, the question of whether it is worth doing has no clear answer.

We're all going to be petroleum engineers before this is over.

Best for the "greens" and others who just want to stay as ecological as they can while still using a car: Drive a Diesel and use cold-pressed 100% vegetable oil. They sold that stuff 7 years ago in Germany already as an alternative fuel, most Diesel engines need no modifications at all to run on palm oil or soybean oil, it may smell a little "funky" but heck, no matter what comes thru the exhaust with that fuel, it is exactly what nature took to produce it, you CAN'T drive cleaner. And it's got to be cheaper too as all you need to do is to press it and filter it, done, no refining/blending needed.

I wonder why they don't have it in Thailand..... here they only start talking about a "bio-Diesel" which will be ordinary Diesel blended with veggie oil......... what a waste of time, sell veggie oil straight from the pump to go eco!

Kind regards......

Thanh

[CHdiver]

Best for the "greens" and others who just want to stay as ecological as they can while still using a car: Drive a Diesel and use cold-pressed 100% vegetable oil. They sold that stuff 7 years ago in Germany already as an alternative fuel, most Diesel engines need no modifications at all to run on palm oil or soybean oil, it may smell a little "funky" but heck, no matter what comes thru the exhaust with that fuel, it is exactly what nature took to produce it, you CAN'T drive cleaner. And it's got to be cheaper too as all you need to do is to press it and filter it, done, no refining/blending needed.

I wonder why they don't have it in Thailand..... here they only start talking about a "bio-Diesel" which will be ordinary Diesel blended with veggie oil......... what a waste of time, sell veggie oil straight from the pump to go eco!

Kind regards......

Thanh

Now; if you compare the Diesel Price in Germany/Europe to Thailand; that will give you the answer. For Biodiesel buy from the Gasolinestations; you mostly don't need moditications. You will find out about that by reading the Usermanual. But many People in Europe just went to the next Supermarket (like Aldi, Lidl) and bought there the cheapest Oil. In Europe you mostly need a heater for the Oil, because of the colder Temperature. Should not be a Problem in Thailand. But as the Diesel is much cheaper, I dont see a advantage here.

Back to the Discussion about 91/95 Gasoline: I drive a Nouvo. I can drive this Scooter with 91, but I experienced that the Engine runs smoother with 95 Gasoline. But not more Power ore less consumption of gasoline. I changed back from time to time, exerienced more vibrations. Now I go all the time for 95.