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Difference between 91 and 95 fuel


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14 hours ago, RickG16 said:

have I got the wrong end of the stick?

All fuels have a shelf life. 

 

Depends what you want to know. 

If you car handbook says you can use 91 then no worries to use 95 is OK but if a price difference then you are wasting dosh. 

 

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17 minutes ago, johng said:

As I understand it, the difference between 91 and 95  is the octane rating,  engines with a higher compression ratio ( higher performance) require a higher octane rated fuel to help prevent "knocking"  AKA  the fuel igniting too early when it is compressed in the cylinder.

 

If the engine has a lower compression ratio then lower octane fuel can be used,using a higher octane fuel in a lower compression engine will not in itself increase the performance of that engine but using a low octane fuel in a high compression engine can result in damage therefore In modern engines the fuel management system can compensate for low octane fuel and associated "knocking"  which will lead to a decrease in performance whilst using that fuel.

 

E20 has 20 percent ethanol   which I believe has a lower energy density than straight petrol

(less Km's /L)  ethanol is also a higher octane fuel   E85 is supposed to be good for tuned up turbo engines. 

Your trying to understand too much. 😂

The ECU's in cars/trucks these days adjust and have knocked sensors. 

Many petrol engines these days and diesels are designed to run on different fuels. 

e.g. say Honda City can run on E85. 

My Isuzu truck can run on B20. 

 

The consensus is still with what fuel is available to you in your area and not switch about with fuels. 

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9 minutes ago, KhunBENQ said:

As the name says, E20 has 20% ethanol and what is not in the name: it is at least 95 octane (knock strength).

91 should have vanished from the market since long but they again stretched it for whatever reason.

As I never use 91 I can only tell you that I need about 0.3l/100km more with E20 compared to 95. About 7.5 l/100km compared to 7.2l/100km.

Currently it hardly pays to use E20 over 95 (only 1.5 Baht difference).

(sorry you have to do US/UK math yourself, I am hardcore metric).

 

Don't spend a thought on using 91 with a modern motor (high compression ratio).

You just loose power. 91 is for lawn movers and scooters at best. But why go for it with this small price difference?

Even son refused to use it for his brush cutter.

Village "tank stop" has no 91 barrel.

 

91 octane has been abolished in most of Europe for more than 10 years.

I have to disagree with some of what you say. 

The fact though is if your car engine is designed to run on 91 there is not a problem. 

 

I run my 28 years old Fireblade motorbike on 91 E10 with no problem at all because it can. 

If I want go faster,  mechanical engine parts alterations or a nitro kit fitted would be the only thing that would make a difference. 

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Every engine is optimized for a specific octane number fuel.

So if 91 is good enough, then running with 95 will not give your any benefits.

Running with cheaper 91 in an engine made for 95, will cause engine knocking/pinging, which in the end can damage your engine.

 

But TS is actually not way off in his thinking.

Generally speaking, an engine with higher compression ratio, requiring higher octane number fuel is actually more efficient, more powerful and will provide a better fuel economy compared to a lower compression ratio engine running on a lower octane number fuel.

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21 minutes ago, Montnoveau said:

Every engine is optimized for a specific octane number fuel.

So if 91 is good enough, then running with 95 will not give your any benefits.

Running with cheaper 91 in an engine made for 95, will cause engine knocking/pinging, which in the end can damage your engine.

 

But TS is actually not way off in his thinking.

Generally speaking, an engine with higher compression ratio, requiring higher octane number fuel is actually more efficient, more powerful and will provide a better fuel economy compared to a lower compression ratio engine running on a lower octane number fuel.

Low compression !!!! Can you explain why my Honda Supersport bike will run on 91 E10.

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30 minutes ago, Kwasaki said:

Low compression !!!! Can you explain why my Honda Supersport bike will run on 91 E10.

What is the compression ratio of the engine ?  

My Honda 150cc 2 smokes Liquid cooled workshop manual says it has a compression ratio of 6.8:1  and to use 91 octane or higher fuel, my 4 stroke DOHC  air cooled Suzuki 150cc workshop manual says its 10.2 :1   recommends 91 or higher octane too maybe it could benefit from 95  according to the chart below.. over the years I've tried 91 and 95 in both and noticed no difference in either machine.

 

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse4.mm.bing.net%2Fth%3Fid%3DOIP.Any7mvpiQ1JHSsJGYH-HRQAAAA%26pid%3DApi&f=1

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2 minutes ago, johng said:

What is the compression ratio of the engine ?  

My Honda 150cc 2 smokes Liquid cooled workshop manual says it has a compression ratio of 6.8:1  and to use 91 octane or higher fuel, my 4 stroke DOHC  air cooled Suzuki 150cc workshop manual says its 10.2 :1   recommends 91 or higher octane too maybe it could benefit from 95  according to the chart below.. over the years I've tried 91 and 95 in both and noticed no difference in either machine.

 

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse4.mm.bing.net%2Fth%3Fid%3DOIP.Any7mvpiQ1JHSsJGYH-HRQAAAA%26pid%3DApi&f=1

6.8 :1, hmm, is it supercharged....

I tried 110 octane in my 10.25:1 fun car to protect it when using N2O on the strip.

 

Normally I used 98, there was no difference in the track times with the 110.

 

Putting 95 in a 91 car will make little or no difference, putting 91 in a 95 car may make a difference if the knock sensors pick up knock and the onboard CPU adjusts the ignition timing.

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2 minutes ago, johng said:

What is the compression ratio of the engine ?  

My Honda 150cc 2 smokes Liquid cooled workshop manual says it has a compression ratio of 6.8:1  and to use 91 octane or higher fuel, my 4 stroke DOHC  air cooled Suzuki 150cc workshop manual says its 10.2 :1   recommends 91 or higher octane too maybe it could benefit from 95  according to the chart below.. over the years I've tried 91 and 95 in both and noticed no difference in either machine.

 

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse4.mm.bing.net%2Fth%3Fid%3DOIP.Any7mvpiQ1JHSsJGYH-HRQAAAA%26pid%3DApi&f=1

You have answered your own question.

As it says typical requirements may vary.

My engine is a 28 year old Carb engine it can adjust from 87 to 98.

There to much drama about fuel use,  it easy to set up engine and know what regular fuel to use. 

With engine nowadays with fuel injectors and ECU's they can adjust themselves.

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10 minutes ago, transam said:

6.8 :1, hmm, is it supercharged....

No its just a bog standard 2 stroke motorbike   no knock sensors,oxygen or airflow sensors catalytic converter, programmable ecu's   ... just a good old fashioned carburettor 91 fuel and some 2t oil thrown in for good measure 😋

 

16 minutes ago, Kwasaki said:

My engine is a 28 year old Carb engine it can adjust from 87 to 98.

How does it adjust ??

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1 minute ago, johng said:

No its just a bog standard 2 stroke motorbike   no knock sensors,oxygen or airflow sensors catalytic converter, programmable ecu's   ... just a good old fashioned carburettor 91 fuel and some 2t oil thrown in for good measure 😋

 

How does it adjust ??

By the carburetors.

Air and fuel mix.

Say like on your 2 stroke you will do a oil and fuel mix. 

I hate 2 strokes. 😂😂

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A few months ago I read where someone else asked the same question. The answer was each vehicle was manufactured to burn a certain octane fuel. Uses a higher could damage your vehicle. As mentioned, that was a few months ago and I don't know where that article is. I did a search this morning and found that mostly there isn't really any benefit if you use a higher octane. 

1. A car that does not require premium gas may not have any added benefits:
Using premium gas in a regular car will cost you more with almost no added benefits. The Federal Trade Commission says that using a high-octane gasoline rather than a recommended one will offer almost no benefits. It will not make your engine perform better or faster.

3. Cars with Turbochargers or heavier cars need premium 

If your car is a regular one that does not have turbochargers or is not a heavy engine car, using a premium gas will only waste your money. As the cars that are heavy or have turbochargers have higher compression ratios, they knock without premium fuel. Therefore, using premium in older cars is necessary rather than regular cars.

There are no visible side effects or benefits of using premium gas in a regular gas car. However, if you want to use premium gas in your regular car, ask automobile experts about this. People put premium gas in a regular gas car for better car performance and handling, but in very rare case this is the outcome. With appropriate maintenance tips and regular check-up for your car, you can certainly improve its performance and longevity to multiple folds.

So do what is right for your car.

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3 hours ago, KhunBENQ said:

(...)

You just loose power. 91 is for lawn movers and scooters at best. But why go for it with this small price difference?

(..,)

 

I run my scooter on 95.

The price difference is so negligible, at least for me doing 2 to 3 full tanks per month, that I stopped asking myself the question years ago.

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55 minutes ago, Kwasaki said:

I hate 2 strokes. 😂😂

Used to go to the airport, get a drum of 115/145 AvGas for my Hi and H2 Kwackers

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13 hours ago, scubascuba3 said:

the prices are very close now about 20-30 Satang so if in doubt just get 95

If its a rental scooter get 91.

 

If its you own, get 95.

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1 hour ago, seedy said:

Used to go to the airport, get a drum of 115/145 AvGas for my Hi and H2 Kwackers

Dumb thing to do in Thailand, didn't you have a handbook, you were wasting your time. 

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1 hour ago, Kwasaki said:

Dumb thing to do in Thailand, didn't you have a handbook, you were wasting your time. 

Not much stock on them - forks, front wheel, front half of the frame.

 

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22 hours ago, RickG16 said:

OK thanks. But everything else aside, which lasts longer?

Depends on your driving habits. No way to tell as each car's reaction to different octane fuels will be slightly different.

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