I have a 2008 Honda CBR 150.

The sticker on the petrol tank says "91".

I'm guessing 91 fuel in 2008 maybe had a different composition to the "current day" 91. Am I wrong?

If the garage doesn't have 91, can I fill it with anything else that won't damage the engine, or make it run rough?

(Edit - oh, I see now, the small print says E10 is OK).

Personally would run 95 in it.

papa had a black '09

150 ceeber.

put 55Kkm on her

all over Thai, Laos , Cambo.

Lovely fast bike.

[redline is 11.5]

Finally gave her to a deserving lad 3 years ago.

In favor of a CB150 w/ ABS.

Can still ride it if I want.

5 5

Keep an eye on the oil if

you running her hard.

 

The sticker on my Wave says 91 our local bike mechanic says use 95, which I have done, now 160000 km later, still going strong.

It will not make the engine run rough, days of engines pinking due to wrong fuel have well gone.

Normally the figures of 91 and E10 indicate the minimum calorific value of fuel allowed by design of the engine.  Any higher value ( say 95)  “ normally “ is allowed however the ECU ( Engine control unit) might take some time to adjust to this. That is why when you constantly change fuels, the ECU is being given a workout and may experience some rough running for a little while as the ECU adapts to different fuel regimes.   As someone said, the higher the calorific value fuel, the better the engine runs, normally is the case.

Gasohol 95 (E10)

That's it.

Most pumps do not have another choice anyway.

95 is the measure for knock resistance. Simply better than 91.

Some pumps still have 91 but price advantage is marginal.

Since years they announced phasing out 91 which would simplify logistics but no.

Ok, I stand corrected.

On 11/2/2025 at 5:59 PM, Marvo said:

I'm guessing 91 fuel in 2008 maybe had a different composition to the "current day" 91. Am I wrong?

 

E10 91 was introduced in about 2007. So will be OK. But as other have said E10 95 is only a few satang more expensive I'd go with that. 

13 hours ago, Phantom57 said:

, the higher the calorific value fuel, the better the engine runs,

their caloric value is the same

1 hour ago, papa al said:

their caloric value is the same

[91 vs 95]

RON 95 is not better than 91, it's a total misconception..., best to use the correct RON suitable for your engine... 

 

When it says 91 on the tank, use that, when it says 95 use that, and so on... 

 

Of course modern ECU adjust everything to cope using 95 instead of 91, but it will have zero effect on performance or better running of the engine..., can do a quick Web search and find out for yourself...

 

5 hours ago, Agusts said:

RON 95 is not better than 91, it's a total misconception..., best to use the correct RON suitable for your engine... 

 

When it says 91 on the tank, use that, when it says 95 use that, and so on... 

 

Of course modern ECU adjust everything to cope using 95 instead of 91, but it will have zero effect on performance or better running of the engine..., can do a quick Web search and find out for yourself...

 

RON marked is a minimum, so 95 works fine in 91 spec bike.

Higher Octanes often contain additives for 

upper cylinder lubrication

or vs deposits.

Especially Shell.

19 hours ago, papa al said:

RON marked is a minimum, so 95 works fine in 91 spec bike.

Higher Octanes often contain additives for 

upper cylinder lubrication

or vs deposits.

Especially Shell.

 

Shell might add their own extra stuff, no idea..., but PTT and other local gas stations have no such additives..., the 95 only contains an additive so it can stand higher pressure..., low pressure engines don't need it...!

 

1 hour ago, Agusts said:

 

Shell might add their own extra stuff, no idea..., but PTT and other local gas stations have no such additives..., the 95 only contains an additive so it can stand higher pressure..., low pressure engines don't need it...!

 

You don't know about Shell,

but do know about PTT.

Source.?

papa ver curious.

On 11/6/2025 at 5:05 PM, Agusts said:

 

Shell might add their own extra stuff, no idea..., but PTT and other local gas stations have no such additives...

This exemplifies  the Dunnig-Kruger effect.:

Dumb/ ignorant people usually believe

they they are smart/ informed.

--------------------------------------------->

Thai PTT 95 octane gasoline (often called PTT Blue Gasoline 95 or PTT Blue Gasohol 95, depending on ethanol content) includes several fuel additives designed to improve performance, cleanliness, and efficiency.

🔹 Typical Additives in PTT 95 Octane Gasoline

While the exact proprietary formulation isn’t public, PTT discloses the general categories:

1. Detergent / Deposit Control Additives

   • Prevent carbon and gum buildup on fuel injectors and intake valves.

   • Help maintain engine performance and reduce emissions.

2. Corrosion Inhibitors

   • Protect metal parts in the fuel system from rust or corrosion, especially important in ethanol-blended fuels.

3. Antioxidants

   • Prevent fuel oxidation and gum formation during storage.

4. Demulsifiers

   • Help separate water from fuel to prevent phase separation and poor combustion.

5. Metal Deactivators

   • Neutralize trace metals that can catalyze fuel oxidation.

6. Friction Modifiers (in premium grades)

   • Reduce internal engine friction for slightly better fuel economy.

7. Octane Boosters

   • Maintain the 95 RON rating (such as certain aromatic hydrocarbons or oxygenates like ethanol).

🔹 Variants

• PTT Blue Gasoline 95 → Pure gasoline (no ethanol).

• PTT Blue Gasohol 95 → Contains 10% ethanol (E10 blend).

  • Uses similar additives but includes extra corrosion and water control agents due to ethanol content.

In 2008, 91 was probably noticeably cheaper than 95, and why they emphasize using, and just marketing.   Especially since they also state E10 will work.

 

Now 95 is basically the same price as 91, because most programmed to use 91 now, go figure.   E10 (good luck finding) & E85 is no longer that much less, and kpL will be less, or was my experience w/E85.

 

Test both and see how the performance & kpL are, and go with the best, as prices are too similar to worry about.

 

9 hours ago, papa al said:

This exemplifies  the Dunnig-Kruger effect.:

Dumb/ ignorant people usually believe

they they are smart/ informed.

--------------------------------------------->

Thai PTT 95 octane gasoline (often called PTT Blue Gasoline 95 or PTT Blue Gasohol 95, depending on ethanol content) includes several fuel additives designed to improve performance, cleanliness, and efficiency.

🔹 Typical Additives in PTT 95 Octane Gasoline

While the exact proprietary formulation isn’t public, PTT discloses the general categories:

1. Detergent / Deposit Control Additives

   • Prevent carbon and gum buildup on fuel injectors and intake valves.

   • Help maintain engine performance and reduce emissions.

2. Corrosion Inhibitors

   • Protect metal parts in the fuel system from rust or corrosion, especially important in ethanol-blended fuels.

3. Antioxidants

   • Prevent fuel oxidation and gum formation during storage.

4. Demulsifiers

   • Help separate water from fuel to prevent phase separation and poor combustion.

5. Metal Deactivators

   • Neutralize trace metals that can catalyze fuel oxidation.

6. Friction Modifiers (in premium grades)

   • Reduce internal engine friction for slightly better fuel economy.

7. Octane Boosters

   • Maintain the 95 RON rating (such as certain aromatic hydrocarbons or oxygenates like ethanol).

🔹 Variants

• PTT Blue Gasoline 95 → Pure gasoline (no ethanol).

• PTT Blue Gasohol 95 → Contains 10% ethanol (E10 blend).

  • Uses similar additives but includes extra corrosion and water control agents due to ethanol content.

 

Sorry, but this does not say one word if 91 version does not have all these additives, please find and add the list for that too..., then you get the thumbs up...!  (also the source / link so I can check...)

On 11/8/2025 at 5:07 PM, Agusts said:

 

Sorry, but this does not say one word if 91 version does not have all these additives, please find and add the list for that too..., then you get the thumbs up...!  (also the source / link so I can check...)

no

This is the latest prices below , I think the extra additives mentioned is for the "Premium" brand of 95 which is closer to 40 baht a liter, all oil companies have that type...(it makes the engine go so much faster, smoother and cleaner even after a few million kilometers ..!😜)... 

 

I appeal to your sense of logic and common sense, do you think a company adds all that expensive additives to normal 95 and not the 91 and sell it for 3.7 satang more...!?!? (that's less than 0.5 baht)... 🤔, do you think they are really, really that stupid, or extremely generous...? (Thais...! 😉) 

 

If you think so then no problem, go ahead and use 95 for the feel good factor, that's what life is all about after all..., I use 91 on my low pressure engine (10.5/1) scooter and dump it for a new one after 50k km anyway, in case engine is so dirty... 😅, I don't need to go 200kph by using 95 instead of 91 anyway... (it does 150kph with 91 now, that's enough..) 😎

My summer job while an engineering student was in the testing laboratory at a local refinery.  One of my duties was to test the final mixtures of the various fuels sold.  I had to run gasoline samples through the 'knock engine'.  It was fitted with a mechanism that allowed changing the compression ratio.  We would adjust the compression until pre-ignition (knocking) occurred.  Then we could calculate the precise octane rating.

 

An engine using 95 gas will run without knocking at higher compression rates compared to 91 gas.  Apart from that there is very little difference between those two fuels.  Burn the one the manufacturer recommends.  Don't waste your money on a higher octane than needed.

 

Just for kicks.... which situation requires the higher octane:

a) driving through the mountains

b) cruising beside the ocean beaches

??

 

14 hours ago, gamb00ler said:

 

Just for kicks.... which situation requires the higher octane:

a) driving through the mountains

b) cruising beside the ocean beaches

??

Lower octane is needed at altitude...

[higher density altitude.]

11 hours ago, papa al said:

Lower octane is needed at altitude...

[higher density altitude.]

temp and barometric pressure come into it.

And normally aspirated,

turbos change everything.

You want to buy the top shelf stuff.

 

On 11/12/2025 at 9:04 AM, impulse said:

You want to buy the top shelf stuff.

 

Good money earner, these bottles work out at almost 50 baht/liter.

22 minutes ago, kickstart said:

Good money earner, these bottles work out at almost 50 baht/liter.

I used to think they were selling whisky on the sly. I bought a bottle one day but the bloke wouldn't let me take it home. 

My guts haven't been the same since.🙃🙃

21 hours ago, Lucky Bones said:

I used to think they were selling whisky on the sly. I bought a bottle one day but the bloke wouldn't let me take it home. 

My guts haven't been the same since.🙃🙃

why.?