91 And 95 Petrol

[Neeranam]

Can I alternate with the different types?

Mazda 323, 8 years old.

[kayo]

On my old honda dream, i used either one.

[lampard10]

On a high performance engine you might get a touch of 'pinking' but I doubt it. 91 octane...........just think of it as putting ice in your beer. Or more like it the difference between an 8 or 12 year old whisky.

[higgy88]

I don't really understand why you would want to alternate between the two. Your owners manual would identify which fuel you should use. If you need 95 and you use 91, this could possibly cause some serious engine damage. If your car can run perfectly well on 91 and you use 95, then you are just wasting your money, and fuel is expensive enough as it is.

[JAS21]

Can I alternate with the different types?

Mazda 323, 8 years old.

We have a 323 varient, a LANTIS..always use 91..the red pump...of course you can use 95. You can mix it in any quantity that you want..you wont get any benefit by using 95.

See my comments on lpg/nav. The Mazda had a big boot..we can still get two large golf bags in. We have the 47Ltr tank.

If it 'pinks' on 91 then you maybe have a timing problem..go to the Mazda dealer.

[Axel]

Not sure, if I do understand all. Your car needs 95, which will be no longer available in Thailand.

So what do you use?

[PeaceBlondie]

Not sure, if I do understand all. Your car needs 95, which will be no longer available in Thailand.

So what do you use?

That's almost a different problem. Isn't somebody saying the Mazda 323 probably runs fine on 91, so it doesn't need 95? I can't believe that my Honda CBR150 (that's for sale) has a compression ratio well over 10:1 and runs without pinging/predetonating on 91, as the manual recommends.

But if your manual says 95, are they going to phase out the straight petrol, and only provide ethanol, which could damage your engine?

[moonoi]

Can I alternate with the different types?

Mazda 323, 8 years old.

I just had a quick look on the Mazda forums for 323 Astina and its seems that it requires a minimum of Premium/95.

Couldn't find anything about whether you can use gasohol without any issues though. really need to check with a Mazda dealer/ specialist to be sure.

[Neeranam]

I'm going to change to 91 as it is cheaper.

Wha t is pinking?

[moonoi]

I'm going to change to 91 as it is cheaper.

Wha t is pinking?

If you want to damage your engine thats upto you, but why ask for our advice if your just going to ignore it anyway?

Pinking (Knocking or Pinging) - Technically detonation: in internal combustion engines occurs when fuel/air mixture in the cylinder has been ignited by the spark plug and the smooth burning is interrupted by the unburned mixture in the combustion chamber exploding before the flame front can reach it. Combusting stops suddenly, because of the explosion, before the optimum moment of the four-stroke cycle. The resulting shockwave reverberates in the combustion chamber and pressures increase catastrophically, creating a characteristic metallic "pinging" sound.

The fuel/air mixture is normally ignited slightly before the point of maximum compression to allow a small time for the flame-front of the burning fuel to expand throughout the mixture so that maximum pressure occurs at the optimum point. The flame-front moves at roughly 33.5 m/second (110 feet/second) during normal combustion. It is only when the remaining unburned mixture is heated and pressurized by the advancing flame front for a certain length of time that the detonation occurs. It is caused by an instantaneous ignition of the remaining fuel/air mixture in the form of an explosion. The cylinder pressure rises dramatically beyond design limits. If allowed to persist detonation will damage or destroy engine parts.

Can be prevented by:

The use of a fuel with higher octane rating

The addition of octane-increasing "lead," isooctane, or other fuel additives.

Reduction of cylinder pressure by increasing the engine revolutions (lower gear), decreasing the manifold pressure (throttle opening) or reducing the load on the engine, or any combination.

Reduction of charge (in-cylinder) temperatures (such as through cooling, water injection or compression ratio reduction).

Retardation of spark plug ignition.

Improved combustion chamber design that concentrates mixture near the spark plug and generates high turbulence to promote fast even burning.

Use of a spark plug of colder heat range in cases where the spark plug insulator has become a source of pre-ignition leading to detonation.

Correct ignition timing is essential for optimum engine performance and fuel efficiency. Modern automotive and small-boat engines have sensors that can detect knock and retard (delay) the ignition (spark plug firing) to prevent it, allowing engines to safely use petrol of below-design octane rating, with the consequence of reduced maximum power output and efficiency.

A knock sensor consists of a small piezoelectric microphone, on the engine block, connected to the engine's ECU. Spectral analysis is used to detect the trademark frequency produced by detonation at various RPM. When detonation is detected the ignition timing is retarded, reducing the knocking and protecting the engine.

[higgy88]

[tom yum goong]

...

Can be prevented by:

The addition of octane-increasing "lead," isooctane, or other fuel additives.

...

is this the best option for people with cars which need 95 octane and can't run on gasohol 95?

[Crossy]

Can be prevented by:

The addition of octane-increasing "lead," isooctane, or other fuel additives.

is this the best option for people with cars which need 95 octane and can't run on gasohol 95?

The additives are fine, if you can get them. But why not let the oil companies put them in for you, a much more closely controlled process than bunging a tin of something in the tank. Ah that's 95 octane petrol!

Oil companies have spent billions taking LEAD out of petrol

[Eman]

On a high performance engine you might get a touch of 'pinking' but I doubt it. 91 octane...........just think of it as putting ice in your beer. Or more like it the difference between an 8 or 12 year old whisky.

One reason to "mix" might be to save money...

Your Mazda may run perfectly well on slightly lower octane fuel than is specified in the owner's manual (and also might not, you need to experiment a bit).

Say, if you discover your car runs acceptably well on 93, you could mix 1/3, 2/3 of the 91 and 95 octane fuels to get 93 and save a small amount of money.