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Whether you've got a Tico or a Lexus, a Daelim or a Harley, this is the forum to discuss transport in Cambodia. Where to buy it, how much to pay and what to do when the wheels fall off.
AE86 Tip: ALWAYS use premium fuel on ANY car or truck (petrol of course) that you own.
This is a little bit of a recap on something I've written a while ago but can't find my post on it, but to recap, always run your car or truck with premium fuel REGARDLESS if it is stated as being able to run on regular. Reason being is because the regular fuel in Cambodia often does not meet the minimum octane requirement for more modern cars newer than the early 90's, so knock/pinking and possibly detonation can occur which results in decreased fuel mileage at best and damage to the internals of your engine at worst.
If you use premium, not only will your car be safe from any potential damage, but you will get better fuel mileage and will not end up spending extra money.
***End of summary***
The more detailed and geeky explanation why below.
Okay, three very important things you just need to know to understand why I say what I do.
1. All octane ratings (to the best of my knowledge) are RON octane numbers (research octane). If you are from the U.S. or Canada, forget the numbers you are used to, because they are NOT THE SAME as here. So 91 octane here does not equal 91 octane over there.
2. Most vehicles here are rated for the AKI (R/M+2) octane rating...which is NOT what Cambodia rates their fuels on.
3. RON & AKI (R/M+2) octane ratings DO NOT CORRELATE to one another.
Got it? No? That's okay, it's confusing.
So, what does this have to do with using premium or not?
I know often times people in the West hear about how premium fuel isn't required in vehicles unless specified (like the sticker above states), but for ease of things, just forget that bit of info. Cambodia's octane rating system is completely separate from the AKI (R/M+2) octane ratings the U.S. and Canada (Brasil too) are based on, so none of the numbers apply to what the manufacturers requirements are outlined under. So if the numbers don't apply, then how do we know what we can and can't use? Why not try regular?
Because while the numbers are not related, petrol is still petrol and is designed to be burned in our engines, and even though it's not a hard fast rule...I've found that when using regular in everyday cars, the fuel seemed to "act like" 84-85 octane fuel (U.S. Canada rating). "Normal" cars like a small Kia or Toyota Camry tend to knock on this fuel and get poor fuel economy on it, while motos, even relatively sophisticated ones do just fine, and if you think about it, it makes sense to do this since so many Cambodians use motos on an everyday basis. Why refine fuel more when it's not necessary for a massive chunk of the population?
However, this means that "normal" U.S. and Canadian market cars (which is what most of the cars are here) will not run properly on this type of fuel. So in a nutshell that is why I recommend premium.
Is there any downside to using regular or "street fuel" in a pinch?
Yes, but it's usually not catastrophic. Modern cars are designed to automatically compensate for different conditions, like hot low speed conditions in Cambodia, and can physically run and USUALLY avoid damaging then engine. The trade off is worse fuel economy. However, if your car isn't in the best mechanical condition, or one of it's systems is not correctly functioning, then you may end up causing damage to your engine.
If the regular fuel here is not good enough for "regular" cars, is the premium fuel good enough for cars that require premium?
I can't comment on all vehicles obviously, but I can say that I have a car that requires premium and generates a lot of heat (which makes prime condition for knocking). I've not had a problem with knock related to fuel except on hot days with the air conditioner on while sitting in traffic, then trying to pass a lorry quickly getting on boost. I've also had other cars that have required premium that did not have a problem on Cambodia's premium fuel.
Of course though, mechanical condition has a lot to do with things, so if you do have a problem with knocking/pinking, check to see if your car is okay first.
Is there any advantage to running premium in a moto?
Obviously if you have a "high performance" motorcycle then I recommend only using premium (my high compression Yamaha demands it and does not like regular), but for your average moto it is most definitely not required.
I have heard but haven't confirmed that premium fuel often has a better additives package (meaning extra stuff to help keep the motor happy), but even for a semi complex scooter like a water cooled fuel injected version (i.e. Honda Click, Honda PCX, Honda Air Blade), I've found regular seems to do just fine with no drops in fuel economy and no pinking, even under full throttle loads. It doesn't hurt to try though.
One thing I have found is that my old 2 stroke WOULD NOT START on regular for whatever reason, so if you have problems with an old 2 stroke running smoothly that may be your reason.
I'd personally watch for rural filling stations, not just because of "fast count" pumps (meaning they charge you more than what you've bought), but also because fuel might be suspect also. Plan ahead if you're going long distance and fillup when you can at a reputable station like Total, Caltex. I personally use only Total and Caltex, of course other stations might be fine too, I just have no experience with them.
Alright, stay safe and happy motoring
Reckless driving cucumber - 成
Thanks AE86. Great info, as always. Just a minor point, but there IS a relationship between the two octane rating systems. "Research octane" is the "r" value in r+m/2. It will usually be about 5 points higher than the USA/Canada system which takes the average of the two. I'm guessing the motos are OK because they were built in and designed for Southeast Asia in the first place.
You're right in saying that there is some relationship between the two, I was just trying make things clear that RON and R/M+2 (AKI) ratings are two different things.Buscador wrote:Thanks AE86. Great info, as always. Just a minor point, but there IS a relationship between the two octane rating systems. "Research octane" is the "r" value in r+m/2. It will usually be about 5 points higher than the USA/Canada system which takes the average of the two. I'm guessing the motos are OK because they were built in and designed for Southeast Asia in the first place.
As for motos, interestingly one of the main reasons they can take lower octane fuel without knocking is because their bore is so small so when the charge is ignited there is less chance for detonation to occur because of less distance to travel from ignition point to cylinder wall.
That's why a 12.5:1 compression ratio carbureted 50cc Honda doesn't require high octane fuel, but anything over 11:1 in a car usually does, especially if it isn't fuel injected. There may be some designs that take this into account, but given that a large number of scooters come directly over from Japan, receive no modification whatsoever to the motor and run just fine on "91" RON fuel over here, I suspect it's down the inherent characteristics of the small bore motors themselves.
Reckless driving cucumber - 成
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