I've never put anything but regualr. It says in the manual what grade is required.

 

Hyundai's are designed for regular (approx 87 octane) fuel , at least here in the USA. If too high of octane fuel is used, it will create excessive sludge and carbon build-up at intake valves, injector pintle areas and combustion chambers due to incomplete combustion/burn. Most people think higher octane fuel causes air/fuel mixture to burn better, faster or more robustly. This is the exact opposite. High octane fuels burn more slowly and are more suited for high compression engines that will otherwise detonate if low octane fuel is used.
In fact, I recall a TSB that Ford issued for Ford owners in the northern states. It stated that using high octane fuel may cause excessive cranking times or even a no-start condition in colder weather due to the higher octane's inherent lack of volatility .
At the Hyundai traning center, the Field Engineer compared the intake valve of a Hyundai engine using correct octane with a Hyundai engine that used an octane that was too high, and the soot/carbon build-up was excessive to the point of causing fuel absorbtion and subsequent misfire...

 

NOT SO!!!!!

The owner’s manual states: “87 octane OR HIGHER is recommended”
Hyundai engines are high compression engines (10:1 and higher depending on the model), and one should fill the octane suitable for the ambient temperature.
Winter time (freezing) = 87 octane (AKI) would be OK;
Summer time (20°C (70°F) and higher) = 89 octane (AKI) would be better;
30°C (83°F) and higher = 91 octane (AKI) would be better.
The higher the ambient temperature = the higher the combustion temperature = the more active is the knock sensor = the more is the ignition retarded.
Retarded ignition time = loss of engine power.
Yes, all Hyundai’s can run on 87, and the knock sensor will protect the engine from damage, but the engine performance will suffer.
Poor engine performance = poor fuel economy.
Yes higher octane cost more, but if you calculate $$ per km or mile, you will see that it cost you the same or most likely less that lower octane. It all depends on the season (ambient temperature).

 

Originally posted by duke@Apr 14 2007, 06:26 PM
NOT SO!!!!!

The owner’s manual states: “87 octane OR HIGHER is recommended”

You are totally wrong. “87 octane OR HIGHER is recommended” means not to use less than 87. Using 89 or higher is just wasting money on a stock engine. Unless you have Forced Induction, you gain ZERO performance from using higher than 87 octane.

 

Originally posted by NovaResource@Apr 14 2007, 06:56 PM
Unless you have Forced Induction, you gain ZERO performance from using higher than 87 octane.

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And I bet you believe that OCI every 100,000 miles are OK!

 

At the price per gallon I don't think anybody will be able to afford more then regular. In New York way over 3 dollars a gallon for regular.

 

Hyundai101 : how long you've been using regular? and do you notice any problems?

robtemple: well the common preception is that even if you use higher octane than recomended; it will not harm the engine ..... but from your reply it seems that it does......

the compression ratio is 10:1 which is moderate i think so the option of high or low octane is up to the user, but still we dont know as for long term usage which one is better ..........................

 

The compression ratios of the engines are:
Accent 1.5 & 1.6, Elantra 2.0, Tiburon 2.0 & 2.7, Tucson 2.0 & 2.7, SM Santa Fe 2.4 & 2.7 = 10:1
NF Sonata 2.4 & 3.3, Azera 3.8, CM Santa Fe 2.7 & 3.3, EN Veracruz = 10.4:1

I have tested this theory many times on all these models, and came to the same conclusion. Furthermore, a multi-valve engine (which all Hyundai’s are) should be driven/cruising at the 2000 ~ 2500 rpm range to be more acceleration responsive and economical. This means, that cars with Shiftronic should be using it in city driving up to mostly 3rd gear. Cars without Shiftronic, select “3” (or OD-OFF) and not “D” in the city.

IT ALL DEPEND ON THE AMBIENT TEMPERATURE

Why not try it, and calculate the $$$ pet km or per mile

 

I have always gone with the recommended fuel, always used regular and never had a problem with it. Just a foot note, used to work at Gas station out here in montreal Canada, I found out that upon taking the readings for the fuel levels, The middle grade of gas did not exist, turns out that the manager who i had become good friends with told me that when people bought the middle grade gas, they actually got the regular. Don;t know if all stations are like that, but this one was. After that revelation, its regular all the way for me

 

Of course, there are only 2 tanks in the gas stations, 87 & 91 octane, but the pump will blend the gas 50/50 to create 89 at the nozzle. :amen:

 

robtemple,


You quote:
Hyundai's are designed for regular (approx 87 octane) fuel, at least here in the USA. If too high of octane fuel is used, it will create excessive sludge and carbon build-up at intake valves, injector pintle areas….

CORRECTION:
Sludge and carbon build-up at intake valves will only happen on engines with an EGR valve. Only the Mitsu-based 1.5, 2.4 & 3.5-liter engines have one, and the exhaust fumes create the “sludge” been recirculated.

You quote:
and combustion chambers due to incomplete combustion/burn.

CORRECTION:
Incomplete combustion/burn is the result of too rich a mixture due to stop-start driving, too cold engine (wrong or faulty thermostat), poor ignition, or retarded ignition due to too low octane.

You quote:
Most people think higher-octane fuel causes air/fuel mixture to burn better, faster or more robustly. This is the exact opposite. High octane fuels burn more slowly and are more suited for high compression engines that will otherwise detonate if low octane fuel is used.

CORRECTION:
High octane burns at the same rate as low octane, but the flash point (self ignition point) is higher. Therefore it can take a higher compression temperature before is self ignites, which is the case of advanced ignition timing and high AMBIENT TEMPERATURE.

You quote:
In fact, I recall a TSB that Ford issued for Ford owners in the northern states. It stated that using high octane fuel may cause excessive cranking times or even a no-start condition in colder weather due to the higher octane's inherent lack of volatility.

CORRECTION:
Do I not keep on mentioning about the importance of AMBIENT TEMPERATURE?
Besides, I do not know at what compression ratio most Ford engines have.

You quote:
At the Hyundai training center, the Field Engineer compared the intake valve of a Hyundai engine using correct octane with a Hyundai engine that used an octane that was too high, and the soot/carbon build-up was excessive to the point of causing fuel absorbtion and subsequent misfire...

CORRECTION:
The “Field Engineer” most likely showed you a valve of an engine with EGR valve, which today’s engines do not have anymore.
As I stated over and over, it all depend on the AMBIENT TEMPERATURE.

:amen: to that!
it is amazing what you can learn in 45+ years in the motor trade!!!!

 

Originally posted by duke@Apr 15 2007, 08:45 AM
IT ALL DEPEND ON THE AMBIENT TEMPERATURE

You are incorrect again. Unless you have a modified engine that requires higher octane (forced induction, higher compression pistons, more aggressive cam, increased timing from an aftermarket computer) you gain ZERO performance from using higher than recommended octane fuel. If your car calls for 87, you will gain nothing from using higher octane.

If your car pings on 87 then there is another problem with your car. Get that fixed. Using higher octane fuel only masks the actual problem. Using higher octane fuel than required is only wasting money. Ambient temp has nothing to do with a stock, unmodified car. If the car is designed for 87 octane, it's designed for that fuel UNDER ALL DRIVING CONDITIONS AND TEMPS.

I have done many tests on fuel octane with my Tib. I can tell you from experience, I gained ZERO performance increase from higher octane and ZERO mileage increase from higher octane.

If you feel better buying higher octane, feel free. It's your money, not mine.

 

If you don't mind me jumping in here. Many of the engines today have knock sensors, which will r-e-t-a-r-d timing if it detects pinging. It will prevent your car from pinging, but what happens when the timing is retarded? You will lose power and fuel economy. I would say that both theories are right, depending on the circumstances. If you are getting low fuel economy, switching to higher octane fuel MAY help if the problem is action from the knock sensor. Otherwise, I agree that higher octane won't gain you anything.

As for me, I only use 87 octane...

 

guys

we all know that you can operate cars on either fuel, and even i feel that regular is better in performance than super (may be the circumstances were different since i was in dead sea which is the lowest spot on earth ).
but does it really damage the engine or not ?

as for the mileage my santa fe is already a very bad mileage rate so i am trying to balance things by using regular since the price is 30% less than super or high octane.

 

fmfm,

Where is "JO"... Jordan ???
Also, what is the octane rating on the pump, is it MON, RON or AKI ???
What are the octane choises available ??

 

Originally posted by duke@Apr 16 2007, 04:48 PM
fmfm,

Where is "JO"... Jordan ???
Also, what is the octane rating on the pump, is it MON, RON or AKI ???
What are the octane choises available ??

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yes Jordan

octane rating ???? :grin: :grin:

we have regular or super or unleaded, i think regular for 87 and super 91

no chioces here :whistling:

 

Ok, here I go again, I try to keep it low-tech.

Combustion process:
The air-fuel mixture burning duration (at mixture of 14.7 parts of air to 1part of fuel) is +- 3.5ms (depending on combustion chamber design). The mixture is ignited +- 1/3rd of the time at BTC (Before the piston is at Top dead Centre), and continues as the piston descends after TDC (Top Dead Centre).
As the plug ignites a tiny flame, and the flame expands (like a stone into the pond creates ripples), it creates heat, and want to expand. BUT, the piston is still going up towards TDC, and compressing the wanting to expand mixture further. This in turn will heat the mixture further, which will speed the burning and heating process.

Pre-ignition:
If the mixture is ignited too soon, the mixture will get hot enough to overheat a particle (piece of carbon or machining edge etc.) in the combustion chamber (or piston top). This hot spot will act as a plug, and at the next compression stroke, will ignite the mixture just before the plug does. Now you have 2 flame fronts, and as they collide, you hear the PINKING. This pre/self ignition creates a sound frequency of +-5550zh, which the knock sensor is tuned in to. Should this occur, the sensor signals the ECM, and it will **** the plug ignition of that cylinder. This will prevent a flame collision, and hence, no pinking.

Ignition process:
All today Hyundai’s have a high compression engine of 10:1 ratio or even higher, meaning, that the piston compresses its sweep-volume into a 1/10th big a volume (combustion chamber).
At high ambient temperature, and with 87octane fuel, the ignition time will be somewhat retarded under certain engine loads. At 91octane fuel, the timing is more advanced towards where it should be. The advanced timing creates a higher combustion temperature, and with it more power on the down stroke of the piston.
The higher octane is more resistant to pre/self ignition, and therefore will not self ignite on the next compression stroke.
There are other factors to consider. In the wintertime, where the ambient temp is in the freezing range, the cold intake air (no pre-heated air with fuel injected engines) alone causes lower combustion temp and is more “unfriendly” to ignition. A lower octane fuel will help compensate for it.
In summer, there is a different scenario. The warm intake air will add to the pre/self ignition possibility, and the result with low octane fuel is, a more than necessary retarded ignition time.
Thanks to the electronic technology, doe to the presence of the KNOCK-SENSOR, one can get away with 87 in the summer. This on the other hand will not give you the capable performance or the fuel economy.
With the help of the knock sensor, the ECM will advance the ignition time to the maximum possible, and always close to the pre/self ignition threshold.

The owner’s manual states “MINIMUM of 87 octane fuel is recommended”. Hyundai finally realises this mistake, and as from 2002 states “MINIMUM of 87 octane fuel OR HIGHER is recommended”.

If higher octane would be harmfull for the engine, then Hyundai would not recommend it.........or would they??????????????

I hope I was clear enough.

 

Like I said before. If your engine is knocking or pinging there is another problem with your engine. Your engine, if in proper working order, will not ping on regular (in the US that is RON+MON/2 = 87). If your cars pings on regular THERE IS SOMETHING WRONG. Using higher octane fuel only masks the problem. It treats the sysmtom, not that cause.

Will you loose power if your car pings? Yes because the computer will **** the timing to prevent the ping. However, higher octane fuel only returns the previous performance, it doesn't ADD any. If you fix what is causing the pinging you will also gain the power back with regular fuel. There is a difference between adding ignition timing advance (that will create power) and "not retarding" the ignition timing.

 

I have always thought that putting a higher octane gas like premium or super will burn better than low octane gas like regular so that the engine does not have to work harder, which reduces carbon build up.

I have a 04 tundra 3.4L v6. It says to use 87 or higher. I always use 91 and whenever I use 87, the car doesn't seem to go as it does with 91. It seems to run better with 91 than with 87.

I'm getting really confused now with other posts.

maybe it really doesn't matter to use 87 or 91 if the minimum required fuel rating is 87 ?

With the other vehicle 98 isuzu rodeo 3.2L v6 that I used to have.
Whenever I used 87, it seemed to have some pinging sound when I accelerated, but with 91 the pinging sound was reduced.

 

Originally posted by sonatalove@Apr 16 2007, 10:28 AM
I have always thought that putting a higher octane gas like premium or super will burn better than low octane gas like regular so that the engine does not have to work harder, which reduces carbon build up.

That is not true. Higher octane fuel is just more resistant to detonation.

I have a 04 tundra 3.4L v6.  It says to use 87 or higher.  I always use 91 and whenever I use 87, the car doesn't seem to go as it does with 91.  It seems to run better with 91 than with 87.

I'm getting really confused now with other posts.

maybe it really doesn't matter to use 87 or 91 if the minimum required fuel rating is 87 ?

With the other vehicle 98 isuzu rodeo  3.2L v6  that I used to have.
Whenever I used 87, it seemed to have some pinging sound when I accelerated, but with 91 the pinging sound was reduced.

If it was designed to 87 and it pinged then there was a problem with the engine. Carbon buildup on the pistons, timing problems, ignition problems, etc... A higher octane fuel made the pinging go away because it resists detonation better but that didn't solve the actual problem that was causing the pinging in the first place.

The resaon the manufacturer says "87 or Higher" is because 87 is the minimum rated octane fuel you should use. It means that higher won't hurt but it does not mean that higher will help.

 

Originally posted by sonatalove@Apr 16 2007, 10:28 AM
I have a 04 tundra 3.4L v6.  It says to use 87 or higher.  I always use 91 and whenever I use 87, the car doesn't seem to go as it does with 91.  It seems to run better with 91 than with 87.
maybe it really doesn't matter to use 87 or 91 if the minimum required fuel rating is 87 ?

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Sonatalove.
91octane maybe overkill, what I'd do is try 89octane and see how it goes.
The octane rating at the gas station is an average so when you are pumping 87octane you may not be getting 87 at that particular time or pump, that's why I use 89, just to be sure. Your computer will adjust the timing if it fall below 87, but I'd rather keep it in the proper range.

 

How come some of you say put super and some say regualr? Its making it so confusing to decide.

 

Originally posted by NovaResource@Apr 16 2007, 04:35 PM
That is not true.  Higher octane fuel is just more resistant to detonation.
If it was designed to 87 and it pinged then there was a problem with the engine.  Carbon buildup on the pistons, timing problems, ignition problems, etc...  A higher octane fuel made the pinging go away because it resists detonation better but that didn't solve the actual problem that was causing the pinging in the first place.

The resaon the manufacturer says "87 or Higher" is because 87 is the minimum rated octane fuel you should use.  It means that higher won't hurt but it does not mean that higher will help.

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the pinging sound occurs for my car when I accelerate harder.
maybe it's not really the pinging sound but it's some sort of valve clicking sound during the hard acceleration. It doesn't occur all the time, it used to occur once in a month. After switching to higher octane, I don't hear valve clicking anymore during hard acceleration.

I'm curious about why sports cars do require higher octane, isn't it because they get more power from using higher octane?

I once switched back to 89 and I was just not getting the acceleration that I used to get with 91.

Will it hurt my engine if I use 91?

It just seems that my engine does not have any problems with 91.

 

Summary

thnx to every one who posted here, what i understand that:

High or low octane will differ in knocking, with the new cars this was eliminated with advanced monitoring and controlling system, low octane could cause slight performance loss, yet nothing more serious could happen to your car.

so peace of advice, if you are a city driver go for regular coz in rush hour all gas will be the same.

 

Originally posted by NovaResource@Apr 16 2007, 06:21 AM
Like I said before.  If your engine is knocking or pinging there is another problem with your engine.  Your engine, if in proper working order, will not ping on regular (in the US that is RON+MON/2 = 87).  If your cars pings on regular THERE IS SOMETHING WRONG.  Using higher octane fuel only masks the problem.  It treats the sysmtom, not that cause.

Will you loose power if your car pings?  Yes because the computer will **** the timing to prevent the ping.  However, higher octane fuel only returns the previous performance, it doesn't ADD any.  If you fix what is causing the pinging you will also gain the power back with regular fuel.  There is a difference between adding ignition timing advance (that will create power) and "not retarding" the ignition timing.

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You wrote:
(in the US that is RON+MON/2 = 87)

CORRECTION:
RON+MON/2 = AKI

The ECM is not adding ignition timing; rather it is now able to achieve proper ignition points without retardation.

Please do first some research, before you contradict.
Ambient temperature is a great factor to engine performance (not only for race cars), especially when the engine has a 10.4:1 compression ratio.