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Old 01-14-06, 05:56 AM
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premium gas

Why do some car engines require pemium gas,are they better quality engines?
 
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Old 01-14-06, 06:07 AM
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The owners manual dictates which gas to buy, which is decided by the engineers that design the engine.

After that, Im not certain, but, I think higher octance means higher combustion force, thus higher power output when compared to regular octane engines.

Some would call that a 'better quality' engine, others would argue that it is merely a 'different' engine. Either way, a regular octane engine is NOT an inferior engine.

As a side note, I can't think of any car now-a-days that requires high octane gas, (except maybe cadilac?) but would love to hear from others that do know.
 
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Old 01-14-06, 06:20 AM
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simply put, higher octane fuel has a lower "explosion" point to perform better in high compression engines. regular grade fuels are subject to detonation at higher compression. so, actually, premium gives you less "bang" for your buck. if your engine ran fine on regular and now seems to preffer premium it could be an ignition timeing problem (ignition advanced) or carbon buildup on the combustion chamber causing an increase the the mechanical compression ratio. engines seem to take a liking to premium as they approach the 9.5:1 /10.0:1 range. since compression is an inexpensive path to performance some mfg's will spec premium fuel. today's electronc fuel injection, ecm's and knock sensors have helped. you could google "octane" for a more scientific explaination.
 
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Old 01-14-06, 06:57 AM
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Yes, octane gas has more resistance to exploding in the cylinder.
It is not any more powerful and in some cases it has less Mega Joules of energy available as compared to regular low octane gas.
It can feel more powerful because it allows the engine management system to advance the ignition timing more then regular gas without the gasoline "exploding" in the cylinder.
As far as a better or poorer engine, I would say that a quality engine will be better able to cope with or avoid preignition and detonation then the inferior engine. So I would say that an old worn out engine that has carbon deposits and sloppy engine components would need a high octane gas more then a good quality engine.
High performance engines are an exception. They get more power by more compression and timing (as flopshot has said) and need to protect themselves from the fuel exploding or igniting before it is time to do so.
You can imagine what would happen if the fuel ignited causing a flame front going down the cylinder while the piston is going up. That does happen and it is called preignition. High octane helps prevent this.
The fuel is actually designed to "expand", not "explode".
When it explodes it is called "detonation", as in dynamite.
You do not want dynamite in your cylinders either.
It is better to fix a problem with a vehicle if it is detonating or preigniteing then it is to cover it up with higher octane gas.
High octane has its problems also so don't use it unless you have to.
 
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Old 01-14-06, 07:03 AM
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just a little tidbit: top fuel engines are tuned to the point of detonation and will continue to run even when the mags have been blown out of the engine halfway down the track. in that world the guy with the most parts wins.
 
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Old 01-14-06, 08:19 AM
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Some vehicles can run worse on high test gas. Most Dodges that I have driven love regular unleaded, but when I put in the odd tank of high test to help clean the engine, they run horrendously.
 
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Old 01-14-06, 12:30 PM
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If you are supposed to use "Premium Unleaded Only", but use Regular instead, will is cause any type of damage to the engine and/or any other parts of the car?
 
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Old 01-14-06, 01:05 PM
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that "ping" you would hear is detonation. everytime you hear it you are losing material off the top of your piston and possibly the combustion chamber. it's caused by a section of the piston , combustion chamber, spark plug or a valve getting so hot it ignited the incoming fuel before the ignition system has a chance to at the proper time. it is also hammering the crankshaft at the connecting rod journal because the detonation takes place as the piston is coming up to top dead center. to paraphrase martha , it's not a good thing. if you have to use regular try a colder spark plug and retard the timing a few degrees. you will lose some performance. if it's an engine with an ecm have it checked out first. could be a sensor problem.
 
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Old 01-31-06, 03:57 PM
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Originally Posted by sjay
Why do some car engines require pemium gas,are they better quality engines?
Higher octane is simply a measurement of the gasoline's ability to resist pre-ignition or "detonation". It does NOT produce more power, clean your engine, or give you any more MPH or MPG that that silly decal on your rear window does.

If an automobile engine "requires" Premium gasoline, it is because that engine's fuel managment system controls the engine and produces the most horsepower and greatest fuel economy at the ignition timing settings that make use of premium fuel's resistance to 'knock'.

Higher compression engines (10:1 or better) generally require premium, to keep the fuel from exploding too early in the compression cycle, as explained above.

The type of fuel required is NOT any indication of the "quality" of the engine. It is merely an indication of the fuel management technology that was built in to the engine.

The Northstar in my Eldorado produces 300 horsepower out of 289 cubic inches. It reaches peak power at 6000 rpm. It gets me 21 miles per gallon. And it runs just fine on regular gasoline.
 
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Old 01-31-06, 04:33 PM
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premium gas

I drive a 1992 gmc suburban 4x4 5.7 Liters ( 350 c.i. ) TBI 210 HP, I use only premium gas on it and have no complains whatsoever , I'm always pulling a 2 axle dump trailer sometimes loaded up to 8K # GVW and the engine just performs flawlessly on premium and not as well on regular. MPG is really good for a truck that size, got the Flowmaster muffler and K&N Air Intake on it too and all I can say is I'm a believer.
Also my wife has a 2005 4x4 silverado crew cab 5.3 L ( 327 c.i.) 295 HP and same story we only use premium gas and man when you floor it you can feel where the extra money goes to,again not the same with regular.
Just my personal opinion.
 
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