Is there a REAL difference?

[bowtie_pasta]

I'm trying to gets some opinions and maybe some facts about whether premium (super) gasoline is better/any different than regular unleaded gas.

 

I've always ran the cheap stuff in my old truck and my new one gets the good stuff.  But I'm wondering if I'm just throwing my money away?  I could understand if I could really feel a noticable difference, but I can't.

 

Anyway, lets discuss.  

[Jpshostr]

The higher the octane the slower it burns.  Some people think its great, for general driving I think its a waste of money.  I get the best mileage out of the farm grade 87 octane out of our tank.

[bowtie_pasta]

Interesting, I would have thought the higher octane would burn faster.

[Jpshostr]

Interesting, I would have thought the higher octane would burn faster.

In theory, since the fuel burns so fast with a lower octane, not all the available energy is able to be used out of it since it happens so fast.  Slow down that burn some and you are stretching out the release of the energy.  With the speeds of the burn so very fast you can't tell from the driver's seat, unless you actually do feel additional performance.  I've filled up with 91 and 93 a few times in my Grand Prix, sure wasn't able to tell anything, actually like the grade I said above better.  Why should I pay $.20 more a gallon for stuff that is senseless to put in?  Now I know for some vehicles out there you need to put in higher octanes, but most don't require it.  

 

Now watch all the street racers here come and blast me, as always happens.

[TxDoc]

Some good Octane info:

 

http://f.about.com/z/js/spr00.htm

 

http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

 

 

http://www.cyber-north.com/autotipnet/octane.html

 

Basically, no need for it in a stock engine. Higher octane rating does not mean more latent chemical engergy. The higher octane rated fuels have additives to stop he pinging or knocking associated with pre-detonatiion.

The octane number is a measure of a fuel’s resistance to pinging/knocking. This pinging or knocking occurs when a fuel does not burn consistently across a combustion chamber. Instead, while the flame is spreading across the chamber, others areas of the fuel beginnng burning spontaneously, causing a violent collision of the flame front. Which is what causes the pinging. Raising the octane number of the fuel makes the fuel burn consistently across the combustion chamber. Severe damage can occur if an engine pings or knocks for long periods of time. Up until the mid-seventies, tetra-ethyl lead was added to the gas at the refinery to raise the octane of pump gas and to provide a protective barrier for valve seats. It was phased out after it was found a health hazard. Today’s valve seats are hardened and do not require this protection. The old valve seats are soft and will micro-weld. And the slow recession of the valve seat under high temperature conditions.

[sincityZ71]

Yeah, there really isn't to big of a difference between the grades, especially for the engines we have.  I happen to use mid-grade all the time, because I feel the truck runs a bit smoother then it does on regular.  My mileage is usually a little better with the mid grade too, but only during summer months when it is 91 oct.  In the winter here they mess with the gas and drop down the octanes, so 91 becomes 89, and I always get my worse milage in the winter months.  Which is sad considering I have to run a/c in the summer, and I am getting better milage in the summer then the winter.  Go figure...

[bowtie_pasta]

Well, thanks for saving me bucks guys!!     I know the truth now and will probably try the better gas in the old rig and see if it helps the pinging/knocking.

[Dihappy]

Great post Doc!!

 

There is a lot of misinformation out there about fuel.

You should stick with regular octane or plus gas. If your vehicle does not exhibit any pinging or knocking when using the regular octane gas then stick with it.

 

Higher octane fuels are only designed to help high compression engines like sports cars or older high horsepower cars.

 

My GTO has 10.75:1 compression and i have to use super unleaded, and then some.

 

Im not certain, but i would guess that most new trucks have a compression ratio of approx. 9:1 and should be ok with plus.

 

Personally, i have found my truck runs quite well with plus gasoline, that is until recently when i programmed it for 93

 

Dont fuel up blindly, if it works, then stick with it.

 

Some non platinum plugs would also help.

 

 

Id also recommend:

http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

[hogger999]

I was gonna say you should be burning the 93 in the old truck and 89  or 91 in the new one but you,ve already come to that conclusion.

 

In 94 I bought a brand new S-10 SS, I was 18 and it was my first new vehicle and I wanted to take care of it. I burned nothing but Amaco ultimate 93. After 5000 miles the fuel pump went bad and the service tech. told me it was because of the high octane fuel. I still have a hard time swallowing that one.

[GnatGoSplat]

The Premium Myth on Quiktrip.com

 

My truck pings under load sometimes on 87-octane, but I run it anyway because I'm cheap.

[MarkD]

Great Post Doc!  

 

I have always used volatility to explain the difference (same thing).

[Guest]

Another thing to consider about which octane to run besides your compression ratio, (which none of us have to worry about with our trucks) is altitude... the lower the altitude the faster the fuel burn... Thats why in Houston they sell 96 octane to run in your porsche vs. a highest of 91/92 octane they sell around here in Southwest NM and El Paso (right around 4,000ft alt) 86/87 octane is fine for our trucks... I see no reason anyone should think they need to run a higher octane than what our trucks are enitially designed for... Another thing i hate is how people go and buy octane boosters.... this doesnt help anything... It doesnt make your car faster   Ive seen it first hand that it doesnt... But I cant help but think how nice it would be to own a company like "104+ Octane boost..." Easy money to make off of tons of uneducated, gullible people...  

[TxDoc]

I've seen two posts referring to "fast" burning of fuel.  I have never seen where rate of burn had anything to do with transference of chemical to mechanical engergy--assuming a complete burn of fuel occurs.  Are you making reference to gas expansion over a larger excursion of the power

stroke?

 

With a computer-controlled, EFI engine, altitude should not be a problem with automatically correcting for variance of ambient air pressure differences(oxygen content per unit volume of air). With an engine like an ATV with a fixed jetting, it could be a major source of power loss to go from sea level to high in the Colorado mountains.

 

Any info or clarification is welcomed.

[WEFs99]

I'm convinced that the additives in "Super" grades do help in keeping plugs and injectors clean so I feed my truck and old van a tankful a time or two per year. The rest of the time it's cheapo grade.

[SilveradoWV]

I have always thought that the truck gets used to a certain octane! Like if you run 93 all of the time then go to 87 it runs worse or something like that! (Old Wives Tale I made up) LOL!I always run 87!