Question for experts on fuel.

[colosilverado]

Does/can running the high octane stuff that is rated over 100 hurt the Vortechs at all. We have a station close by now that sells the high octane stuff and I thought about trying it. I don't know why, because I know it won't do anything for me. I guess I just wanted to say I tried it. I don't wanna hurt it though. It is bone stock and 5.3L..........

[TxDoc]

Here's my "octane info"--I am not an expert, though.  It's mainly a waste of money with no result.

 

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

 

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.

 

 

Octane Links

 

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

[colosilverado]

Cool, thanks for the info TxDoc! Nice truck BTW, doc! I have been debating in my mid whether to get a new Sierra but I love my '99 so much, I can't come up with enough reasons to replace it! How do you like the white as far as keeping it looking nice? It looks sharp, I think! I just take mine offroad quite a bit and the pewter is easier to hide the dirt on.

[TxDoc]

This is my second Summit White. My other was a 97. It just does not show scratches like black or red will over time.  It is cooler in the summer and visibility is higher so you may be seen better and have less chances of getting into an accident--although an unlicensed, uninsured driver hit me from behind with no damage as I had my trailer hitch installed. When dirty, it doesn't really look bad, unless you clean an area and stand back and look again.  I like it. My g/f said she read that people who drive white vehicles are "aloof".  Okay.  

 

Check and see what others think on the octane question, too.

[bcfitzsimons]

Be careful and look on the pump before you put that gas into your tank.  I don't know if I believe "the hype" about higher octane gas causing heavier intake valve deposits, BUT even if that's not true, usually the only way any refinery is able to get octane numbers over 99 or 100 is by adding lead.  The reasearch octane number that you see on the pump, if I remember correctly, is determined by the percent hextane ("bad" gas) plus the percent 2,2,4-trimethylpentane ("octane," or "good" gas).  What you see advertised on the pump is usually the average of two different ways of calculating the octane number.  Back in the "old days," when lead was used, the octane number was the average described above PLUS the number in milliliters of tetraethyl lead added per gallon of gas (i.e. one gallon of 87 octane plus 15 mL of TEPb gave you one gallon of 102 octane).  

 

Now, you might say, "but I thought leaded gas can't be sold in the US . . ." and you'd be right if you were talking about for use in street cars.  However, leaded gas is still used for racing, and it's still available at a few service stations.  There's one around here in south Cleveland that sells it-the only caveat is that you can't put it into the car that you drive up to the pump-that is, you can only put it into a car on a trailer, or into a can.

 

So, like I said before, I'd check before you put that stuff into your tank.  Otherwise, you'll be spending a lot more later on-

 

HTH-Fitz

[CapnDean]

I became an expert on Preignition (aka valve rattle, engine ping, & spark knock) while I was suing Chrysler to repurchase my 99 Ram that pinged.

 

#1) Don't use Premium if you don't need it.

#2) If you do need it find out why.

 

Ping = Your mixture in the cylinder exploding BEFORE the spark plug fires.  Bad Ju ju, not good for engine longevity OR performance.

 

This is what a diesel engine does- - compresses the mixture til it blows rather than relying on a spark to set it off.

 

Premium gas (believe it or not) is LESS likely to blow when compressed than is elcheapo unlead ergo premium can help a pinger not ping.

 

Retarding the timing is the basic solution to ping although it cost you in performance and economy.

 

The optimum performance of any engine is reached at the very threshold of ping.  In a perfect world of course.