You're absolutely correct. It is your money Greenshirt. Invest it where you think it's important. Some of us are more frugal than others. If you think you're getting good value out of 92 octane then by all means spend as you see fit.

I belong to several auto Forums and this subject has always been arguementitive and with strong convictions. I've learned after a couple of attempts it's best to let it go and move on. Cheers.[sm=icon_cheers.gif]

 

of course every car is different, and I made sure to spell out all the differences and note that it's my personal experience. Likewise, neither the twin turbo, nor the ECM have anything to do with the very noticeable acceleration increase. As some have correctly observed, it takes at least after one or two full tanks or premium to notice the difference with regular, since ECM needs time. In my case, I noticed an immediate improvement. So once again, neither the turbo nor the ECM could have had anything to do with this, and I was simply too skeptical at the time myself.

All those studies are great, but as many of you noted, it all depends on a variety of conditions, ranging from the type of car and engine, to weather and elevation factor. I don't know what is best in case of the new H3 Alpha, but the dealer told be 87 octane, same as the manual. Meanwhile, some of the users here do claim that it's still better to put in premium or mid--grade.

Which brings a point -- why does mid-grade (89) even exists, if all cars require either 87 or 91/93? At least I've never drove or owned cars that required 89 -- and I drove and owned many cars.

 

Mid grade is there to convince the person psychologically that "at least it's not the last one". Satisfies a persons guilt and doesn't kill the wallet. I've seen gas stations with 5 diff octane types... go figure.

 

The old 97-2003 Pontiac Grand Prix GTPs, the Buick Riviera, and the last generation of Impalas w/ the Eaton Superchargers..........all called for 89 or higher.

 

[/quote]
I belong to several auto Forums and this subject has always been arguementitive and with strong convictions. I've learned after a couple of attempts it's best to let it go and move on. Cheers.[sm=icon_cheers.gif]
[/quote]

I hope I didn't come across as arguementitive. That wasn't my intention at all.
Just wanted to put in my .02 per gallon. ha ha
I know- horrible pun.

 

I have to fill up my tank pretty soon onmy dime. Factory fill is about out. I'm going with 93 Shell V-Power. I have always used this fuel.

 

Audil, your observations with your Audi are spot on. Vehicles with hgh compresion ratios or forced induction require, and will perorm better with higher octain.

I'm not sure how the PCM is "learning" what octain fule you are running after running a tank. The PCMwill retard the timing from thedefaultif the knock sensor detects knock. This dosn't take a tank full of fuel, but a split second. It dosn't have any way of knowing that advancing the timing would be benifitual.

Why does midgrade exist? For some vehicles, like Doc Olds pointed out,its what is required. It is also an option for engines designed for low octain that have developed issues with pinging to increase octain without going all the way up to premium.

That's enough "debateing" for one morning... I've got a CB to install.

 

CB??Like a Citizen Band Radio...Good Buddy? Are they still using those?
I had one in the '60s. My handle was RamRod. I loved ridin' in the "rocking chair"

 

PCMs learn like this: Attention PCM students, class is in session, we have learning to do today!

Suffice it to say, when digesting octane, timing is based upon spark curves, not straight lines, that require blending with other factors. Those little buggers can detect what is happening, store it in their 32bit flash, and burst flash, memory and create a data table to draw conclusions as to how to modify the spark curve base on YOUR PRIOR DRIVING to most efficiently operate the engine systems. These things store like billions ofnumbers!! Yikes! "Block learing" is oneof the easiest examples. [sm=sleeping.gif]
I am not talking about direct sensor operating,for instance,the PCM getting a knock code directly from the knock sensor. That response comes from a programmed fixed data table.

It is amazing really, from this old guy's perspective where tuning a car used to be ALL mechanical?

Reading? http://www.gmhightechperformance.com...ms/page_4.html; freaky voice guy: http://para.noid.org/~lj/PCM%20Tutorial/PCMtutorial.htm, makes me noid??? Note: this is an out of date overview, our PCMs are way more advanced than pre 2005, like 4 times more data capacity and 10 times faster.

 

Doc,
I bet you're old enough to remember weights and springs in your distributor!! and even floats in your fuel system?

Maybe we should call you "Old Doc"?[sm=lildevil.gif]