ViribusUnits,

Email this guy... zmts@aol.com

He sells plenty of manuals on EBAY and may have one for your year.

I've bought several paper products from him and have been happy with them.

Tim
<img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

Okay. I did a little homework; I found these webpages very informative (see further below). Here is what I've read.

RON = Research Octane Number

MON = Motor Octane Number

CLC/AKI (also known/called Road Octane Number)
= Anti Knock Index

RON + MON/2 = AKI or CLC

Major gas companies in Canada and USA all post the AKI/CLC figure (RON+MON/2) at the pump.

If your car is old, your manual may only tell you the RON. "A rule of thumb is that RON of a gasoline equals to AKI + 5". So a RON 95 is a AKI/CLC = 90. My 1988 manual calls for 95 RON or 90CLC/AKI. Therefore, the "right" ocatane level to purchase as posted at the pump is 90 (although I only every see 91 or 92 so that is the next closest but higher level).

Two other interesting points of note is: (a) as a car gets older it may need a higher level of octane ... to keep the knocks away.., and (b) another feature of gasoline is the type of 'deposit control additive' used. At Chevron, (I use only as an example as I note a very common product used), the higher the octane level the higher the amount of deposit control additives in the product (this I'm being told is a good thing). So one other reason to use the higher octane level is a cleaner engine. But buying higher octane say 94 (which is available) is a waste of money... unless your car is old and you're still getting knocked up.. so to speak!

The webpages are:

<a href="http://www.chevron.ca/ProductsServices/Retail/Gasolines.htm" target="_blank">http://www.chevron.ca/ProductsServices/Retail/Gasolines.htm</a>

<a href="http://www.chevron.ca/FAQs/FAQsGasolines.htm" target="_blank">http://www.chevron.ca/FAQs/FAQsGasolines.htm</a>

<a href="http://www.shell.ca/code/motoring/encyclopedia/gasolines/octane.html" target="_blank">http://www.shell.ca/code/motoring/encyclopedia/gasolines/octane.html</a>

<a href="http://www.shell.ca/code/motoring/encyclopedia/gasolines/quality_gasoline.html" target="_blank">http://www.shell.ca/code/motoring/encyclopedia/gasolines/quality_gasoline.html</a>


Hope this helps, it did me.

p.s. And yes to my earlier ps question, city vs. highway does make a difference too. A higher octane may be needed if you a) make a lot of short trips, b) drive in high temperatures, c) drive in low altitude areas (which I think is why Chevron sells 92 in Vancouver but 91 elsewhere in British Columbia).

p.p.s. higher octanes does not equate to more hp.

Bruce. <img src="graemlins/wave.gif" border="0" alt="[byebye]" />

 

Why higher as the car gets older?

That doesn't make sence to me.

The compression isn't going up on the car. The ingnition isn't changeing. So why have higher octane?

Thanks

 

VU: As I understand it, the older the car gets, deposits accumulate more and more in the engine's combustion chambers; these 'bad' deposits can cause knocking and lead to poorer performance. The higher octanes have a higher level of deposit control additives (improves the engine combustion). Or to put it another way "a clean engine is a happy engine", at least that's what my research reading seems to say, which makes sense to me.

B. <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />

 

I checked my 928 S Owner's Manual - Model '83. It says on page 97:


Fuel recommendation

91 RON (87 CLC on U.S. fuel pumps) minimum. UNLEADED FUEL ONLY.

 

Viribus -
As deposits accumulate in the combustion chamber the volume of the combustion chamber gets smaller. Since the stroke of the piston stays constant over time the compression ratio will rise. More deposits = smaller combustion chamber volume = increased compression ratio. Also, over time valves and piston rings tend to seat better (ie. less blow by) which can also increase compression ratio. Until you reach the point where blow by increases (lots of mechanical wear on cylinders, valves and valve seats or excessive deposits) the compression ratio can increase.

 

Should you get enough deposits to make that big a diffrence?

Seems to me that would be an awful lought of depoits...

 

Well, it's good to know that the octane booster is a rip off.

What is your opinion of the Fuel Injector Cleaner stuff?

Does it work?

Thanks

 

VU: If you believe Chevron's info, using their fuel with 'Techtron' regularly and then using their Techtron Concentrate every 5,000 will clean your fuel injectors nicely... hey, and I don't work for Chevron. See this webpage for more info:

<a href="http://www.chevron.ca/FAQs/FAQsFuelAdditives.htm" target="_blank">http://www.chevron.ca/FAQs/FAQsFuelAdditives.htm</a>

<img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

OK, just to throw a little fuel on the fire...

There is one thing in this discussion that can alter any personal experiences we have: the gas you are paying for may not be the gas you are getting.

1) Having some close ties to the gas biz, I know that most gas for retail sales comes from the same depot. The majors add their additives at the depot - most of the time.

2) If you buy your gas from a company owned location, you will most likely get the gas as advertised. If you buy your gas from a dealer, that dealer may not always get the brand name stuff.

3) Contaminated gas is a much bigger problem than most people think. Like dealer fraud, the evidence is consumed so quickly that complaints are very hard to prove

4) Gasoline is a commodity. The oil companies do not necessarily control the product from the ground to the pump. Excluding the depot addititives, for a given grade, gas is gas.

So, don't judge any performance change by one tank of gas - try it for a few tankfulls.

 

The following is from the December issue of the Excellence magazine, Page 160, in which author Jim Pasha answer to reader's questions.

Question: Will my Boxster perform better with higher octane gasoline?

Answer: I recently did some informal performance measurements with the meager 91 octane gasoline we get in California versus the 96 octane gas sold at the racetrack and available on the east coast. My informal test results were startling. The 96 octane fuel dropped th 0-60 time by almost a second. Furthermore, while I had attributed an off-the-line hesitation to my car's Tiptronic transmission the better gas cured the problem - so I now think the low-quality fuel is causing the DME to go into a performance mode that is safe for the engine but frustrating for the driver.

Porsche's stated output figures are generated with a spec fuel not available in California or certain selected states. To offset this problem, some manufacturers gear their cars for better acceleration to make owners think they are getting more power. In short, developing the advertised power in real-life situations with fuels as poor as we are seeing produced today might be tough. Certainly, this is a subject worth further investigation.

Also, in Novemeber 2001 Car & Driver tested regular versus Premium gasolines in several vehicles, all but one vehicle produced higher horsepowers and faster accelerations, albeit, very slightly.

Happy pondering )