I know this is old stuff, but I would like some input (hopefully informed)
on current thinking, now that gas prices have skyrocketed and there is a
real financial significance that just didn't exist "in the olden days".
Here in British Columbia, Canada we are paying $1.17/litre in $Cdn or 1.17 x
3.785 (l. / U.S. gal) x .86/1=$3.80 U.S. / U.S. gallon.....and that's for
regular. Let's look at about $4.10+ U.S. / U.S. gallon.
The book for my car 2001 V70xc recommends a minimum octane (RON) of 91, and
I see regulars at 87 and mid-range at 89. I listen to Radio Station KGO (San
Francisco) at night and often hear their science Guru Bill Wattenberg (PhD
etc. etc. knows all, et al) who says, "If it will run on regular, use
regular. A modern sophisticated car engine may not run initially that well,
but sensors will "re-tune" to the lower octane and will be fine.....no
damage.....no power loss.....no effect on warranty. The theory, as I
understand it is that "higher octane" doesn't mean more "power" in the gas,
it means elements added to adjust combustion rate. In his opinion higher
octanes are "generally speaking" a scam on automobile users perpetrated by
the oil companies and encouraged by the auto manufacturers.

What's the consensus?

Gerry

"gerry" <notforgenerause (AT) nospam (DOT) com> wrote

Ah....
the Truth.
There is no truth, there is just perceiption.
There also is no consensus on this I am afraid.
And since when is truth determined by consensus?


Anyway...
MY EXPERIENCE is that the higher octane fuels will cause the engine to run
more efficiently, somewhere around the same percentage as the price is
higher.
So... if the higher octane stuff is around 10% more expensive, then I get a
milage that is around 10% better.
This has been "More Or Less Accurate" (= True? ) since the first time I
did the calculations for my Saab 99. Since this car did not have any
"intelligence" built in (you had to get in the car first yourself) it didnt
adjust to the fuel by itself.
So.... I got fed up with tuning to a different fuel and did the
calculations.
In the end I stuck with the higher octane fuel.

If I was/had an oil company, I would make sure my fuel was priced so that i
would sell the most, OR make my profits as high as possible.
If my high octane fuel did not have enough benefits, then I would have to
lower the price OR improve the performance of it.
So..... I suspect this has been going on in the oil-markets for a while, and
the prices will have leveled out related to the performance.

That is my GUESS. That is not the truth.

BTW:
The best way to save on fuel cost is...
.... not drive.
It is easy to drive 10% less. Try it.
It is the truth.
Ehm.... oops!

Good luck.
Richard.

gerry wrote:
Sounds like about the same prices they are paying in California.

If your owners manual says 91 RON, you should be OK with regular. Pump
octane is RON+MON/2. RON is the higher of the two numbers in the
numerator and is sometimes used in other countries as the pump octane
displayed, hence it being quoted in your Volvo manual.

You can figure this out for your own situation yourself. Run a few
tanks of regular, then a few tanks of midgrade over the same conditions.
Keep track of your mileage and fuel costs (forget the # of gallons, it
doesn't matter). Assuming the engine does not knock or ping, make the
calculation for miles/$ instead of miles/gal. If you do better with the
midgrade repeat the experiment with premium vs. midgrade.

Who cares what the consensus is? Do you only vote for the projected
winner in an election? Can't you form your own informed opinion?

--
-Fred W

"gerry" <notforgenerause (AT) nospam (DOT) com> wrote

Then you should run it on the 91 stuff. Is that considered premium?

In the UK we have a different scale, ordinary unleaded is 95 RON, super is
97 upwards. You can buy 102 RON.

Hmm. Octane is the opposite of cetane in diesel. The higher the octane,
the harder it is to get the fuel to burn when compressed - which means you
can squeeze it harder for a bigger bang.

A higher cetane rating in diesel means it will burn easier when compressed.

Ignore him and try it yourself.

Generally, turbocharged cars like higher RON ratings, 'cos the fuel:air
mixture can be squeezed harder before it detonates. Pre-detonation is A
Very Bad Thing, also called pinking. Saab donks for the last X years, where
X is many have had a knock sensor that adjusts the ignition and reduces
power to avoid pinking. If you have a turbocharged Saab petrol engine and
you run it on a lower RON fuel, it'll produce less power or damage itself.
Run it on higher RON stuff and it'll produce the most it can, subject to
tolerances / ignition curves.

Not put especially scientifically...

That Bill Wattenberg is an idiot?

As Fred says, who cares? Suck it and see. But, if your handbook says 91
RON and you try 87 RON, you _may_ invalidate any warranty, but I don't know
of a modern-ish donk that could damage itself like this, merely run like a
three legged cat (i.e. lumpy and not as good as it should). :-)

--
The DervMan
www.dervman.com

DervMan wrote:
I normally use Shell Optimax in my 1993 9000CSE 2.0 LPT, 131k miles,
but the station on my route was closed for 3 months, then I used Morrisson
supermarket fuel (regular only). The engine was OK but not sparkling,
there were occasional flat spots which I put down to maintenance, filters
etc. Recently changed back to Optimax, and it feels like the engine has
been 'cleaned up' as it runs smoother and more consistently. Apart high
Octane, quality fuels also contain cleaning agents. Exhaust systems used
to be something which lasted for 3 years or so, but I'm really surprised
that the exhaust hasn't failed for 6 or 7 years since a box was last time
replaced. Wonder if that may have something to do with better fuel quality?

http://www.thorneymotorsport.co.uk/t..._Results.shtml

Check the above link out - is fairly imformative

Mickx


On 6/4/07 10:53, in article 461618DA.A45165A (AT) size-nospamhere-fitter (DOT) com,
"johannes" <johs (AT) size-nospamhere-fitter (DOT) com> wrote:

Mick x wrote:
The same as the pdf you posted, thx. (But better not post pdf here).
The performance aspect is just one part of it, though in practical terms,
I think that quality fuel is healthier for the engine.

I fully agree. I use V Power in our Areo Conv with Hirsch upgrade and Audi
A6 Quattro 3.2 FSI and notice the difference.


On 6/4/07 15:39, in article 46165C0E.A562AE9 (AT) size-nospamhere-fitter (DOT) com,
"johannes" <johs (AT) size-nospamhere-fitter (DOT) com> wrote:

Gerry,

FYI, and since nobody has mentioned it yet, 91 RON is about the same (within
1 octane point) as 87 AKI octane that your local gas station is pumping as
regular in Canada. You might get better acceleration and gas mileage with
higher octane, but if you don't need the acceleration and your engine spends
more than a bit of time warming up because of cold temperatures, the low
octane fuel is more economical. Wattenberg might be a bit off in the
details (probably to simplify it for his radio audience), but I agree with
his general philosophy. If you had an AERO, I might adjust my answer. That
is were Wattenberg's "generally speaking" part kicks in.

Walt Kienzle
1991 9000T

"gerry" <notforgenerause (AT) nospam (DOT) com> wrote

gerry wrote:

Actually the higher the octane rating the less the thermal enrgy in the petrol.
Yet it goes quicker ! Funny that isn't it ?

Don't listen to any jerks who tell you to ignore the manufacturer's
recommendations btw - no matter how many PhDs they may have. Foolishness knows
no bounds.

Graham