Ran several Scirroco's years back & had a gentleman prove that premium is worth my extra $ at the pump. His instructions were to carefully calculate over 5 tankfulls the mileage of Premium vs Low-test. ( Sunoco 94 vs 87 in this case. ) Turns out that it clearly paid back more than 1/2 the price difference in better mpg. Technically it has been explained to me by several different sources that Premium fuel with higher octane has a slower (less prone to detonating) burn path. This is important in millisecond timing of the gas expansion in the combustion stroke. Consider that when your crankshaft throw is half way between TDC and BDC you have the most torque applied by the downward force of the piston. If your gas expansion is to quick and mostly expended by the time your piston reaches this area you loose power-making potential. In short, less throttle is needed to extract equal power. The detergent factor is a bonus and with Castrol Syntec thrown in for good measure I've seen some high mileage vehicles (Bikes & cars) with extremely low wear.
The downside is that the differences may not be as noticeable in a carb drenching fuel down the throat of an older N/A V8.
As for the original question the best gas in Ontario Canada is Sunoco 94/Sunoco91/Shell91/ & these are what we use almost exclusively. The worst is by far Esso....I would near walk as put it in any vehicle!!!
Cheers
TheCounty

 

The lowest octane in Sweden is 95, im going to try Shells VPower (98 premium) to see if MPG gets any better. I doubt it..

 

This is a common misunderstanding. The octane rating of gasoline has nothing to do with how 'fast' it burns, it is an expression of how resistant the fuel is to detonation. Perhaps it would be more appropriate to think of this as the 'stability' of the fuel- in the same way some explosives are easier to ignite than others.

Fuel in Sweden or anywhere in Europe is rated on the RON scale which no longer exists in North America. We use the AKI rating scale.

95 RON is equal to 89 or 90 AKI
95 RON is equal to around 93 AKI.

What does Jag recommend for your car?

 

Agree fully that "octane" is a value assigned to a fuel's resistance to premature detonation.... however if Mikey took the time to read what he copied, he would have noticed that it was not stated that "octane" meant slow burning but that a "slower burn path" is a property of a higher octane fuel. Suggest google the phrase "flame path propagation" for some interesting reading.
Cheers
TheCounty

 

I'd like to see the sources of this statement- Google does not bring up anything credible that supports your contention but does in fact bring a multitude of links that disassociates burn path velocity from the octane rating of a fuel. It's also incorrect to state 'premature' detonation as it infers that there is an appropriate moment when detonation is acceptable or desirable.

On another note- my first new bike was a red '73 Commando, frame number 220606 purchased in Feb. '73 from Firmot Motors in Montreal. I've always wondered what happened to it.

 

Premature detonation is common synonym for "knocking" & what was meant, sorry for any confusion.
Also, I am not talking "Racing" fuel for high HP applications. "Best" to me, indicated for the average chap day to day.
Must admit that Whitfields answer (see below) of "both" made for a bit of pause (and laughter, as where this can lead discussions), and yes I will certainly agree on the info for the opposite in respect to "race fuel".

Not much in the way of verifiable data when googling this topic but a lot of forum chat, most of which revolves only around peak horsepower. A quick scan over some of this topic did turn up mention at Whitfield Oil. They also manufacture race fuel and comment ..
“There are some high octane gasolines in the marketplace with fast flame speeds and some with slow flame speeds. It depends on how they are put together.”
This alone creates the equivalent to comparing apples to oranges with people using regular and premium in different areas! Thus the never ending forum debates.
Also in regard to Whitfields, their racing fuel is of a high flame speed because...
“At 6000 RPM, each spark plug fires 50 times per second. That's a lot of combustion processes happening in a very short time in the same combustion chamber. This is why racing gasoline need to be capable of burning fast. In your daily driver that may not see the top side of 3000 RPM, flame speed is not as critical. In a racing engine, everything is happening much faster, and in a bigger way because the throttle is wide open. “
Iqlearningsystems on racing fuel states this piece better than I,
“BURNING RATE is the speed at which a fuel burns and releases its heat energy. At higher
RPM’s there is less time for fuel to burn, so racing fuels tend to work better if they have a rapid
burning rate. If a fuel can be almost completely burned by the time the crankshaft is 20 degrees
after TDC (Top Dead Center) on the engine power stroke, peak horsepower and engine
efficiency are realized.”
Considering daily driving at well less than 6,000 rpm (ie 3000 rpm max avg, much less in town) . Time for combustion being doubled as rpm comparatively being halved would indicate that for efficient use of fuel & resultant higher mpg that a “slower” flame rate would put the maximum cylinder pressure at the most useful point in crankshaft rotation.
This would in effect explain my results. Other opinions welcome but I still respect this explanation for the results I have seen. However I will definitey revise my phrasing to the fact that higher octane fuels MAY have a slower burn rate and in reference to pump fuel only.
Now the bike side of me is screaming to get out....
A Commando for a first bike!!, at the time that must have been frickin' awesome. Kinda like giving a young fellow an XKR to learn to drive in.
As for locating it now...I'm not sure about Quebec, but in Ontario we have what is called a vehicle information package required for some years when privately selling/purchasing vehicles. Just present the Vin# to the License office and if it is in the system at all, for $20 you get a listing of all previous and current owner(s) & if leins are against. No cost if it doesn't show up. Hopfully similar in Quebec.
Cheers
TheCounty

 

Thanks for the references and info- I've read the Whitfield info before and it is accurate. What they're saying that there is variability in flame front velocity which can be 'adjusted' during blending at the refinery- but that it's not tied to octane rating. IOW- there is 'slow burning' low octane fuel and 'fast burning' high octane- and vice versa. The two parameters do not march in lock step.

Have a read here from another manufacturer of racing fuels:

http://www.rockettbrand.com/techsupp...ationships.pdf

In the 'real world' there's virtually no difference in burn speeds with pump gas and possibly more variation from one refinery/brand to the other rather than any other factor. Even this variable is unlikely- to achieve maximum power, the ignition timing would have to be advanced while using the 'slow' gas and reset back to original setting when reverting to 'fast' gas to avoid detonation. Not likely.

Regarding the bikes- I may try the system here before we move permanently to Ontario. I'd be very surprised if it's still around given the poor reliability and durability of the bikes from that era but you never know. I also had a '65 Sunbeam Tiger at the time and I'm sure my poor mother never slept a wink when I was out driving around. I presently have two bikes (having reduced the fleet from five just recently), one being a '79 Gold Wing that I've owned since new, and the other a '81 Honda CB1100RB, the only one in Canada AFAIK. My other toy is a '73 Corvette that I've owned since '89 and did a frame off restoration in '96. Fun stuff!

 

When I drive through certain parts of Alabama I like to use a brand called ENTEC. They have a 98 octane.

Other than that (which is rare) Shell.

 

When I drive through certain parts of Alabama I like to use a brand called ENTEC. They have a 98 octane.

Other than that (which is rare) Shell.

 

Maxjag, do you use ethanol in Sweden?