Anyone ever put anything higher than Octane 93 in their MCS? There is a place by me that sells 100 or 110 I think so tempted to try it...

Izzy

 

yes

 

Every article I've read has always said if you're using premium when your manual says you only need regular, you're wasting money.

So wouldn't this apply here too?

 

Yeah, unless your car is modded to need it and/or tuned to use it, you're wasting your money. I'm guessing James' car fits one or both of the above criteria.

 

If you got a custom ecu tune to run it, you would see a benefit, otherwise it's a waste of money.

 

Wik'a discussion of octane rating is pretty good . . .

http://en.wikipedia.org/wiki/Octane_rating

bullets

The octane rating is a measure of the resistance of petrol and other fuels to autoignition

{note RESISTANCE .... higher octane is harder to burn off}

Octane rating does not relate to the energy content of the fuel

It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily.

A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.

However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate (knock), that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor – a small piezoelectric microphone which detects knock, and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency.

 

... but doesn't the piezo-control unit-ignition timing gubbins also advance the timing to the same degree, based on the higher octane's greater resistance to knock? In other words, it retards the timing when it begins to detect knock with a lower octane fuel in the tank; doesn't it also advance timing when a higher octane is used? Seems logical that it would. My understanding is that the timing is constantly being dynamically adjusted (by all the sensors and electronic controls) to its optimum "just before it knocks" setting. Lower octane ---> retarded timing ---> less power ---> lower economy. Higher octane should mean ---> more advance---> more power---> better economy.

To a point, and within some limits, of course.

Now, my understanding is quite limited (mostly to '60s muscle cars and old British sportscars) and has been proven faulty many times in the past


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Yes but only to about 95 or so. You would need to increase the compression ratio to take advantage of higher octane. It's just a BIG waist of money for less mileage and lower performance. Of course people will swear by the placebo effect it causes when it empties your wallet.

 

Agreed - any gains would be minimal without some other expensive engine work. But on principle - you might gain a little with just the fuel, no?

Agreed again - you'd never want to drive around day-to-day with expensive high octane fuel in your tank - not worth it for sure. But for a track day or an autocross - maybe a hundredth or two difference? The difference between first and first of the losers...
BTW - wouldn't optimizing the high octane-advanced timing relationship result in better mileage and better performance? Even minimally...

Back in the dark ages, the drag strip crowd used to drain the gas tank in the '69 Camaro before their quarter-mile run and pour in about 5 gallons of avgas they'd purchased at the local airport (reputed to be the highest-octane gas you could buy back then - and the most expensive). Did it help their E.T.? Who knows? They thought it did. So - worth it to them for any advantage, however miniscule.


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Yes

 

Two posts... two words.

 

There is a reason you run premium in a turbo vehicle. And to make sure I don't step out of line it pretty much as has to with detonation.