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better mileage with higher octane? - Page 3

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Posted by * on January 3, 2007, 1:51 pm




Which, of course, is modifying the car - NOT gaining better mileage by
simply adding high octane gasoline...

Posted by digitalmaster on January 3, 2007, 2:21 pm

most vehicles have a knock sensor and will try to constantly adjust the
timing.If you use higher octane fuel the ecu will advance the timing
further.The question is will the added mileage make up for the price

Posted by news on January 2, 2007, 8:15 pm
 Eeyore wrote:

but only if the computer calls for more timing with higher octane.
If your computer calls for a max of 35 degrees and you can reach that on
  regular gas, 91 won't do anything.

That said, I have a Trans Am that will ping if you put in anything lower
than 91.  Manual says so, and I accidentially put in a tank of 87 by
accident.  Stopped 50 miles later and bought a shot of octane boost and
then filled up again at 1/2 tank to stop the pinging.


Posted by Eeyore on January 3, 2007, 12:29 am

news wrote:

Saab's Trionic ECUs will deliberately advance the timing until the engine *does*
pink intentionally so. And much much more besides. They even use spark plug
ionisation levels to determine mixture richness ( on a per cylinder basis ) !

They're probably the most advanced around. Many cars have clueless ECUs by
comparison. So it does depend hugely on the car.


Posted by * on January 3, 2007, 1:55 pm

Which "octane boost" did you buy?

104+ used to say right on the can that it "...enhances the octane
effect..." by cleaning carbon out of the combustion chamber - thus lowering
compression and knocking.

IOW - It didn't INCREASE the actual octane of the fuel, it simply DECREASED
the need for higher octane caused by higher compression pressures created
by carbon deposits.

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