better mileage with higher octane?

is there any truth to the statement that using a higher octane gasoline will result in better gas mileage? I understand that it may have other beneficial properties
ie. anti-knock, acceleration, etc..
how would one calculate such a statement?
for reference, I usually fillup between 16-20 gallons, regular gas is 87 octane, supreme 92 octane and in our area the price difference appears to be about 20c-30c between regular and supreme.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

will result in

properties ie.

Dont worry about calculating anything. Octane rating has no direct relationship to gas mileage. Antiknock properties are the key.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

and just what do you think Octane rating a measure of?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

gasoline
The octane rating is, just as I said, a number related to antiknock properties.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@nospam.nix wrote:

And good anti-knock properties ( higher octane ) allow the ignition to be advanced which *may* improve engine efficiency. It pretty much invariably improves performance.
Graham
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
* wrote:

I don't understand your point.
You can't just advance the timing willy nilly. In any case the ECU should control it and any advantage will be gained automatically.
Graham
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Depends on the ECU. Some can be "chipped" for more advance.Some OBD2 boxes can be "reflashed" Some that still have a distributor can have the timing physically advanced. On some you can adjust the cam sensor to provide more advance. On most, it's pretty well "cast in stone"
--
Posted via a free Usenet account from http://www.teranews.com


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote

With a performance chip set.......sold at any rod shop. And while you are there pick-up your turbocharger kit....and if you want to use premium switch to bi-turbo.

-
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote

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 difference?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Ray
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Graham
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
news wrote:

No ECU ? What year is that ?
Graham
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It doesn't matter if the engine is computer controlled or not if timing operates is open loop (no knock sensing).
The early 90:s non-turbo EFI:s I know does not have knock sensing and will happily ping without having a clue.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eeyore wrote:

Absolutely could not be more WRONG here. I race(d) in a class that limited compression to 9.5:1. We could run any fuel we wanted, and time after time, people would put race gas (Sunoco 110 or Turbo 110) then have to crank their ignition timing way up only to come close to getting the same performance that they did using 92 octane pump gas.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
51_racing wrote:

That's hardly typical though. I thought we were talking about road cars ? Also modern cars don't have manual timing adjustment., the ECU does it.
Graham
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eeyore wrote:

His point was that if the engine was optimized for lower octane fuel then you have to resort to work arounds like bumping the timing way up with little if any bennefit. There are no absolutes but it has been my experience that the higher octane fuel has a slower flame speed for a given temperture/pressure. Increasing the compression ratio will increase the temp/pressure. Without the compression increase you resort to advancing the timing to get the temp/pressure back up where you need it. But that works against you because the engine has to overcome the rise in cylinder pressure before the piston gets to TDC. So even if the ECU advances the timing to take advantage of higher octane you get little if anything extra for your money. If you have a turbo you can crank the boost up and make more power, but that's not the same thing as mileage, which is what this thread is about.
Bruce
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
if it help anyone at all my camaro on regular gets 24-25 mpg and pings and what not and on higher octane gas it gets 30-32 and never pings and seems to run better but thats just my car my dads built 350 in his s10 gets 14 mpg on regular and 15 on higher octane but it doesnt seem to run better so i guess it just depends on your vehicle.
--
rscamaroboy89
------------------------------------------------------------------------
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
rscamaroboy89 wrote:

Makes perfect sense. If you have a Camaro that gets that kind of mileage, its obviously an LS-1 or LT-1 with full digital engine management and knock sensors, plus a pretty high static compression. The engine managment system is having to pull back the timing to let the engine survive on regular octane gas, but can use its optimal settings on premium. An old carbureted HEI ignition 350 can't tell the difference in fuels because it doesn't have knock sensors and digital engine management. You could *manually* set the timing up to use premium, but then you couldn't run regular at all without risking damage.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
| The octane rating is, just as I said, a number related to antiknock | properties.
Wikipedia says lower octane petrol usually produces less heat , this I find true in BP's RON92 compared with RON97 : both my mitsubishi 4G15P & honda F20A ( original cr 9.2 & 9.6, both have improved cooling via copper wires ) can use RON92 , esp in humid air here & on flat land ( no towing / climbing ), but RON92 produces less heat ( & so torque ), so its 1.56% lower price cannot justify 2-4 % less torque. My brother's mitsubishi 6G72 ( cr is just 9 ) needs just RON92 per owner's manual, but he buys RON97, & I agree as wise.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@nospam.nix wrote:

Precisely. Just think about it -- at one time, octane was increased by adding lead compounds. Why would lead increase a fuel's energy?
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form snipped-for-privacy@prodigy.net.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.