98/91 fuel, how much difference?

[monkeywrench]

i agree 98 runs better i had 4wd and when i run it on 91 it wouldnt idle smooth worse fuel economy,than it did when i run it on 98 plus it ran smoother i actually tell my customers to run at least 1 tank 0f 98 every now and then as it acts like a fuel system cleaner

 

[DLFHUB666]

i agree 98 runs better i had 4wd and when i run it on 91 it wouldnt idle smooth worse fuel economy,than it did when i run it on 98 plus it ran smoother i actually tell my customers to run at least 1 tank 0f 98 every now and then as it acts like a fuel system cleaner

agree with the run 1 tank a month or week what ever but what im saying is there is no real benifit unless you get a tune to suit. an what kind of 4wd it may of had a standed tune that could recognise the differance between 91 / 98 where as the commodore tune dosent like i said above its not backed up by a dyno print out but they said a 2kw differance between 91/98 on a standed vz tune now if you think that is abenifit well keep buying it.

 

[Brett_jjj]

I wouldnt take any claims you read on the net too seriously.Theres claims that this is better or that is better.Theres thousands of them on there,most of it is just crap.Im going on what timing the ECU runs at,on whichever fuel, and the cost of the fuel over time.I know that the ignition timing that the engine uses when on 91 fuel is heaps lower,than when on 98, and the knock sensors detect knock way earlier on 91 octane whcih makes the ECU drop back to its lower octane timing table.When on 98 ,the engine hardly detects any knock,which means continuous running in the high octane timing map.This alone is one of the reasons why the 98 runs better.Especially if you have a heavy foot like me..If you seriously cant notice the difference between the two fuels,theres probably something else wrong with the car to begin with.

 

[DLFHUB666]

so your telling me that if you jumped in two identical cars an 1 had 91 an the other had 98 you could tell the differeance without your scan tool telling you that 1 has abit more timing advance than the other. doubt it. an with timing advance have you noticed on a hot day that the advance it a little bit less than on a cold day thats about the same as 91 vs 98 not really worth writing home about . but as you can see by the dyno read out i posted that if you get it tuned to 98 there is a considerable differance. anyway im over it . it just like ps3 vs xbox 360 everyone has there own side.by the way my car is tuned for 98 so no problem there.

 

[Brett_jjj]

Heat doesnt really effect the timing at all.I thought it would effect it a lot more than what it actuallly does.And I cant say this for every car,but Id guarantee that anyone who drove my car on 91 fuel,then 98 could easily tell the difference.And the timing difference between the two fuels does make a difference to how it runs.I do my own tunes,and Im always playing with the low and high octane tables for the ignition timing.A few degrees of advance makes a big difference to how the car runs.

 

[DLFHUB666]

Heat doesnt really effect the timing at all.I thought it would effect it a lot more than what it actuallly does.And I cant say this for every car,but Id guarantee that anyone who drove my car on 91 fuel,then 98 could easily tell the difference.And the timing difference between the two fuels does make a difference to how it runs.I do my own tunes,and Im always playing with the low and high octane tables for the ignition timing.A few degrees of advance makes a big difference to how the car runs.

sorry to keep going but you write your own tunes??? Im talking about a bog stock tune one from the factory not one that has been altered .so what your saying is you have altered a tune to better suit 98 which if you read my posts is what i have been saying the whole time to get the most out of 98 it has to be tuned.So yes i would probably feel the differance if i drove your car on 91/98. but i bet you couldnt feel the differance in a bog stock car from holden.

 

[Brett_jjj]

sorry to keep going but you write your own tunes??? Im talking about a bog stock tune one from the factory not one that has been altered .so what your saying is you have altered a tune to better suit 98 which if you read my posts is what i have been saying the whole time to get the most out of 98 it has to be tuned.So yes i would probably feel the differance if i drove your car on 91/98. but i bet you couldnt feel the differance in a bog stock car from holden.

As I said before in the above posts ,even when running a standard tune you can notice the difference between the two fuels..Of course a tune will take more advantage of the higher octane fuels,because you can add more timing advance to the timing tables.

 

[Daggy082]

Fuel never burns 100% in the combustion chamber so using 98 which burns better is obviously gonna burn the fuel more then 91... Thus making the car run better... It's as basic as that. This has come straight from a Holden mechanic who is my mate. So not like he is trying to prove anything or trying to get more money out of me...

 

[Bizmark]

Ecotecs are said to run a little better on 98, they sometimes ping on 91 under significant load so if you're having pinging problems on 91, try 95 or 98. If that fixes the problem then get the car tuned for 98 as well so you see a bit more power and more economy :thumbsup:

 

[sleepa]

I used to only run 98 Octane in my Turbo 180sx as when I ran 95 it would be noticeably more sluggish, especially between gear changes. Also I would notice a lot of power loss on really hot days.

However I have only ran 91 octane in my LS1 and have had no ill effects whatsoever. I don't need any more power for cruising around, and it is after all designed to run on it.
I'd run up to 95 on a standard tune but only use 98 when I get it properly tuned for it otherwise I don't see a point running 98.