Octane Rating 91 or 98?

[losh1971]

Tried 95 in the VT and the only difference was it paying more for nothing.

i find it depends on the brand with 95. Caltex 95 has always got me the best economy. I tested BP, Shell and Caltex before I come to the conclusion.

 

[Mike Litherous]

Does the commodore that accepts e85 have an improved power tune from then factory?

It’s a pity that e85 is not more widespread.

I’m planning on an engine build for my old 635 bmw. I’m going to use an ethonol sensor with high static comp but just low enough where it can live on 98 as the fuel tank is not that large.

 

[monstar]

Does the commodore that accepts e85 have an improved power tune from then factory?

It’s a pity that e85 is not more widespread.

I’m planning on an engine build for my old 635 bmw. I’m going to use an ethonol sensor with high static comp but just low enough where it can live on 98 as the fuel tank is not that large.

Well yes but it is never mentioned. The improvment is in higher torque peak and average torque therefore higher average kW, but I don’t think it is tuned for peak kW as it can be.
What is the engine designation of the 635? Does the factory ecu and fuel system have the capacity to handle flex fuel or are you using and aftermarket ecu and fuel pump, injectors?

 

[commodoretouring]

I am interested to hear an expert opinion on this subject as it gets a huge amount of airplay/discussion/marketing as any subject in the automotive world!
My opinion is thus : 95/98 Premium Unleaded has a max. of 50 ppm sulphur v min of 150 ppm for 91...unless the engine is either tuned to achieve it's best on 95/98 , or has the knock sensor capabilities to adapt to higher octane fuels, there is no benefit. We have various Australian cars in the family & I suspect the Commodores don't respond significantly to 95/98 & GMH never made any claims to that effect .
The FG Falcon 4.0 litre 6 definitely adapts & responds in my experience & there are multiple sources to support that & the reasons why.. love to find out what a GM powertrain engineer says about the subject now that local production of all cars has finished....

 

[monstar]

I am interested to hear an expert opinion on this subject as it gets a huge amount of airplay/discussion/marketing as any subject in the automotive world!
My opinion is thus : 95/98 Premium Unleaded has a max. of 50 ppm sulphur v min of 150 ppm for 91...unless the engine is either tuned to achieve it's best on 95/98 , or has the knock sensor capabilities to adapt to higher octane fuels, there is no benefit. We have various Australian cars in the family & I suspect the Commodores don't respond significantly to 95/98 & GMH never made any claims to that effect .
The FG Falcon 4.0 litre 6 definitely adapts & responds in my experience & there are multiple sources to support that & the reasons why.. love to find out what a GM powertrain engineer says about the subject now that local production of all cars has finished....

We banned all experts years ago, arrogant pricks ruin a good story. Now we just get on with arguing.

 

[Mike Litherous]

Well yes but it is never mentioned. The improvment is in higher torque peak and average torque therefore higher average kW, but I don’t think it is tuned for peak kW as it can be.
What is the engine designation of the 635? Does the factory ecu and fuel system have the capacity to handle flex fuel or are you using and aftermarket ecu and fuel pump, injectors?

Hey. It’s an m88/3 with the ITB. I’m going to wrap the orignal engine matching numbers to the chassis on cotton wool and collecting parts for s38 with the 90mm crank. Depending on the cams I use will have at least 12:1 static comp. Using a standalone haltech sport 2000 which has flex fuel capability. Not sure on how much power but it should be north of 425bhp out of approx 3.9ltr only having to rev it to mabee low 8k keeping it relyable. Not many play with these engines. One recently with lower spec than I’m planning on made 387rwhp. If the dyno is legit it’s an awful lot of power from just under 4ltr naturally aspirated.

Back in the day 1980/1 they were making 470bhp of these engines with moderate comp and 9000+rpm.

I want to run both e85 and ron98. E85 being primary fuel and due to moderate fuel tank I want the ability to run ron98 to give some sort of touring range.

Hey chaps sorry for the hyjack

 

[Mick Feeney]

Do three tanks full of 91 and then check fuel usage and power and then 3 tanks full of 98 and do the same - make an educated decision. 91 will most likely be the more economical. I have access to cheaper 98, so that's all I use.

And I never use E10 or E anything fuels

I used 98 on the weekend going to Tamworth, the car ran like a dream and it did 7-2 onto the gauge. 2011 series ll 3 lt commodore

 

[Voodoo_SV6]

I used 98 on the weekend going to Tamworth, the car ran like a dream and it did 7-2 onto the gauge. 2011 series ll 3 lt commodore

My VF SII SV6 got 6.5l/100km as it's best ever economy. I did nanny the car to see how far it would go. Normal was mid 7s for my SW Sydney to Albion Park daily work drive