Octane rating vs fuel consumption

[Jigks]

Here in Australia we have the following readily available unleaded fuels with octane ratings of 91, 95 and 98.

My question is with a standard 6.2L that has not been tuned yet, is there any difference in fuel economy or power by using the higher octane fuel?

Has anyone done any comparisons and noticed a difference in either power or economy with a standard engine?

Thanks.

 

[pat247]

It has been said that the 411 hp rating for the 6.2L is with 91 octane fuel and it only makes 401 hp with 87. So to answer your question it would seem logical that it would make more hp with higher octane fuel since the computer is adaptive. I would like to see what kind of numbers it would get with 98 octane.

 

[Jigks]

That's interesting, I might try a tank of 98 as well but as I have only clocked 1400 km not sure if the engine is still loosening up.

 

[Icecobra]

The real question is what method do they use to determine the octane rating. You can use different methods and get different ratings. We in the USA (R+M)/2 method. In Australia your by comparison rating is: method RON 91-92, method MON 82-83 and method AKI 87. Each method performs a different test and yields a different result. You don't use the same standards as in the US and probably by the US test would determine your actually about 85 to 88 Octane in regular fuel. Your premium would yield about 90 to 92 Octane... For what its worth...

 

[MTF]

Like Icecobra said, it is different ratings.

In general there is a 4 to 5 point difference between the two methods.

So....Ron 91, 95, 98..... is like.....87, 91, 93 here in the states.

The thing to remember is they only make two different octanes, crap low octane and premium everything in between is blended.

 

[Ruger]

What Pat says is right out of the manual - there is a ten hp difference between regular fuel and premium fuel. We have relatively high compression engines, 9.8 to 1 if memory serves. The engine management system will slightly retard spark timing to compensate for lower octane fuel, hence the very modest lost of horsepower. It's very unlikely that you will be able to detect a difference of ten ponies in a 400+ hp engine unless you drive at wide open throttle a lot and have a calibrated backside. There will be no difference in fuel economy.

 

[The Macf]

Non US countries use RON. Your 98 is our 93 octane. Use that.

 

[Jigks]

Thanks for the clarification guys.

 

[KaiserM715]

There will be no difference in fuel economy.

Agreed.

 

[Harblar]

Actually, there will be a difference in fuel economy. When I first got my raptor I tried the three main fuel types we had in the area, 87, 89(10%ethanol), and 91. I kept track of the mileage for each tank (still do, though all I burn is 91 anymore) trying to drive the same type of miles on each one. I also made sure to run 3-4 tanks of the same grade in a row to allow the engine to settle into to it. After 6months it was pretty obvious that I could get an easy 50-60 more miles out of a tank of 91 than I could out of 87. The cost difference between the two was negligible even though a tank of 91 obviously cost more. The 89 was right in between the two others, but I opted to just use 91, as the cost wasn't that much higher and I ended up adding a tune and headers, etc... after that.

In the end, to each their own when it comes to fuel grades, but with everything we do to mod our trucks and how we run them, I can't understand why are people so obsessed with cheaping out on the fuel. Put the high grade in, mash the throttle, and enjoy!