Thread: Hi Octane fuel

the higher the octane the more bang you get for your buck . I think normal ulp is 91, ethanol is 94 and premium is 98 . It does make a difference but for premium up pay through the nose for it and ethanol is normally 4 cents cheaper than ulp . Hope it helps

it could just be that your timing is out.

cheers phil

the higher the octane the more bang you get for your buck

I wish it were so!
Generally Octane only refers to the ability of the fuel to resist "knock" on a test rig.
The oil companies claim that their 98 octane fuels are more dense therefore give better mileage.
This may be so, but I reckon would only be on an engine with closed loop feedback, which would lean off to 14.7 :1 or whatever is set, if the denser fuel showed a lower AF ratio at the sensors.

Their claim of better performance only really applies to engines with knock sensors which retard if they hear knock. If they are fed high octane fuel, the computer advances to the maximum programmed extent if no knock is heard, thus giving better power and economy.
An old engine is so crude that little of this would apply.
In fact I found when I tried 98 in my 3.9 14CUX, that the engine stalled just before becoming fully warm, as high octane fuel is less volatile than low octane fuel.
Regards Philip A

Originally Posted by PhilipA

I wish it were so!
Generally Octane only refers to the ability of the fuel to resist "knock" on a test rig.
The oil companies claim that their 98 octane fuels are more dense therefore give better mileage.
This may be so, but I reckon would only be on an engine with closed loop feedback, which would lean off to 14.7 :1 or whatever is set, if the denser fuel showed a lower AF ratio at the sensors.

Their claim of better performance only really applies to engines with knock sensors which retard if they hear knock. If they are fed high octane fuel, the computer advances to the maximum programmed extent if no knock is heard, thus giving better power and economy.
An old engine is so crude that little of this would apply.
In fact I found when I tried 98 in my 3.9 14CUX, that the engine stalled just before becoming fully warm, as high octane fuel is less volatile than low octane fuel.
Regards Philip A

So you just manually advance the timing and make the most of the high octane fuel

Thanks Phil,

I have no idea what "closed loop feedback" is or "knock sensors", but I'm guessing none of this would apply to my basic 6 cylinder Landy?

Thought it was too much of a coincidence, maybe it was just wishful thinking. I've also noticed it seems to run better in colder weather? Any substance to that do you think?

Thanks for your input, much appreciated.

Originally Posted by PhilipA

I wish it were so!
Generally Octane only refers to the ability of the fuel to resist "knock" on a test rig.
The oil companies claim that their 98 octane fuels are more dense therefore give better mileage.
This may be so, but I reckon would only be on an engine with closed loop feedback, which would lean off to 14.7 :1 or whatever is set, if the denser fuel showed a lower AF ratio at the sensors.

Their claim of better performance only really applies to engines with knock sensors which retard if they hear knock. If they are fed high octane fuel, the computer advances to the maximum programmed extent if no knock is heard, thus giving better power and economy.
An old engine is so crude that little of this would apply.
In fact I found when I tried 98 in my 3.9 14CUX, that the engine stalled just before becoming fully warm, as high octane fuel is less volatile than low octane fuel.
Regards Philip A

I had the timing done a few weeks back, but will wait til Tony returns from the UK to do it again! I too thought it may have had something to do with the timing ...

Thanks Phil

Originally Posted by discowhite

it could just be that your timing is out.

cheers phil

Originally Posted by Panda

I had the timing done a few weeks back, but will wait til Tony returns from the UK to do it again! I too thought it may have had something to do with the timing ...

Thanks Phil

Advance it till it pings, then back it off a touch

Hi Mick,

I had a look at the manual which reckons the timing should be 2 ATDC with 90 octane, 6 ATDC 85 & 2 BTDC with 83. All very confusing. What's the difference with ethanol? I thought ethanol was the same as premium (yes, I know, showing my ignorance but hence I seek all your expert advice!)

So what should the timing be set at for premium? Are different premium petrols (e.g. Caltex, Shell etc) all the same octane levels, or are some higher or lower?

What does more "bang for your buck" mean? Does that mean it fires/ignites better?

Thanks

Originally Posted by wannalandy

the higher the octane the more bang you get for your buck . I think normal ulp is 91, ethanol is 94 and premium is 98 . It does make a difference but for premium up pay through the nose for it and ethanol is normally 4 cents cheaper than ulp . Hope it helps