Modern Fuels

[Big G]

So during the lock downs fuel became really cheap, so I thought I would treat my hilux ute to a bit of 98 octaine as it was just over a dollar a litre. It has a 3RZ in it and goes pretty well on 91 octane getting about 10 litres/100. I was disappointed to say the least when my economy didn't improve and I felt no real increase in power. I was also running it in the Princess' 4k powered rolla she was not impressed either.  I did a quick calculation using the normal cost of the 98 and over a year I would be looking at about $600 more than if I was using 91. My question is are these higher octane fuels of any real benefit?

 

[coln72]

Only if your car has knock sensors and can tune itself to suit the fuel. Or with the rolla you may be able to bump the timing up a bit.

Some say that 98 has additives that can clean your fuel system .....

[Banjo]

Best advice I've recently read !

https://www.mta.org.nz/motoring-tips/91-or-95-or-98-octane-petrol-which-to-use/

Cheers Banjo

[altezzaclub]

They will lower fuel consumption, which I watch pretty carefully. Sadly the half a L/100Km it will save you is never enough to justify the very noticeable extra cost, so I settle for United's 95octane.

Like you, I can't feel the difference, but those long 500Km runs over the same roads to the farm give me pretty sharp figures.

Edited July 22, 2020 by altezzaclub

[ke70dave]

You set your expectations too high.

[Taz_Rx]

I depends a lot on the car and the market it was designed for also. 

My ex once bought a Peugeot 405 mi16. She ran it on 95 and used to get around 500km from a tank. Switched to 98 and started getting over 800km to a tank!! Should have known better from the start being a euro, but this was just as 98 was becoming readily available. 

My Caldina is also very specific about only running 98, being a Japanese import. 

[Big G]

My expectations were fuelled (no pun intended) by petrol company hype and advertising. I will go back to 91 and monitor performance and consumption to see if there is a difference. Thanks for your input guys as always it is good to get opinions of the rolla gurus.

Cheers

G

[Taz_Rx]

Oh and fyi, I don't run my 13b bridge port on anything more than 91 because the compression and timing doesn't justify anymore! She's an old school IDA job. 

[ke70dave]

I work for a fuel's company and we love a good marketing campaign. The additives from a cleaning perspective have some merit. But any efi system basically pre ~2005 doesn't have the smarts to take advantage of additional octane over what it was originally tuned for. My e30 (1985.... but on megasquirt) I have tuned it on 98 (admitedly not on any dyno just by the feel of the pants). And I did put in 91 once and it certainly didn't like it that much. I mean it drove fine but the economy wasn't there or the throttle response. When you start playing with tuning engines its amazing the difference a degree or two makes. And this is how modern ecus take advantage of higher octane, i believe they actively increase timing slightly and listen for knock. Old ecus tend to have a maximum present timing and then just reduce that if knock is detected.

Edited July 23, 2020 by ke70dave

[LittleRedSpirit]

Ive got the 2az tuned on 98.  I want extra knock resistance because its on itbs that suck in hot air.  Have run it on 95 and 91 before with only a small loss of torque detected on the 91, with no tune adjustments made.  Its nice to know I could buy any available fuel in a pinch to get home.  Im sure if I clipped the timing slightly at peak there would be no long term differences to worry about.  Unable to report economy as Ive not run enough of the lower octane fuels.

[Big G]

So I have run about 6 tanks of 91 octane through my ute since I last posted and I can report that there was no noticeable difference in performance and almost no difference in consumption compared to the 98 octane. So for me it is a no brainer  91 octane all the way. I may treat her to the occasional injector treatment to keep her innards clean.

Cheers again for all your input.

G