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?

 

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 .....

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

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, 20206 yr by altezzaclub

You set your expectations too high.

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. 

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

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. 

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, 20206 yr by ke70dave

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.

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