Thread: High Octane

The Key point here is "when i go on a longer trip". This is why you are getting increased mileage despite the larger load, not the higher octane juice. If your car is designed to handle standard 91 puttin 95 or 98 in it isn't going to give you any effect beyond placebo. IF your car has been tuned to recognise different quality fuels and adjust the air/fuel/ignition mapping accordingly there is most definitely a benefit to forking out the extra coin.
Should I use premium petrol? — Auto Expert by John Cadogan - save thousands on your next new car!

FWIW I run 95 in mine day in day out

Octane boosters definitely work but different brands yield different results, in a modern standard car I would have thought they should still make a difference though.

I have seen a before and after in a friend's car running with 98 octane and 98 plus octane booster, with the booster added the hand controller for the ECU logged a lot less engine knock events and the car pulled much harder.


I generally run 95 in a plain Jane car, running 91 in a modern car won't really do much, cars these days are pretty smart so the computer stops anything bad from happening.
There are supposedly more cleaning agents in the premium fuels though, not sure what effect these have. An injector clean isn't all that expensive anyway.

Agreed, and for the premium you pay for the detergents, a bottle of over the counter cleaner such as Wynn's spitfire will do a better job far cheaper than the cleaning effect of premium fuel.

No question that big power can be had with higher octane, just look at some of the results being had with E85, but the car needs to be setup specifically to take advantage of it. Myriad knock sensors and the like reduce the impact of poor quality fuels that we have in Aust. Octane boosters can work alongside them and reduce the number of events but don't expect 'night and day' performance results because of it in a car with a factory ECU

Yeah, e85 is a weird beast, it has a lower calorific value than petrol but you can get a lot more power from it if the car is optimised to run the stuff.

Sorry, I was referring to an ultrasonic injector clean, they give you a before and after flow rate comparison'and don't cost the earth.
I've always been a bit scared of the bottle injector cleaners, they remove carbon and that's what the brushes in the fuel pump are made from, I'd love to know if it shortens the fuel pump life. However I guess if the premium fuels do it over time that additive would have a similar effect, so I guess my concerns are probably nothing to worry about.

The difference between longer trips using 91 and 95 is about 2l per 100km,

In dollar terms that , according to my arithmetic gives an advantage to 95
of 70c per100 km.

I always use 98. I have a Jap import Honda (1990 CRX) which which needs at least 95, any less and the power goes down.

Higher octane fuel means the engine can run a higher compression without knocking. You don't get more power from the fuel itself, you get more power because you can cram more air in the cylinder for the fuel to burn in.

Originally Posted by Ubernoob

I've always been a bit scared of the bottle injector cleaners, they remove carbon and that's what the brushes in the fuel pump are made from, I'd love to know if it shortens the fuel pump life.

If you're getting fuel flowing through the motor brushes, you have much bigger problems to worry about...

Originally Posted by elanjacobs

If you're getting fuel flowing through the motor brushes, you have much bigger problems to worry about...

I don't see why, I thought most in tank pumps had the fuel cooling the brushes?

Originally Posted by Ubernoob

I don't see why, I thought most in tank pumps had the fuel cooling the brushes?

Didn't know that, I figured they'd want to keep the fuel out of the power side