Normal Or High Octane Fuel?

[fivebob]

its not detonation, its pre-ignition or 'pinking'

.... There's a difference?

Both are high speed shock waves created by spontaneous ignition under different condition.

Not quite, detonation does not usually refer to spontaneous ignition, just uncontrolled combustion from a normally ignited charge

[KinLoud]

Ewan (10k20v) had a 1997 250T Subaru Liberty wagon (2.5L N/A not turbo)
He worked at a place with a dyno and did an experiment.
On 91 octane the computer richened the mixture, also had 10 or 15kw less power, I guess because the computer detected knock
On 95 mixture a bit leaner, a bit more power
On 98 leanest mixture and best power

For this car it was cheaper per km of driving to run it on higher octane fuel.

Ken

[rollaholic]

yeah fivebob you are quite right, pre-ignition is not the correct term for what i was trying to convey pre-coffee this morning (any excuse)

i have always been under the impression that too low octane fuel resulted in an over-rapid burn of the AF mixture, and as a result the peak pressure problem you mentioned - rather than actual explosive events (detonation) outside of the flame front, generally caused by too-high combustion chamber temps / too-lean mixtures (eg too much boost) resulting in vaporised (explosive) gasoline rather than atomised (burnable) hence my attempt to differentiate between the two.

[Mr Revhead]

just remember that higher octane doesnt ALWAYS mean more Ks/power.
for example my 2000 corolla.
ran it for several tanks on 91
then several on 96.
zero difference in Ks traveled.

[Dell'Orto]

No, generally only in vehicles that actually require it. I know my KE70 wagon made zero difference in fuel economy or power with 95 or 98 over 91 octane.

[strx7]

its not detonation, its pre-ignition or 'pinking'

.... There's a difference?

Pre Ignition DESTROYS engine components ie Bends conrods, lifts cylinder heads etc etc

[tsoob]

i only use 98. if its a shitter then ill put 91 in it but in my cars 98 only.

[flygt4]

i've run all grades of fuel on my caldina GT , which has the factory trip computer for fuel economy and av speed etc. it conveniently has a similar engine, although a later version, to the original posters. I can't vouch for the accuracy of the trip computer but since its comparing the same information i'd consider it acceptable for direct comparison.

91 is not worth running, runs like a pig, and gets shocking economy. runs at about 10-11km/L at best.

95/96 runs at about 11.5-13km/L (i think it measures this way round on caldina, correct me if wrong) so ~2km/L better economy than 91 and the engine runs really nice, feels like it has a whole lot more pickup.

98 is by far the nicest to put in, economy is the highest and the engine runs significantly better. runs roughly another 1km/L for economy, gets up to 14km/L , sometimes 15 on long trips.

I did sit down ages ago and figure it out and i found that 95 was the cheapest to run for everyday use, but that 98 was marginally better for long trips on the open road. I checked this over the course of the 2nd full tank of the rated fuel for similar types of driving too. the difference is such that if the wife puts the wrong gas in i can notice it when I drive the car next.

[Crampy]

Has anyone tried Gull Force 10 and compared that with 95 and 98?
What's it like economywise and how well the engine runs on it?

[Leon]

I had a EP82 Starlet (4EFE) without a trip meter, so I had a little notebook in the glovebox that I used to track fuel economy (because I like to know these things).

Going from 91 to 95 improved the fuel economy by 1.5km/l

So, not a huge amount, but a measurable change because I measured that over several thousand km on each fuel.