Really feeling the placebo effect (put highest octane in the Mirage)

[Ares]

So the tank was way more than empty - more than likely running on fumes, and I bit the bullet: put the highest octane on her, 93?

After about 50 miles on the road, I feel like the engine is running AND sounding smoother. Also, there used to be a dip in power at 2k-3k or so RPMs and I don't feel it now. Lastly, the power on freeway pulls feel more responsive; more direct.

Should have dyno'd the car before. Maybe I'll keep using expensive gas til the prices go up and dyno before I switch back then dyno again after switching.

P.S.
Some cars have been proven to react better with high octane fuel. Mostly forcefed engines and or Fords. I remember the Ford/Mustang forums raving about a few HP just by switching.

Maybe it applies to the mirage too? I mean, the ECU and VVTI should be smart enough, even for our cars, no?

P.P.S
I'm driving up to dallas tomorrow and back on Sunday. Will report more useless observations.

[alex16]

Some cars are designed to recognize 93 and increase the hp with different timing/maping. I doubt the mirage makes any more hp from 93, but a dyno is the only true way to prove power increases, although it must be done at similar temps, engine temps, same dyno.

[Cani Lupine]

The octane rating doesn't have anything to do with power, but about how stable the fuel is. The lower the octane rating, the more readily it burns. Higher octane fuels are more stable and less likely to combust prematurely. The increased stability of higher octane fuel means you can increase the compression ratio further with less risk of detonation, or knocking/pinging. Using high octane fuel in a car that doesn't require it won't add horsepower, but you'll notice it run smoother.

[MetroMPG]

Engines with knock sensors tied to electronically controlled spark timing can become more efficient/powerful when running higher octane: with reduced knock, timing can be advanced which means higher effective compression (cylinder pressure).

Enough to feel in a 74hp engine? I dunno. Dyno!

[MetroMPG]

One othe possible factor: in some places that sell ethanol blended fuel, the premium/super grade doesn't contain ethanol and so has higher energy density. That's the case in Ontario anyway.

Will report more useless observations.

Funny.

[Ares]

Another useless observation:
When I'm lazy, I don't downshift or put the car into N til the last minute - sometimes even breaking to a complete stop. This morning, whilst getting donuts, I did the same thing and the car was limping forward - on its own. LoL.

Don't ask me. Just reporting.

The octane rating doesn't have anything to do with power, but about how stable the fuel is. The lower the octane rating, the more readily it burns. Higher octane fuels are more stable and less likely to combust prematurely. The increased stability of higher octane fuel means you can increase the compression ratio further with less risk of detonation, or knocking/pinging. Using high octane fuel in a car that doesn't require it won't add horsepower, but you'll notice it run smoother.

Like I said, it has been proven by some cars.

You and Metro seem to have the same explanation, but one claims it can and the other claims it does not.

[deleted user]

If it's more efficient you will see better mileage. The question is does your cost per mile go down?

regards
mech

[strawboss]

I have have run all sorts of small engines from tiny gas powered 2 stroke/4stroke radio control engines to 2 hp suzuki outboards and the 3 cyl smart and mitsubishi engines and found that the smaller engines are really affected by fuel quality, temperature/humidity etc.(a possible exception is my diesel fortwo)
The 3A92 having variable valve/spark timing can compensate more than my 2Hp suzuki or my 15Hp Honda but I'm not surprised that the "seat of the pants" meter noticed better performance.....now like another poster observed does the better performance and fuel economy justify the higher price?
I was having start/run issues with my Suzuki on regular pump gas that disappeared when I started using Shell Supreme that had no ethanol.

[Ares]

More could-be-just-my-mind-messing-with-me observations:

I swear that the engine is running so smoothly and much more quiet now. During idle, during cruising speed, during WOT, it dont matter; feels like new, softer engine mounts were put on and engine bay got some sound insulation.

Averaged 38ish MPG from manual miles/gallon calculation. However, the trips included constant 75-85mph and some stop-n-go traffic. Also, remember that I traveled through the hill country. Lots of hills and dips. Without the hills, with those speeds, I can imagine doing at least 40.

2 passengers maybe 320lbs max. Two duffel bags, and other junk in the trunk ~ 50lbs.

I'll keep putting premium for a month and try to get more accurate readings. Maybe find a sound meter for comparisons. IIRC there is also a cellphone 'dyno' app that I can play with.

[Minihaha]

[QUOTE=MetroMPG;28350]Engines with knock sensors tied to electronically controlled spark timing can become more efficient/powerful when running higher octane: with reduced knock, timing can be advanced which means higher effective compression (cylinder pressure).
/QUOTE]

The efficiency cannot be improved beyond the specifications.
If the engine is so out-of-whack it's implementing the ignition retarder on the lowest octane fuel (besides having bigger problems...) then I suppose it could "become more efficient/powerful when running higher octane." However if everything is running hunky-dory (as designed / specified) an increase in the supplied fuel's octane rating will do one thing: lighten your wallet.

To suggest otherwise is misinformation.

The timing will not advance beyond specified settings and give one's engine increased performance solely on the input of higher octane fuel.
But feel free to supplement your chosen oil companies coffers should you wish to do so.