kovac21

I looked around and no answear did anybody notice that when you put higher octane level gas such as 93 94 that you geet significantly less kms the you do with say 91?

I did this test a few time and results are always the same
91 octane= around 500kms (give or take a few)
93 94 octane=around 415-430kms (give or take a few)
Driving style approximately the same.

Try it and let me no Thank you.

G37Sam

That doesn't make sense

Octane number is only a measure of resistance to detonation (knock), the injectors are still injecting the same amount listed in the fuel tables anyways

hispeed-lowdrag

iTrader: (7)

that statement is completely unsupported.

by only doing a couple "rounds" of testing that is not nearly enough to say that it happens. it should not matter anyways, the difference in octane wont effect the distance you get on a tank

SM_Shadowman

There are too many other factors that play into your mileage in order to test that without using some kind of controlled lab setting. Traffic that varies from day-to-day, where you drove, tire pressure, wild turkeys crossing the road, wind, weight of the car's contents, and so forth.

But otherwise, like the others said, octane should not affect mpg.

mw09g37

iTrader: (3)

Well I've seen cases of lower octane causing lower fuel eco. I think it's been shown somewhere than the G-VQ actually needs the high octane... or else power and efficiency both go down.
because the compression of the engine dictates what octane you need because said compression rate dictates the air fuel mixture (which can be adjusted by the ECU) a lower octane in a high compression engine results in slower compression which the ecu will turn to using more fuel to increase compression. which results in your car running rich.

... I think. cause the ECU is pretty dynamic, it will modify air fuel on the fly(to a certain degree of control) to make the car operate within within spec limits. the only differences between a factory turned and a aftermarket tune is where that air fuel mixture limts are.

so in a nut shell if it's pinging, your car is going to use more fuel to accompliish the same "work" from a lower octane, than you would from a higher octane...

but you have to admit tho, we US owners only have 91 octane. so we'd never actually use 93... so our engines are tuned to do as such... But I have heard of car testers that have used octane boosters in the G and didn't see much improvement, than for say... the GT-R

but yeah the marginal increase/decrease in fuel economy could've influenced by a ton of factors, I mean using your A/C for 50% of your travels could've made that difference. on top of tire pressure, oil viscosity, air tilers, throttle, aerodynamics at certain speeds speeds there's really no way to accurately say you have marginally better/worse fuel economy, without controlling those factors.

kovac21

Well i understand all of that if there was a differance of arond 10-20km then it would be ok right, but a differance of around 70-80km it dosnt make a lot of sense.
And i had the car for almost 2 years now and its been doing that since i had broke it in.
Dont get me wrong i dont really care about those km hahaha its just strange and i was woundering if any bodys car does the same thing thats all.

hispeed-lowdrag

iTrader: (7)

I've had differences of anywhere from 20ish miles to around 100 miles before, trust me it has nothing to do with the octane

mw09g37

iTrader: (3)

lol the gut shot post will always be a little harsher than the intention.

but at the end of the day, i mean there isn't much point of reference cause I think only Texas has 93 octane... and I'm not about to throw in 100 octane just to check... lol (6.50/gal)

i'd be a bad point of reference too... I took a 60 mile trip, (120 round trip) and my car (after about a week of driving) is approaching empty. I'm only going to get 315 out of that tank, (18mog yo! for 80% highway... lol )

hispeed-lowdrag

iTrader: (7)

I've used 93 octane tons of times...in plenty of other states than texas

mw09g37

iTrader: (3)

ok ok ,

then nowhere in CA do we ever see 93... lol I think it's for the west of the mississippi deal except for texas.

SM_Shadowman

I think that's a different scenario than what the OP was referring to. The high-compression VQ engine requires a minimum of 91 or there will be a greater chance of detonation (knocking). The knock sensor will adjust engine timings accordingly, which probably would affect power and even fuel economy, etc.

But using more than the necessary octane --for any engine in any car -- has never been shown to be beneficial in any way. Here in MD some gas stations have 91, some have 93, some even have both. But as long as I'm using at least 91 there won't be any difference going higher.

mw09g37

iTrader: (3)

yeah i know. I actually wasn't using it to explain the OP's point. I was going for I haven't seen higher octane = lower fuel economy. but i have seen lower octane = lower fuel economy,

SM_Shadowman

gotcha. Makes sense.

mw09g37

iTrader: (3)

but yeah all and all, that fuel eco is really bad... what is that 260mi vs 310mi? for a 17.5 gal avg fill up? I'd be more concerned that your car has an issue to get 260mi.

kovac21

But did all of you ever consider that higher the octane is the faster it burns and cleaner it burns thus less kms then gas with less octane.
Just a thought haha