Question on Gasoline Octane

[Raz]

Hi guys,

I just realized while pumping Premium Gasoline in my 07 G35 6MT, that I was pumping 91 octane, I remember it used to be 92 or 93 octane, I checked Chevron, Shell, Mobill and Union 76 there all 87 / 89 / 91, I live in California, is this normal in other states and is 91 Octane good for my car???

[G_whizz]

91 is totally fine... can't do it for you right now... but there is a HUGE discussion on what octane people use for their G's ... click the search and it will come up

Welcome to NICO!!!

[SVTCOBRA]

as long as it don't ping, you are

[Raz]

Thanks Guys, I was wondering why all these gas companies they reduced the octane to 91, when it used to be 92 or 93, I think they are making more profit.

Raz

[telcoman]

Thanks Guys, I was wondering why all these gas companies they reduced the octane to 91, when it used to be 92 or 93, I think they are making more profit.

Raz

You are correct. Gasoline companies do make huge profits on selling 92 or 93 octane. I have almost 40k miles on my 06 G35 6sp manual Sedan & have never used premium. Regular 87 octane is just fine. Never heard a ping and my MPG is between 23.5 & 24.5 MPG. Best mileage on a tank was 28,83 MPG on a trip to Florida from NJ.There are many strong opinions on what gasoline & oil to use on this site but as one who has been driving for over 40 years my advise is:1- Try regular 87 octane2 Change your own oil every 3k to 3.5k miles using SAE 5w-30 wherever it is on sale

In my opinion, I read many posts on this site of people throwing money away on vehicles that they are leasing and may not own after a few years?

If you are a young person, save the money on gas & oil & open a IRA or 401k plan. You'll thank me in 25 years.

Telcoman

[redhed]

in the good ole' northern plains where i live...amoco ultimate is still rated 92 octane and sinclair's high octane is 93...all the rest are 91...fwiw.

[joe603]

The G's ECU will compensate for lower octane, but you'll get reduced performance. So its ok if you stuck in the middle of nowhere...just use premium ASAP.

[Q45tech]

Refineries only charge 5-7 cents per gallon MORE for premium vs regular the spreads gets wide at the service station due to low sales volume of premium.

Less than 20% of US gasoline sold is premium yet it requires separate tanks and pumps, separate trips down the pipeline

[ugaexploder]

93 pretty much everywhere you go in georgia

right joe?

[Raz]

93 pretty much everywhere you go in georgia

right joe?

Lucky you.

[g35cuhlean]

Im from cali, i pump strictly only shell, chevron and 76 . all 91

U should be fine. We Cali resident dont have 92 or 93 unless we go to a race track.

[Tapper]

It always surprises me how few people really understand the gasoline we all depend so heavily on. So I'll toss out a few facts, just for grins.

Premium gas isn't premium. The additive packages in most brands of gasoline are the same (at a given time of year) whether it's 87 or 93 octane. Refiners do change the formulation based on expected temperatures, however.

Octane, in simplest terms, is a measurement of the lowest compression the gasoline can support (in a standard test motor) before pre-ignition occurs. The lower the octane, the lower the compression measured.

The "best" octane for a given motor, is the octane it was designed to run on - a combination of the motor's compression, spark timing, cam timing, piston shape, etc. If your motor was designed to run 87 octane, running 93 in it will cause you to lose power, not gain it.

ECU's can't measure octane. In the event you screwed up your combustion so far that your exhaust began to contain a lot more 0xygen, then it might try to adjust - but since the programmers assume you will actually follow their instructions on which octane to run - the ECU will try to reduce the oxy level through means which aren't very likely to return the performance lost (which won't be much, in any event). Although ECU's can adjust the spark timing, it's doubtful that this is the approach they would take (most simply increase the injector dwell time a little to decrease oxygen). Even were they to adjust the advance a bit, this probably wouldn't help, because it also pulls the cylinder pressure along with it - which is more likely to move the "point of maximum pressure" somewhere in the stroke that you don't actually want it. Net result - no help, or matters worse not better.

Switching to conjecture, I have to wonder what octane our motors were actually designed to run. A 10.5/1 motor can run anything from 86 on up, depending on other design factors. Has anyone actually measured this? It would sure be nice to save a few bucks at the pump, if the octane isn't needed. And there's a sneaking suspician in my heart, that says the Infiniti marketers said "premium car, so premium gas", whether the motor needs it or not.

[redhed]

well, all i know is that an '06 automatic g sedan recommends a minimum octane of 87....and an '06 automatic coupe is supposed to drink 91 octane...according to the owner's manual. yet, they are both rated the same hp/torque. hummmmm!!!!!!

[Q45tech]

If you analyse 93 octane in ATL Metro you will find it identical to 91 octane at sealevel stations. In a way California requires more honesty less hype.

In many States, Marketters are allowed to post what ever number they want on pumps as long as it meets the 600 and 900 rpm antiknock tests for pipelines.

Conventional Fungible [swapable minimum standard] Regular and Premium are the bulk of transports.

ATL being 1000' AMSL and NorthGA higher allows the 91 to perform like a real 93 as long as you don't drive much South of Macon.

Denver is the extreme case where 85/89 are the norm

Doesn't have a great validity to modern high compression engines.

Knock sensor systems react fast to decrease ignition advance and stop knocking so hard to hear or feel the tiny power decrease.

Most would never know it if a 20 HP reduction occurred as that would only increase quarter mile by 0.2 seconds

[clmays1]

All modern ECM's will adjust the ignition timing if the knock sensors detect any pining or knock (regardless of whether the driver can detect it). The exact algorithm for retarting timing and return advance varies from car to car. If you run 87 octane in your G35, odds are that when it is very hot outside your timing will get retard by the ECM to prevent detonation if you are doing any WOT runs. Running 87 octane should not harm your engine as it was design to prevent this; however, pulling timing out will reduce torque. You would never notice this at mild to moderate driving.

Here is NC we have 93 octane everwhere and can get 100 octane at the pump at certain stations in major cities.

[eastvolt]

well, if i run my 2004 sedan on 87, it runs like absolute **** and constantly pings.

[slobo7x]

Well this car isn't FI from factory so the risk of detonation is lower compared to turbo charged vehicles. Octane rating is basically an Anti Knock Index, as mentioned. Higher octane fuel contains more oxygen and therefore burns easier inside the combustion chambers..

I have seen 3.7 liter american engines that recommend 87 octance. I've also seen 4 cylnder japanese cars recommending premium octane from factory.

As a general rule of thumb, i would not recommend running the lowest octane rating on a 3.5 engine especiallyif you plan to keep the G for a longer time.

[smockers83]

It doesn't matter what size engine you have, you could have a 5.7 V8 running a recommended 87. The reason for the higher 'recommended' octane on the G is because it has a high compression ratio. The higher octane allows the cylinders to achieve full compression at the point of combustion where as 87 would detonate earlier, so the computer has to change the timing to compensate. So what it does is ignite the gas at a less than optimal point of combustion.

It also doesn't have to do with how much oxygen is in the gasoline. Octane is an actual substance that is produced (the chemical term is isooctane). The higher the octane level, the slower and more controlled the burn is. On a 10.5:1 compression ratio without modern management systems, you would run 100 octane, but with engine management you can bring this down several points...hence the 91-93 octane levels aka premium. For Denver, and any other city in the Rockies for that matter, they don't need the 91-93 levels due to the elevation.

[mnotx]

Also, the higher the altitude, the lower the octane requirement. That is why the highest octane you can get around here is 91. Drive toward San Antonio (and drop in elevation) and you find 93 for sale.

Octane depends a lot on where you are. I use 91 where I live, but have to go with 93 when I am driving at a lower elevation to achieve the same results. Gas companies know this and adjust accordingly.

[gwoods]

The knock sensors will adjust for lower octane fuel. The knock sensors do not have infinite adjustment. When timing retarded to the max and there is still knocking or pinging you are damaging the engine. A low elevation hot situation is a good example of when 87 octane could damage your vehicle.

Phoenix is 1300 feet above sea level and crawling on I-10 the car sometimes will say 126-128 degrees. So I run 91/93 octane all the time. I also run NOS or NX octane boost at the track. These two brands octane boost can raise the octane value by 60 points bring 91 up to 97.

The G holds what 14-15 gallons when the fuel light comes on. Premuim is 20 cents more then regular so why risk your motor for $3 a week?

Telcom man has good advise on the IRA. I started my Roth IRA when I turned 19. $25 a month still compounds. Am 29 now and wife is 28. Over a grand a month is split between Roth IRA/ SEP IRA and 401k and we buy long term stocks on SCOTTTRADE.

Invest now retire early. I'm not planning on working after the last kid goes to college. We have 15 year mortgage and own property on San Pedro Island Belize. By 45 I should be living in Belize full time and teaching SCUBA!

Jeff

[USAF_G35_Guy]

NICE^^ SCUBA FTW!

So ya gonna be like the "instructor" on Along Came Polly? haha and hook up with the tourist chicks

[gwoods]

NICE^^ SCUBA FTW!

So ya gonna be like the "instructor" on Along Came Polly? haha and hook up with the tourist chicks

Exactly,

"luben are you for scuba?"

[DJM AutoWorks]

if you are leasing the car i would go with 87 but being that i own mine i go with 93 and we have 93 here in NY...im a nissan tech and i have heard pining in the 3.5 if the person doesnt use middle to high grade fuels....so i guess its your choice and how your vehicle feels and sounds...

[2mhighside]

I work in Saudi Arabia and all over the middle east. They still have leaded 95 octane over there and it would cost me about $6 US to fill my G. WTF!!

[Q45tech]

Many producing countries subsidize gasoline prices to placate population.............vs US which has a tiny 50 cent tax and EU where taxes may be $3-$4.93 to discourage consumption.

Venezuela subsidizes gasoline so much that it costs 7 cents per gallon at the pump. US consumers are paying the difference in higher oil prices same with all producing countries.