Noob Fuel Question!

Sibze

"""Originally Posted by Sibze
Is it not true that you would want to use 91 for pure performance though??? """""


By this I mean just fin use 91

Hugoneus

I did do a search, but I couldn't find something immediately. Thank you for posting the link.

kannibul

Fixed

Sibze

lol ok thats what I was trying to say...


Whatever...


USE 91 PEOPLE

kannibul

Use 91. The whole car *is* pure performance. There are no exceptions with the car stock or with bolt-ons.

The only exceptions would be an ECU tune (when they finally crack it well enough to advance the timing further), or forced-induction.

End of topic!

Sibze

On this topic that we have moved to…

In Canada the highest octane that we can get is 93 at Sunoco. They have a points program and give you a butt load more points if you fill up with 93.

Downsides of using 93?

kannibul

Cost. There aren't any gains to be had with using 93 over 91, short of an ECU tune or Force Induction.

That said, sometimes gas stations get batches that are under or over rated.

There are stickers on the pumps here in the US (not sure in Canada) that show a test date, and a +/- rating on 87 and 91 octane fuels. I've seen some test 87 octane as high as +5 (meaning it's 92 octane that day, that month), and as low as -2. 91, I'm just now paying attention do since the Z. I've seen a few say +2, others 0. Here, the gas is tested annually, so...they could go cheap and put crap gas in the tanks after their testing. Depends on the owner...the bigger corporate-owned places tend to be better (also go to the busy stations, they cycle fuels faster!), but the one-off ma-n-pa no-brand / small chain gas stations are the worst about it. They tend to get whatever gas they can get the cheapest when they need it most.

They don't test 89 octane here because it's really just 91 and 87 mixed in the pump.

Lastly, if you see the fuel truck at a gas station, don't get gas there that day. Sure it's the "freshest" and least likely to have any collected moisture in the fuel, but, all that fuel dumping into their storage tanks, stirs up sediment and out the pumps it goes into your tank, into your filter. Wait a day...

Sibze

Thanks!

I will have to work out the points difference and see if its worth it... however I am going to go out on a limb and say it wont be worth it...

Xan

Kannibul basically has everything covered.

The only things I can add is, on top of fuel not always being exactly as posted, hot outside temperatures could also induce knock and have your ecu retard timing.
Although the inlet air temp map will most likely be retarding the timing to prevent this, higher octane fuel could help here to reduce that effect.

Also certain types of molecules that mid and regular fuels contain do not exist in premium fuel, therefore premium fuels leave less deposits.

Finally as all major companies have their own additives to prevent build up, but in their process build up themselves, it can't hurt to switch brands every 3000 miles or so.
(although some companies buy their additives from others, so it won't work then)
The principle behind this is that one brands additive will remove the other and switching prevents maximum build up.
(I don't have any prove of this, maybe someone else has seen research on this? But it makes sense to my and it can't hurt)

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kannibul

No. 93 would not burn cleaner. It would burn less efficiently. However, with the variance in fuels being delivered to a given gas station it would give you more "wiggle room" before it would trip off the knock sensor, which would be even less efficient.

With 93 octane, you could be wasting a minute percentage of unburned fuel out your exhaust. For the most part, I would say negligable, but, you're referring to what percentage of the fuel is "octane" vs "heptane" - 91 octane is 91% octane, 9% heptane. 87 octane is 13% heptane, 87% octane.

Over 100%, it's based on some other method, and they use something otherthan octane to get it there, obviously, since you have have 101% (or higher) octane.

kannibul

Generally isn't. They must be having a hard time selling 93 octane to offer some kind of kickback system...but like a casino, the house always wins...

(former gas station manager)

kannibul

Right, I wasn't accounting for air temperatures and effects of cold air intakes and so on.

The part on less fuel deposits with premium fuels (in general), I don't believe that is true. I do know that different companies put in different additives, however those additives are done at the distribution station...the company requesting the fuel can request their "special recipe" and it gets mixed as the truck is getting filled up. That being said, it's about the same (generalization!) as putting in BRAND X fuel injector cleaner with a tank full of gas, vs a can of BRAND Y fuel injector cleaner. The levels of additives are in the extreme less than 0.01%. Not like with engine oil....

Also, if anything you'll end up with more carbon deposits if you use premium fuel in a non-premium-required-vehicle.

Xan

For non premium required vehicles that's true if you get a incomplete burn.

However if it does burn, premium fuels burn cleaner then non premium.

I don't know the Nissan ECU (but will be putting some time into this in the future), but for Jaguar's ECU's the advance timing map went well above the minimum octane spec in advancing timing under heavy load and has build in algorithms that take care of the ignition learning. So assuming that Nissan (or who makes their ECU's) do a similar thing, it actually would make a difference to use higher octane fuels.

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IDZRVIT

There are gas stations in Toronto and Montreal that now have 94 octane.

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"America.... still builds rockets!"
Vette: 355 cid, 400 rwhp
'13 CTS-V Coupe: 6.2L LSA, 556HP

kannibul

AFAIK, there are no ECU's that will advance timing (further) to compensate for higher octane fuels than required.