Cleaner tail pipes with 93 octane

Messages
386
Location
NYC
Hey everyone, I've recently switched to premium and noticed my car's exhaust tips aren't as black as they used to be with regular fuel. I think my turbo DI engine prefers higher octane rated fuel, my manual allows for 87 octane but using 93 offers around 10 more horsepower. Fuel economy seems to be improved slightly, my "miles to empty" meter has been increasing after each fill-up. Has anyone experienced similar results using premium fuel? I know some of these changes I'm seeing could be all in my head but Hyundai has released statements indicating the ECU can take advantage of premium fuel. -Thanks
 
Messages
16,016
Location
N.H, U.S.A.
Makes sense on the turbo - even my little fit gets black tailpipies when the ecu pulls timing and ramps up egr to deal with a tank of mysteriously very low octane fuel*. The fit does have over 10.5-1 compression and high cyl pressure at 4K+ rpm when the vtec kicks in. Octane rating can drop well below 87 if E10 phase separates due to water content above 0.3%.
 
Messages
10,008
Location
Upstate NY
Yep, my turbo Cruze sees noticeably better fuel economy and power running 93 octane over 87. It's cheaper per mile to put in premium than regular in that car. Our Fit doesn't seem to care one way or the other. It runs fine on 87 and not any differently on 93.
 
Messages
1,429
Location
quebec canada
Was gona say you likely baught gas without ethanol(cheer)but its unlikely .lot of state have unreasonably high limit .i hear shell v-power is ethanol free .if you did buy a gas without ethanol at 93. Octane ?there would be a huge difference . Lese then the brand top priced gas usually have ethanol .only top tier is usually without ethanol(at least in quebec.)they sell so little pmtop tier that it is almost irelevent value .so goverment worded law so its acceptable everybody happy everybody win. Gas as 114000 btu Ethanol has 74100 btu (about) As you can see it isnt helping on performance side,in low concentration tho you would want its benefit even if you loose a bit of power,but here is the rub ,most of the time you get too much of it.sweat spot is 1 or 2% of ethanol.so you likely baught low % ethanol gas.lucky you.south carolina isnt so lucky
 
Messages
17,238
Location
Upper Midwest
Why ouch? Octane is the same. You can have other issues with ethanol, but an octane rating is an octane rating.
Originally Posted By: yvon_la
Originally Posted By: Boomer
Shell V Power pumps here say "Up to 10% ethanol".
outch
 
Messages
2,806
Location
Michigan
can someone care to explain why power/mpg varies with 87 gas from different stations? in my diesel, I find the same, and when I researched it, it was attributed to the cetane rating of the diesel.
 
Messages
13,616
Location
Frisco, TX
Originally Posted By: stockrex
can someone care to explain why power/mpg varies with 87 gas from different stations? in my diesel, I find the same, and when I researched it, it was attributed to the cetane rating of the diesel.
I'm not sure I understand. You're implying not all gas is created equal? And that you've measured that?
 
Messages
669
Location
North Bend
Originally Posted By: stockrex
can someone care to explain why power/mpg varies with 87 gas from different stations?
Different additive packages in the gas. More or less ethanol content in the gas (there could be seasonal variations on this as well). Possibly issues with tank cleanliness or other maintenance at the individual station. In a given area, most gasoline arrives by pipeline, frequently from the same refinery. But it's possible that an area is served by multiple pipelines so it's possible to get fuel from more than one refinery.
 
Messages
5,108
Location
Columbus,Nebraska
I have used Sinclair 89 octane E-10 in my 04 Camry V6 since new ,and there is no carbon build in the exhaust tip or part of muffler which can be seen.The Sinclair station in our town recently closed and I have gone to the Shell truck stop for fuel. I decided to try the 91 octane without ethanol the last fill up and I can't detect any difference at all.
 

gathermewool

Site Donor
Messages
8,927
Location
New England
It makes no sense to use lower octane than recommended? I don't recall any owner's manual ever stating, "we recommend the use of 87 AKI and no higher, unless you really, really want that extra HP and MPG." I bet the engineers sigh in frustration when the marketing fellows tell them that they need the ECM to run most efficiently on premium, but to also not grenade itself if regular is used, so they can market this potentially (note, I did say potentially) false economic benefit to the "I want my cake and to eat it, too" crowd. Now, that's not to say that an engine with high compression or a forced induction can't be designed to run better and more efficiently than a similarly-spec'd lower-conpression or NA engine on regular octane fuel, but I'd bet that advertising the top MPG and HP numbers and that only regular fuel is required, all in the same breath, is more about marketing than practicality. Finally, if your engine is designed for 87,but can take advantage of higher octane, then increasing octane slightly (e.g., 89 or 91 AKI) makes more sense to me than going straight to 93. Heck, even engines designed to run premium and NOT ever regular octane have to account for the extremely low grade 91 AKI found in states like CA.
 
Messages
5,763
Location
Da Swamp
My Regal's manual, like that of a great many non-performance cars, says 87 or higher. However -- The code LAF 2.4L DI non-turbo engine in my car is supposed to have 11.4:1 compression. Would that be high enough that running a tank of 93 or even 89 might result in a little more power and drivability? Not necessarily gas mileage. I tried it in my Park Avenue with the NA 3.8 engine, and the mileage went down. But what about seat-of-the-pants drivability?
 
Messages
13,616
Location
Frisco, TX
Originally Posted By: Benzadmiral
My Regal's manual, like that of a great many non-performance cars, says 87 or higher. However -- The code LAF 2.4L DI non-turbo engine in my car is supposed to have 11.4:1 compression. Would that be high enough that running a tank of 93 or even 89 might result in a little more power and drivability? Not necessarily gas mileage. I tried it in my Park Avenue with the NA 3.8 engine, and the mileage went down. But what about seat-of-the-pants drivability?
Butt dyno is horribly unreliable. As I said, you need to look at fuel trims to know if it's helping, hurting, or doing nothing.
 
Messages
792
Location
Denmark
I am not into the octane numbers used in the US. But I can say for sure. That my own Mazda 1.8 mzr goes about 1 more km/litre if I fill it with our 99 octane. Instead of the 95 it requires. There is no difference to feel when driving.
 
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Messages
211
Location
Sta Catarina, Br
Ethanol is 105-110 octanes equivalent. It helps to raise the octane number of any gasoline it is added. The engine runs smoothiers for that. You guys should start to bust this huge amount of myth that ethanol isn't good for the engine.
 
Messages
5,435
Location
KC
My tailpipe on the Mazda3 has also gotten less black since I have owned it but I attributed it to startron. Maybe it is my exclusive use of premium that does it.
 
Messages
16,016
Location
N.H, U.S.A.
Originally Posted By: Rosetta
Ethanol is 105-110 octanes equivalent. It helps to raise the octane number of any gasoline it is added. The engine runs smoothiers for that. You guys should start to bust this huge amount of myth that ethanol isn't good for the engine.
When it gets wet -its garbage. And it doesn't take a lot of wet. Our gas IN So. NH. has never been this unreliable since E10.
 
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