E0 91 or E10 93

5933 Views 14 Replies 9 Participants Last post by GM Master Tech, Jun 19, 2014

McNeo

Discussion Starter · Mar 27, 2014

We've all read that ethanol-free gas is great. In my car with my own very basic "tests" (read: Fuelly) I've found I get better gas mileage with ethanol-free, though not enough to make it pay for itself.

I've also read we want to run premium in the summer for various reasons.

Long story short, I've got all the options around me. I could do all the "testing" I want but honestly I don't understand engines, why different octanes matter, why ethanol matters, all that crap. I mean, I get the basics, but you know...

With no tuning, no performance mods, and a lead foot - what's the all around best I can run?

E10 89, E10 91, E10 93 or E0 91?

Thanks

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spacedout

· #2 · Mar 27, 2014 (Edited)

If you look at the RPO code list in your glove box, it will list these two below. Sure the owners manual says the engine will run on 87 octane but doesn't say it wont run better with premium. Based on the RPO codes I would say the car was tested with 91E10.

KRD - FUEL RATING OCTANE NO. 91
FHO - VEHICLE FUEL GASOLINE E10

I have done quite a bit of octane/ethanol testing, my car runs the best with 90+ octane with ethanol. If I know I'm taking a long highway trip that's when i gain the most MPG with 91E0. 93E10 and 90E15 are good for 39mpg at 70mph in 50F weather, 91E0 42mpg.

Only fuel I like that's less than premium grade is the E15 available at my local ethanol plant(all 2012+ GM cars can run up to E15, see your owners manual). E15 is 88.5-90octane(depending on octane rating of the fuel the ethanol maker starts with), it cost 10-15cents less than regular 87 but preforms somewhere between midgrade and premium. I get the same MPG with E15 as I do with E10.

EDIT: I'm stock with no modifications to my cruze.

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spacedout

· #3 · Mar 27, 2014

Should also add always try to buy from a high volume station so you get fresh fuel. Most drivers only buy regular 87 octane though, so you still could get old crappy gas buying premium. At a minimum I would run 89E10, never any less.

McNeo

Discussion Starter · #4 · Mar 27, 2014

Thanks for the info.

From what I've seen the mileage is fairly similar which is what made me question. I've read that ethanol free can give you a little more bang and better throttle response - not sure if I actually feel that or if it's just mind over matter because people say it.

spacedout

· #5 · Mar 27, 2014 (Edited)

McNeo said:
From what I've seen the mileage is fairly similar which is what made me question. I've read that ethanol free can give you a little more bang and better throttle response - not sure if I actually feel that or if it's just mind over matter because people say it.

No ethanol gas will give you slightly better mpg, but not throttle response. Ethanol fuel will actually perform better in the cruze(better knock prevention for the turbo engine). My cruze runs its bet on 93E10, seems to rev a bit quicker in the higher RPM range & make more power.

Around where I live 93E10 is rare, most stations only offer 91E0 as premium. Stranger yet All BP, Shell, Mobil, & Cenex gas stations around here can carry either one, just depends on where you go. My local BP has 91E0, can drive 20 miles away and get BP 93E10.

Just remember at a minimum run 89E10 and you will have no problems, once above 80F outside run as high of octane as you can get. On those 100F+ days last year I could feel a difference in my cars performance with the AC on just topping off 1/4 tank of 93E10 on top of the 91E0 I was using. This summer I plan to try and run E15 and see how well it can handle the heat, hoping I can get away with not running premium that way.

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jblackburn

· #6 · Mar 27, 2014

I'll make it simple:

Best MPG - no ethanol.
Best performance - the Cruze loves ethanol, especially in the summer. It offers higher knock resistance that the engine benefits greatly from, especially in 90-100F weather with the AC running.

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PanJet

· #7 · Mar 27, 2014

Maybe you already understand this as part of the "basics" but I'll give you a quick, lay men's terms (that's what I am!) rundown in case not.

Octane actually inhibits ignition slightly. Higher octane means the fuel can resist burning under higher pressures and resist detonating.

Typically most turbocharged engines have required premium (high octane) fuel to prevent knocking and detonation because of the higher compression environment. While that is still the case, with active computer control of the engine parameters, engineers have at least partially overcome that by using knock sensors which can adjust ignition timing and such to compensate. Hence, the Cruze being a mainstream car can run just fine on regular fuel. However, it will run better on premium fuel because it will not have to compensate by adjusting timing.

As far as ethanol goes, ethanol does not have as high of energy density as regular dino juice, so that is where you should in theory see better fuel economy by using e-free fuel. Personally I haven't noticed any major difference with e10, but some folks have said they have seen mileage drops of a couple percent or more using e10. Back in 2004 when my parents first got a Tahoe with a FlexFuel engine capable of running e85, we ran a couple tanks of e85 just to try it out, and there was a very noticeable drop in mileage.

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spacedout

· #8 · Mar 27, 2014 (Edited)

PanJet said:
Back in 2004 when my parents first got a Tahoe with a FlexFuel engine capable of running e85, we ran a couple tanks of e85 just to try it out, and there was a very noticeable drop in mileage.

Sure is a huge drop going from E0-E10 to E85. I have driven that same style flex fuel tahoe and can say for a fact that up to E50 there was no significant loss in MPG. I had similar experience with the flex fuel Impalla loaner the dealer had me in(what, you didn't expect me to fill with regular gas on my dollar did you?).

To get E50 you used to have to fill at half tank, now all these new stations carrying E15 have blender pumps that offer E10, E15, E30, E50 and E85. Every 5% ethanol bumps the octane up 1 point, so if E50 fuel is made starting with the same low octane fuel as the E15 I run, your looking at 94 octane rating.

GeoHawk

· #9 · Mar 27, 2014

spacedout said:
If you look at the RPO code list in your glove box, it will list these two below. Sure the owners manual says the engine will run on 87 octane but doesn't say it wont run better with premium. Based on the RPO codes I would say the car was tested with 91E10.

KRD - FUEL RATING OCTANE NO. 91
FHO - VEHICLE FUEL GASOLINE E10

FWIW, my 2014 has the KRD RPO but I don't have FHO. I have FJW - VEHICLE FUEL GASOLINE instead (without the E10). I don't know if this means anything or not.

All the gas stations around me sell E10 for all octane grades. No one has pure gas.

Erastimus

· #10 · Mar 27, 2014 (Edited by Moderator)

Does E50 confuse the engine management system, if that system was specifically designed to manage only E0, E10 and E85 fuels? I ask because I seem to remember reading in a flex fuel vehicle owner's manual the instructions on how to switch over from E10 to E85, which if I remember correctly, instructs to run the fuel tank down as much as possible before switching.

CruzeEcoBlueTopaz

· #11 · Mar 27, 2014

Is there a map availble to the cruze for a 93 octane fuel ? Would it recognize an octane above 91 ?

jblackburn

· #12 · Mar 27, 2014 (Edited)

CruzeEcoBlueTopaz said:
Is there a map availble to the cruze for a 93 octane fuel ? Would it recognize an octane above 91 ?

The Cruze aggressively increases timing as far as possible, then backs off once it trips the knock sensors. The stock ECU tune allows quite a bit of wiggle room between fuel grades.

Will you benefit from running 93 over 91? It would depend on your driving style, area, weather, etc. Same goes for even 91/93 vs 89. With my current weather here, my car hasn't been tripping on the knock sensors even on 87. I'll have to jump to midgrade once it gets warmer again.

I notice the benefits of increased octane the most at < 1800 RPM, but it will pull/run a little stronger between 2000-3000 as well on 89/93 than 87.

I refuse to pay $5-7 more per tank unless it's absolutely necessary, though, especially if it doesn't show much of a MPG benefit (you'd have to test for yourself, but the difference for me is ~2 MPG). The price gaps between octane grades here are just ridiculous.

spacedout

· #13 · Jun 18, 2014 (Edited)

I didn't want to start a new topic when there are so many already on the subject. I decided to do some MPG testing with 91E0 vs 93E10. All fuel was bought at the same Mobil gas station & pump, weather was always around 75-85F. Average speed was 39mph with at least 30% city driving and mostly two lane highways and back roads.

http://www.cruzetalk.com/forum/members/219-spacedout-album698-stuff-picture81145-mobil-91-93.jpg

91 octane no ethanol: 1311 miles, 33.78 gallons / $4.10 a gallon = 38.8MPG
93 octane 10% ethanol: 1050 miles, 27.63 gallons / $3.99 a gallon = 38.0MPG

By the numbers there looks to only be a slight advantage to no ethanol fuel but I'm not sure this limited testing tells the whole story. On 80% or more highway drives I have never broke 40mpg with 10% ethanol fuel but have 14+ times with no ethanol. Even the testing above included a 41mpg fill up on no ethanol. Either way if it cost more money its probably not worth the cost to go no ethanol.

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iTz SADISTIK

· #14 · Jun 18, 2014

I'll have to try that out. Is there such a thing as 93/0??

Sent from iFail Mobile

GM Master Tech

· #15 · Jun 19, 2014

Vtuner told me tuned the 1.4T engine will make almost 20 more HP(flywheel) on 93 over 91

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