I believe your mileage was still climbing because the engine monitoring was still ‘adjusting’ and optimizing timing etc for the higher octane fuel.....and it takes a while for it to make all the adjustments little by little. I’ve heard it could take as many as 3 tanks before it fully ‘optimized’ settings for the increased octane. That’s assuming you kept running the same fuel mix for several tanks consecutively.
Ethanol Free Gasoline
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I believe your mileage was still climbing because the engine monitoring was still ‘adjusting’ and optimizing timing etc for the higher octane fuel.....and it takes a while for it to make all the adjustments little by little. I’ve heard it could take as many as 3 tanks before it fully ‘optimized’ settings for the increased octane. That’s assuming you kept running the same fuel mix for several tanks consecutively.
swathdiver
Full Access Member
Yessir, I believe you are correct. Do you run ethanol in your Suburban?
hunterxx12
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Ever since refiners and blenders of gasoline ramped back on their use of MTBE since 2005ish, most moved over to ethanol because it was 1) a cheaper alternative to blending in or refining higher octane feedstocks to unleaded gasoline to meet higher octanes and 2) using oxygenates (MTBE and ethanol) in non-attainment areas in the US made it almost mandatory to use ethanol to not further exacerbate the low air quality standards in most heavily populated urban cities.
Ethanol does have lower energy density than pure gasoline on a like for like comparison hence why filling up your GM vehicle with E85 and driving under identical circumstances will yield less mpg than its lower ethanol cousin E10.
Vehicles now are intelligent enough to advance or retard timing based on all of the different blend ratios (i.e. you fill up with E85 and drive to almost empty and fill up with E10. You are now running <E85. You get back closer to home to your local E85 dealer and fill up with E85 and now you are somewhere in the middle). Your vehicle is adjusting back and forth with all of that extra oxygen meaning it potentially is never operating at maximum performance.
Ethanol also has a propensity to weaken certain soft metals in older carbureted engines (i.e. marine, yard, cycle, and other small engines) as well as attacks and drys out some gasket materials.
It's also hygroscopic which means it loves water. This means it's difficult to ship in nondedicated pipelines because it will pick up all of the water in the bottom of the pipeline as well as it acts as a solvent and it would potentially clean out the pipe. That sounds like a good thing in some ways but all of that gunk ends up somewhere and that can be at the bottom of your local service station's tank or at the bottom of yours. So ethanol is shipped via tank truck or barge and blended into a blend tank with gasoline then shipped to your local service station.
The posters that recommended using Sta-Bil are spot on. Gasoline should be used in approximately 30 days before it starts to gum and cause varnish. Because it has so many light ends, it will start to evaporate and leave that sticky varnish behind. Fuel technologists I have spoken to recommend using Sta-Bil with premium gasoline as a fuel of choice for small engines. The higher additive treat rate in premium tends to stabilize gasoline longer than lower octane unleaded gasoline.
Ethanol is a necessary evil and I can't imagine it disappearing anytime soon. But given the choice, I'd run pure gasoline every day of the week if I could.
Ethanol does have lower energy density than pure gasoline on a like for like comparison hence why filling up your GM vehicle with E85 and driving under identical circumstances will yield less mpg than its lower ethanol cousin E10.
Vehicles now are intelligent enough to advance or retard timing based on all of the different blend ratios (i.e. you fill up with E85 and drive to almost empty and fill up with E10. You are now running <E85. You get back closer to home to your local E85 dealer and fill up with E85 and now you are somewhere in the middle). Your vehicle is adjusting back and forth with all of that extra oxygen meaning it potentially is never operating at maximum performance.
Ethanol also has a propensity to weaken certain soft metals in older carbureted engines (i.e. marine, yard, cycle, and other small engines) as well as attacks and drys out some gasket materials.
It's also hygroscopic which means it loves water. This means it's difficult to ship in nondedicated pipelines because it will pick up all of the water in the bottom of the pipeline as well as it acts as a solvent and it would potentially clean out the pipe. That sounds like a good thing in some ways but all of that gunk ends up somewhere and that can be at the bottom of your local service station's tank or at the bottom of yours. So ethanol is shipped via tank truck or barge and blended into a blend tank with gasoline then shipped to your local service station.
The posters that recommended using Sta-Bil are spot on. Gasoline should be used in approximately 30 days before it starts to gum and cause varnish. Because it has so many light ends, it will start to evaporate and leave that sticky varnish behind. Fuel technologists I have spoken to recommend using Sta-Bil with premium gasoline as a fuel of choice for small engines. The higher additive treat rate in premium tends to stabilize gasoline longer than lower octane unleaded gasoline.
Ethanol is a necessary evil and I can't imagine it disappearing anytime soon. But given the choice, I'd run pure gasoline every day of the week if I could.
avalonandl
Full Access Member
Thank you for the long winded but accurate explanation that is on point.
Much better than the long winded & irrelevant replies one member with the initials b and g in their screename puts on this forum. Your new enuff so you may not have experienved this "wonderful" event...
wjburken
Supporting Member
hunterxx12
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Thanks for your response. Our ethanol situation here in the US is not a simple one so I did my best to summarize it for the average user.
I've been a "lurker" on this site for quite a while so I figured it was time I contribute back.
Tozan
Overlander
I don't think we have E-85 or E-15 stations anywhere in Reno.
avalonandl
Full Access Member
Whatever do you mean?
You mean WHOEVER do you mean
BLESS ITS HEART.........
If you add that its OK....
bigdog9191999
Full Access Member
although not as science as hunter used one aspect of e85 that can have very large benefit is in the aftermarket performance aspect. aggressive cam especially with increased compression and much more dramatically so under boost the cooling effect of the alcohol in e85 is dramatic and can have serious performance gains.
example would be if you say did a cam and an lsa blower, with headers intake, larger injectors ect your power increase over premium can be quite significant. dowfall is increased fuel usage as you will likely be using in the 30-50% more fuel , but cost vs premium and cost per hp usually make it a worthwhile venture if you have e85 accessible in your area.
there are some other effects depending on what year your vehicle is but when in the land of performance we tend to have some compromise to make.
me personally I run it in my supercharged 3800 powered car. a line of vehicle and engine that was never designed to be compatible with e85 with very little negative effects. our biggest issues are usual fuel system upgrades to get enough flow to supply the amount of fuel required to push as hard as we would like. I swapped one of my cars for cost savings ( some other modifications made my mileage absolute crap, so I swapped so at least the fuel was 1/3rd the price and saved a few bucks overall, and managed to get a little extra power also)
example would be if you say did a cam and an lsa blower, with headers intake, larger injectors ect your power increase over premium can be quite significant. dowfall is increased fuel usage as you will likely be using in the 30-50% more fuel , but cost vs premium and cost per hp usually make it a worthwhile venture if you have e85 accessible in your area.
there are some other effects depending on what year your vehicle is but when in the land of performance we tend to have some compromise to make.
me personally I run it in my supercharged 3800 powered car. a line of vehicle and engine that was never designed to be compatible with e85 with very little negative effects. our biggest issues are usual fuel system upgrades to get enough flow to supply the amount of fuel required to push as hard as we would like. I swapped one of my cars for cost savings ( some other modifications made my mileage absolute crap, so I swapped so at least the fuel was 1/3rd the price and saved a few bucks overall, and managed to get a little extra power also)
swathdiver
Full Access Member
My truck gets better MPGs on average on low levels of ethanol than on E10. I presume it's because she's making more horsepower per cylinder. I wish BlackBear did tuning for the ethanol tables, mine are stock.
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