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This is funny what you are saying to me))) gas grade does play a role with almost every engine - and this is a fact! put bad gas in and put good gas in and test - then talk here. Theories do not always work in practice! You can Prove if you can by sharing the link for the study or smth. But I was sharing my personal experience, unlike you, basing it on whatever and I saw that premium gas gave me 40+ miles more than regular. Believe it or not, I don't care, but this is a fact for me! FYI my car is brand new 1500 miles on it only and my mileage went from 13.4 to 19mpg as of yesterday. Also, I did the reprogramming thing yesterday also, but it is not for this thread.
Some folks on this forum have talked with Subaru engineers, who note that there is no performance difference between 87 and higher octane gas with the Ascent, because the Ascent hasn't been programmed to take advantage of it. There's also another thread on this forum from the folks at Cobb tuning. They are creating a new tuning profile for the engine, and they noted that the factory default tuning profile will not take advantage of any difference with higher octane fuel.

If your car has only 1500 miles on it, it may still be breaking in and that can account for a difference. Try switching back to 87 octane and see if you can reproduce the results. Be aware of factors like temperature, weather/wind, driving style, traffic, elevation, etc. could play a part in differences as well.
 

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I used Exxon, Shell, and BP for regular, all results came with pretty much the same mileage per tank, the premium was from BP as far as I remember and from the engine start it showed me 28-29 mpg, but then dropped to 22-23 on my way home, and then to steady 19-20. So apparently it doesn't work the way "best Subaru tuning company" claims it to be. But I will certainly be checking again.
 

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Sorry, @Maga233 but Subaru and COBB have both confirmed it. Multiple times.
 

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I used Exxon, Shell, and BP for regular, all results came with pretty much the same mileage per tank, the premium was from BP as far as I remember and from the engine start it showed me 28-29 mpg, but then dropped to 22-23 on my way home, and then to steady 19-20. So apparently it doesn't work the way "best Subaru tuning company" claims it to be. But I will certainly be checking again.
LOL
I’ll take COBB Tuning’s word over yours all day there buddy. You’re a little late to the party on this.

Been there, done that.
 

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I will add that early indicators in my vehicle point to a slight improvement in MPG with the stage 1 Cobb Tune on 93 octane when driven similarly. My Ascent lifetime fuel economy is 20mpg. Starting to creep over up now... food for thought.
 

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I will add that early indicators in my vehicle point to a slight improvement in MPG with the stage 1 Cobb Tune on 93 octane when driven similarly. My Ascent lifetime fuel economy is 20mpg. Starting to creep over up now... food for thought.
Yes, the COBB tunes remap things in ways that seem to be helping people with gas mileage. I am pretty sure that it's throttle remapping that's doing that, from watching the boost response to pedal pressure and comparing. Not very scientific, but it's what I've seen.
 

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I used Exxon, Shell, and BP for regular, all results came with pretty much the same mileage per tank, the premium was from BP as far as I remember and from the engine start it showed me 28-29 mpg, but then dropped to 22-23 on my way home, and then to steady 19-20. So apparently it doesn't work the way "best Subaru tuning company" claims it to be. But I will certainly be checking again.
I've done this a few times with my Outback ie switching octanes to test it out myself. My observation is that the octane switch confuses the ECU and the 'automatic' fuel consumption calculations are way off from actual. My calculated mpg remains unchanged. I choose to run 93 for the cleaner burn and additives.

My a/t tires and roof rack on the other hand... each one of those hit the mpg at least 2mpg. Ouch.
 

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Yes, the COBB tunes remap things in ways that seem to be helping people with gas mileage. I am pretty sure that it's throttle remapping that's doing that, from watching the boost response to pedal pressure and comparing. Not very scientific, but it's what I've seen.
I agree. Those are my observations as well
 

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LOL
I’ll take COBB Tuning’s word over yours all day there buddy. You’re a little late to the party on this.

Been there, done that.
I don't care whos word you take pal, I really don't. It was my experience, I see it with my eyes, not COBB's or yours and I will keep to that, really don't care about theories and official info these days, but only what I see, I am too old to believe in all statistics and go with somebody else's word. Period. And I am not late anywhere, as Long as I am here it is relevant to me.
 

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I agree. Those are my observations as well
Robert, I respect your opinion and like the videos you post, but I see this myself unless my ascent's computer is messed up and gives me wrong mileage info. full tank on regular 260-270, on premium 310, this is fact to me. All other info to me is very subjective as was obtained somewhere else bu someone else. I still dont like this mpg I get. 310 mls from 19gallon tank.
 

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I don't care whos word you take pal, I really don't. It was my experience, I see it with my eyes, not COBB's or yours and I will keep to that, really don't care about theories and official info these days, but only what I see, I am too old to believe in all statistics and go with somebody else's word. Period. And I am not late anywhere, as Long as I am here it is relevant to me.
Sorry you feel that way. COBB didn't make theories. This isn't statistics. COBB wrote the new ECU maps that a number of us are running on, after analyzing the stock ECU maps. Subaru hasn't made dual fuel/octane maps in forever.

It's literally fact.

I think it's placebo effect, or you got bad gas. But, what it definitely isn't is the 93 octane. You're welcome to believe whatever you want. Alas, we have over 6,000 members, who I'll refute it for with facts. Totally nothing personal.
 

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I've done this a few times with my Outback ie switching octanes to test it out myself. My observation is that the octane switch confuses the ECU and the 'automatic' fuel consumption calculations are way off from actual. My calculated mpg remains unchanged. I choose to run 93 for the cleaner burn and additives.

My a/t tires and roof rack on the other hand... each one of those hit the mpg at least 2mpg. Ouch.
yours is 3.6 or 2.4t? year? what is your mpg now?
 

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Sorry you feel that way. COBB didn't make theories. This isn't statistics. COBB wrote the new ECU maps that a number of us are running on, after analyzing the stock ECU maps. Subaru hasn't made dual fuel/octane maps in forever.

It's literally fact.

I think it's placebo effect, or you got bad gas. But, what it definitely isn't is the 93 octane. You're welcome to believe whatever you want. Alas, we have over 6,000 members, who I'll refute it for with facts. Totally nothing personal.
I am not saying it was about octane number, it is only the fuel grade i was talking about. Don't be sorry)) we are here to share opinions right? my opinion so far is the one I shared, maybe it will change, but for now, it is a fact for me. I am a first time Subaru owner and learning now, but I see the numbers on the dash and if it is giving me a wrong info then it is a different problem.
 

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yours is 3.6 or 2.4t? year? what is your mpg now?
2014 outback 2.5 NA MANUAL TRANSMISSION. I used to average 28mpg mixed use. Last year added a/t and roof rack down to 23-24. Historically I used 87 octane. The first time I used 93 it immediately registered it back at 28mpg!! Until a second tank it took until the calculations were more accurate. Ive tried it a few times. Oddly enough no matter which direction I switch it registers an “improvement” in mpg.
 

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I am not saying it was about octane number, it is only the fuel grade i was talking about. Don't be sorry)) we are here to share opinions right? my opinion so far is the one I shared, maybe it will change, but for now, it is a fact for me. I am a first time Subaru owner and learning now, but I see the numbers on the dash and if it is giving me a wrong info then it is a different problem.
Something we didn't explain (apologies) is that the Subaru ECU is a learning ECU. While ours only has an 87 map stock, it does always adjust for octane/fuel grade to ensure no knock. It also adjusts to the driver. When the fuel grade/octane changes, it takes a while to re-learn, during which time, numbers will be off.

The best way to test is to run 4 tanks in a row of each, and compare the final tanks by doing the math yourself. Eg: mark your mileage when you put in the fourth tank, run it to near empty, fill it up and mark the mileage again, and do the math yourself based on how much gas you put in.
 

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Something we didn't explain (apologies) is that the Subaru ECU is a learning ECU. While ours only has an 87 map stock, it does always adjust for octane/fuel grade to ensure no knock. It also adjusts to the driver. When the fuel grade/octane changes, it takes a while to re-learn, during which time, numbers will be off.

The best way to test is to run 4 tanks in a row of each, and compare the final tanks by doing the math yourself. Eg: mark your mileage when you put in the fourth tank, run it to near empty, fill it up and mark the mileage again, and do the math yourself based on how much gas you put in.
Now we are talking, I will try. And yes I know ECU is the one that learns from the way I drive and hoping to teach this sucker to save gas))
 

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Now we are talking, I will try. And yes I know ECU is the one that learns from the way I drive and hoping to teach this sucker to save gas))
LOL, I decided that using the turbo at every opportunity was more fun. I hope you have better luck than me, and don't give into the temptation. ?

Seriously though, I've gotten it to the point I can get 22-23 mpg average combined. Maybe 21 on really bad weeks.

With my roof rack and spare tire roof mounted, I get 19-20 mpg combined. I'm too lazy to take off the off roading all terrain spare when I'm just commuting. ??

Anyways at over 51,000 miles on my Ascent, my gas mileage is whatever I decide. I suspect that you will get to that point too.
 

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LOL, I decided that using the turbo at every opportunity was more fun. I hope you have better luck than me, and don't give into the temptation. ?

Seriously though, I've gotten it to the point I can get 22-23 mpg average combined. Maybe 21 on really bad weeks.

With my roof rack and spare tire roof mounted, I get 19-20 mpg combined. I'm too lazy to take off the off roading all terrain spare when I'm just commuting. ??

Anyways at over 51,000 miles on my Ascent, my gas mileage is whatever I decide. I suspect that you will get to that point too.
The only heavy thing I have in my car is my ass)) I am a big guy, 6.2, 225lbs, gained a bit now, but that is pretty much it. Maybe I need to start with myself first and then complain)) Anyways I don't care anymore, bc I realize it is a big heavy car and it is normal mpg for this vehicle.
 

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I don't care whos word you take pal, I really don't. It was my experience, I see it with my eyes, not COBB's or yours and I will keep to that, really don't care about theories and official info these days, but only what I see, I am too old to believe in all statistics and go with somebody else's word. Period. And I am not late anywhere, as Long as I am here it is relevant to me.
Getting mad isn't going to change reality "Pal." :LOL:
Again, I don't trust a single word you say over COBB's, who's been working with Subaru ECUs for 15+ years. So good luck with your bad gas or whatever you're convinced you're experiencing. You haven't even got enough miles on or experience with the car to attempt to find anything of significance or consistency.
 

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Ok, c'mon, let's not let the thread go more down hill.
 
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