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I have worked with product mangers on the technical side of things at Mazda, Honda and Toyota / Lexus and discussed this topic with them. In general modern engines use feed-back loops to self-tune adjusting for temperature, altitude, fuel grade, engine temp and other variables. One dynamic is ignition timing and any old hot-roder knows about tuning for the most advance you could safely run or re-curving distributors for even better effect. It is of particular note that modern engines have one or more knock sensors in the head which supports dynamically tuning ignition timing even at the cylinder level just as O2 sensors allow for dynamically tuning mixture. Premium car brands routinely specify premium fuel as it lets them make minor ECU changes and now we have more power but ignition timing auto advance is part of the secret sauce. Thus, the premium fuel helps create a result of more torque which makes the transmission work better etc (a big issue with Lexus drivability testing for example). All that said the difference with premium fuel alone is not that great but it is part of the way an Acura has more power with the same engine than an Accord. Honda likely makes 4-6 changes including premium fuel, higher flow air filters were one common change, a better muffler, and ECU changes; all things Honda has previously done in Honda vs Acura products.

Personal opinion - My 2.0t touring feels slightly better with Premium. On long trips I tend to use premium and anecdotally I seem to get a 1-2 mpg better mileage. My butt drives me out of the seat before the tank is empty and the extra cost is not recovered by 20 extra miles on a tank, still sometimes I select premium as a personal choice.
 

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Discussion Starter · #42 ·
I have worked with product mangers on the technical side of things at Mazda, Honda and Toyota / Lexus and discussed this topic with them. In general modern engines use feed-back loops to self-tune adjusting for temperature, altitude, fuel grade, engine temp and other variables. One dynamic is ignition timing and any old hot-roder knows about tuning for the most advance you could safely run or re-curving distributors for even better effect. It is of particular note that modern engines have one or more knock sensors in the head which supports dynamically tuning ignition timing even at the cylinder level just as O2 sensors allow for dynamically tuning mixture. Premium car brands routinely specify premium fuel as it lets them make minor ECU changes and now we have more power but ignition timing auto advance is part of the secret sauce. Thus, the premium fuel helps create a result of more torque which makes the transmission work better etc (a big issue with Lexus drivability testing for example). All that said the difference with premium fuel alone is not that great but it is part of the way an Acura has more power with the same engine than an Accord. Honda likely makes 4-6 changes including premium fuel, higher flow air filters were one common change, a better muffler, and ECU changes; all things Honda has previously done in Honda vs Acura products.

Personal opinion - My 2.0t touring feels slightly better with Premium. On long trips I tend to use premium and anecdotally I seem to get a 1-2 mpg better mileage. My butt drives me out of the seat before the tank is empty and the extra cost is not recovered by 20 extra miles on a tank, still sometimes I select premium as a personal choice.
Good write up and I am an old school guy. I built Big block fords and changed spark advance by buying different springs at the auto parts store :) How did we adjust fuel mixture? Change jets and run wide open then put it in neutral and shut the car off and read the plugs :)
 

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First off I want to say I am NO WAY saying run it or it will run better.
I have a 2021 Sport1.5 with around 1400 mile and has pretty consistently got around 24 mpg ( I watch because it was rated at 27 but I do a lot of 10 mile trips ).
But after reading a few folks here saying they runs premium fuel I decided why not, after all I am filling my car up about every 2 or 3 weeks.

Well to my surprise it starting averaging 26 MPG the next day after that fill up. Yea I know its not science and no where near the price difference but thought that was interesting considering I drive on the conservative side 95% of the time.

Car drive the same to me but curious if anybody else have notice anything similar??

I will show my age, I won't get into how much gas was but it was 10 cents between grade. 87 $1.20 89 $1.30 93 $1.40 as an example. Not sure why they started this price gouging.
Late to the discussion, but 1400 miles is not enough baseline history. Mileage is affected by a lot of things, including the weather, wind direction, whether you got whoopie this weekend, etc. I recently got really great mileage over a couple weeks because I worked 17 days straight: so nice slow drive to work with a quicker cruise home (where the beer is). But that's a good test, but not real world. Great mileage. (Warm/hot weather too which is always good for mileage).

You're quite correct that premium price will overwhelm the savings.

There are usually more additives as well in the higher grades, so better "value" for spending more than you need to.
 

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Discussion Starter · #44 ·
Late to the discussion, but 1400 miles is not enough baseline history. Mileage is affected by a lot of things, including the weather, wind direction, whether you got whoopie this weekend, etc. I recently got really great mileage over a couple weeks because I worked 17 days straight: so nice slow drive to work with a quicker cruise home (where the beer is). But that's a good test, but not real world. Great mileage. (Warm/hot weather too which is always good for mileage).

You're quite correct that premium price will overwhelm the savings.

There are usually more additives as well in the higher grades, so better "value" for spending more than you need to.
If I ever burn this tank full I will see 😀. My trips and weather are probably scared predictable during covad. Short trips getting lunch or groceries.
What I am really curious on is a hwy trip running 80 since that’s probably pushing the motor more. But heck no it’s not work the price difference just testing
 

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Summer of 2018, long road trip, speed 75MPH most of the time on the Interstates. I went over 900 km on one tank with a couple litres to spare. If I ever have to do a long work sched again, I'll drive slowly in both directions. Per the data (and I collect oodles) I can probably get over 1100 km on one tank with margin (in summer weather). (1.5L engine).[1]

A "benefit" at a speed like 80 MPH is the turbo waste gate is partially closed, so the exhaust is helping to pump air to the engine reducing pumping losses. The "boost" at this speed is almost equal to atmospheric. (Absent turbo it would usually be lower than atmospheric as the throttle would not be wide open).

[1] Sipping gas - I coulda been a contenda!
 
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Discussion Starter · #46 ·
Summer of 2018, long road trip, speed 75MPH most of the time on the Interstates. I went over 900 km on one tank with a couple litres to spare. If I ever have to do a long work sched again, I'll drive slowly in both directions. Per the data (and I collect oodles) I can probably get over 1100 km on one tank with margin (in summer weather). (1.5L engine).[1]

A "benefit" at a speed like 80 MPH is the turbo waste gate is partially closed, so the exhaust is helping to pump air to the engine reducing pumping losses. The "boost" at this speed is almost equal to atmospheric. (Absent turbo it would usually be lower than atmospheric as the throttle would not be wide open).

[1] Sipping gas - I coulda been a contenda!
Good info, my 2013 seemed to get better mileage at 80 then 65 :) luckily never had to try and explain that to a police man
My road trips are on open hwy and man lately people fly, too fast for me. Bad when your doing 83 and can’t ride in the left lane because your holding up cars
 

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Ask your self why gas stations sell reg for maybe 10 cents a gallon more then a sams or Costco but premium is usually 40 cents higher. I think gas stations jack the price up to take advantage of the folks that think they need it and probably don’t even check pricing :)
All good I won’t burn premium for an extra 1 mpg just posting what I noticed
Investors Business Daily used to post the wholesale prices of regular and premium gas in the commodities prices section. Back in the 90’s, there was less than a 5 cent difference between the 2. No idea what it is now, but I doubt it is more than a dime.
 
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Investors Business Daily used to post the wholesale prices of regular and premium gas in the commodities prices section. Back in the 90’s, there was less than a 5 cent difference between the 2. No idea what it is now, but I doubt it is more than a dime.
Theres a huge price difference range from $0.50 to >$1.00 at some places.

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Discussion Starter · #50 ·
Theres a huge price difference range from $0.50 to >$1.00 at some places.

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You will be surprised at how much is tax, I wondered why gas was cheaper at the beach in SC then in GA until I looked it up. Man it was an eye opener
 

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Great video and that’s about what I was seeing in my 1.5. Before some pull out weapons and start throwing things NO it’s not worth the difference from a dollar stand point.
The ONLY reason I run 93 is because of my tune. If not, I would run 87.
 
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I just filled 17.822 gals of Costco's 93 octane this afternoon. My MDX and the J35 turned into a different animal. Definitely the type of fuel you use determines how playful the vehicle gets. Typically I use 87 since I commute alot.

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I posted my true fuel mileage over a year ago and someone disagreed. I know this is a forum.
Let me word this in a question. Among many other things, ignition timing has what effect on fuel mileage? What is the real purpose of "knock sensors"? See the picture?
It's all about tuning/timing AND not melting the aluminum pistons.
98% of the time I run 87 octane, ethanol free. Now getting 35.3 MPG. Last fill up was 10% ethanol 93 octane. 36.1 MPG. Same 33 mile route, between 45 and 65 mph.
I hate ethanol.
Where I live, (So flo) ethanol free gas costs more than premium.
To add to that, I would also confidently say that ethanol free fuel would render better results in HP and MPG's than 87 premium fuel would.
 

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Well about a month or so later, I have a few more tanks of 93 recorded. most are 87, 93 are circled green. 24 tanks of 87 from 2/13/2021 to 8/27/2021 show an average of 36.29mpg. 5 tanks of 93 scattered in throughout that range show an average of 36.33mpg. Essentially zero difference at 0.04mpg, but now that I'm actually going to alternate every 2 tanks, I'll be able to get more numbers. I'll probably try to keep this up until thanksgiving. I am only on person and I obviously know which fuel is in the tank, but my motivation is to get the best I possibly can because to me, the lifetime average is the most important thing.
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Discussion Starter · #57 ·
I thought it was interesting he said the econ button didn't do much, I always thought that.
 

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If you're going to do a ton of highway driving, you're gonna regret using 93 unless your vehicle literally calls for it as a required fuel. 93 is not for the J35 at all even it has a tune for it. I feel like 87 gives the best range and MPGs when only comparing between 87 and 93. Instantenous reading max was 35.1 mpg on 87, 34.0 mpg on 93. Max range on 87 (my MDX was challenging me) is 640 miles, on 93 its 571 miles.

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I think he has the K20C4.
I just did the experiment with the J35. I'm pretty sure the K20C4 doesn't have a tune for 93 from factory, but I could be wrong. Even if that block has a tune for it, its not worth using 93 at all, because the only gain you will see is a 5 to 7 horsepower increase which isn't noticble at all. And also, just for highway driving 93 isn't worth it even for the K20C4 block. Maybe if your vehicle has the K20C1 (the CTR Engine) then yes, it needs 93 octane.

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