Nautilus 2.0 2022 fuel economy with 93

[Ralph Greene]

My wife's 2022 Nautilus (22,000 miles 35 months old) gets better fuel economy on 93 VS 87. Not scientific, but she makes about the same 20-22 mile urban trip every day. To grocery stores, library, gym, etc. The dash MPG read out says usually in the 24.2 or so MPG on 93, and 22-23. or so on 87. This is not stop and go driving but does have traffic lights every 1-5 miles. Speed rarely exceeds 45 MPH. And it's been reading this way for past several months since I switched to 93.  And I know this is not a scientific test. And on a recent trip, saw over 30 MPG for whole tank. 34 once with a little tail wind. Now I know 93 octane fuel does not have more energy in it than 87. It has chemicals that reduce it's volatility so as not to knock and preignite. It just allows you to run more compression (direct injection allows this with a cooler charge) and timing. And our cars are tuned to pull timing on 87, and I can tell the slight difference in performance. Is it possible that when the CPU goes a while without detecting a knock, it goes back to a 93 octane tune. It still makes sense economy wise to use 87. 93 gives about 5% better fuel economy, and the fuel costs about 25% more around here. Mostly use Shell. And I doubt if carbon build up is any different on 93 VS 87. But I think 93 sure drives more "lively". For a 4200 LB vehicle, that little Turbo 2.0 has adequate power for a family passenger car. Anyone else notice this?

[akirby]

All ecoboost engines work that way.  They advance the timing (not compression) to take advantage of higher octane then back off if it starts knocking.

[twintornados]

Typically 93 octane fuels don't have ethanol mixed in which will also lower your MPG's.

[Flying68]

On 3/8/2025 at 8:51 PM, Ralph Greene said:

My wife's 2022 Nautilus (22,000 miles 35 months old) gets better fuel economy on 93 VS 87. Not scientific, but she makes about the same 20-22 mile urban trip every day. To grocery stores, library, gym, etc. The dash MPG read out says usually in the 24.2 or so MPG on 93, and 22-23. or so on 87. This is not stop and go driving but does have traffic lights every 1-5 miles. Speed rarely exceeds 45 MPH. And it's been reading this way for past several months since I switched to 93.  And I know this is not a scientific test. And on a recent trip, saw over 30 MPG for whole tank. 34 once with a little tail wind. Now I know 93 octane fuel does not have more energy in it than 87. It has chemicals that reduce it's volatility so as not to knock and preignite. It just allows you to run more compression (direct injection allows this with a cooler charge) and timing. And our cars are tuned to pull timing on 87, and I can tell the slight difference in performance. Is it possible that when the CPU goes a while without detecting a knock, it goes back to a 93 octane tune. It still makes sense economy wise to use 87. 93 gives about 5% better fuel economy, and the fuel costs about 25% more around here. Mostly use Shell. And I doubt if carbon build up is any different on 93 VS 87. But I think 93 sure drives more "lively". For a 4200 LB vehicle, that little Turbo 2.0 has adequate power for a family passenger car. Anyone else notice this?

It is actually quite simple, the higher octane produces more power across the power band.  So for a constant speed, your RPM is fixed when the torque converter is locked up, which you would think would require the same amount of fuel, but it doesn't.  If you are generating more power at that rpm, the computer will reduce the throttle and fuel to match the power output to the power required to maintain that rpm.  Thus you get better fuel economy.  I have seen it with my Expedition, going from 87 to 91 (93 isn't available here that isn't a blend of 30-40% ethanol). 

[akirby]

On 3/9/2025 at 7:29 AM, twintornados said:

Typically 93 octane fuels don't have ethanol mixed in which will also lower your MPG's.

Not in GA.  93 here is always E10.  Only a few stations sell E0.

[akirby]

3 minutes ago, Flying68 said:

It is actually quite simple, the higher octane produces more power across the power band.  So for a constant speed, your RPM is fixed when the torque converter is locked up, which you would think would require the same amount of fuel, but it doesn't.  If you are generating more power at that rpm, the computer will reduce the throttle and fuel to match the power output to the power required to maintain that rpm.  Thus you get better fuel economy.  I have seen it with my Expedition, going from 87 to 91 (93 isn't available here that isn't a blend of 30-40% ethanol). 

93 doesn’t have or produce more power.  It just allows the computer to advance the timing and that’s what produces more power.  With 87 you can’t advance the timing as much or you get predetonation (knock).

[92merc]

Here in ND, "most" premium is 91 octane and doesn't have ethanol.

 

I had a 2013 Escape with the 2.0EB.  I had done testing with 87 ethanol, 89 ethanol, and 91 no ethanol.  I did just one tank tests.  But I didn't notice any difference in mileage or perceived power.  There was maybe a 1mpg gain with premium.  Not even close to enough to justify the increase in cost.

 

I currently have a 2020 Escape with a 2.0.  This vehicle gets considerable better mileage.  I went from 22-23 tops on the old Escape, to 26 mph mixed, up to 34 mpg on the highway.  That's all been on 87 ethanol.  I'm so happy with that, I've never tried premium.

 

I also ride a BMW motorcycle.  That bike requires 89 octane minimum.  It will run on 87 in a pinch, but it'll retard the timing and reduce power.  Since I like to keep by the book, I've never put 87 octane in.  On that bike, I do get better mileage on premium.  Even when comparing w/ethanol to w/ethanol.  But in this situation, the increase in fuel range of about 20 miles a tank is important to me.  Especially on road trips where fuel ups are few in North Dakota.  So in that case, it's worth the premium to me.  Plus ND has dropped 89 octane.  It's now 87/ethanol, 87/non-ethanol, 91 octane.

[twintornados]

7 hours ago, akirby said:

Not in GA.  93 here is always E10.  Only a few stations sell E0.

 

In Central NY, most, if not all premium blends are ethanol free.

[akirby]

2 hours ago, twintornados said:

 

In Central NY, most, if not all premium blends are ethanol free.

Interesting.  In Ga we have 87, 91 and 93 E-10/15 and a few stations have a completely separate pump for E0.  Not sure of the octane rating.