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Discussion Starter · #1 ·
With COVID finally winding down I've been able to do a few more longer trips in my 2020 WRX...and I'm really disappointed in the fuel economy compared to the 2012 Outback 3.6R that I've been driving since it was new.

Background: I'm a bit rural so the standard driving is get up to speed fast and then set cruise around 60mph (55-60mph speed limits) and stay in between the lines for 30-60 minutes before you have to do anything. I've done enough drives I even worked out that my 3.6R Outback 6-cyl peakes around 62-63MPH speeds I would hit 28MPG with ease, even when I had it packed to the brim borderline overloaded with stuff. When I did the math on "gallons pumped to miles driven" the computer was a bit optimistic on that car, saying ~29MPG when my math said ~27-28MPG. After some recent service (PCV valve, transmission flush, wheel bearing), its still getting nearly that economy 10 years and 161K miles later and barely notices even a modest hill on cruise control.

My 2020 WRX Premium with its little 2.0L 4cyl (all stock) on the other hand, with 10K miles on it (thanks to COVID been not driving much since I got it new) I'm lucky if it will show 27-28MPG on the display and my gallons-pumped to miles-driven puts it more like 24-26MPG at the same ~60MPH cruise speeds and same roads, and even the slightest hill it seems to struggle and ends up hitting ~5psi boost trying to hold 60mph, more if its a medium hill (we're not talking mountains here, just like maybe 1/10 or so mile up/down say 50-100ft or so elevation change maximum).

I get that these aren't intended to be record-breaking efficiency cars, but I really expected to at least meet the highway economy ratings...with the exception of a rental Jeep in literal mountains that didn't have enough torque to climb at interstate speeds, every vehicle I've driven (Ford, Mercury, Hyundai, Subaru, Mazda, Nissan) I've easily beat the EPA rated highway mileage by a couple MPG by simply getting up to speed, set cruise control, and don't make any sudden movements or speed changes.

I keep the tires about 3PSI over the "recommended", they've got good tread on them (as I say, this car is basically new at 10K miles), clean, running the recommended premium/93 fuel, upshifting at the speeds recommended in the owner's manual (so at 60mph its in 6th gear), foot stays totally off and away from the clutch pedal once moving so no chance I can see how it'd be letting it slip (I'll admit, this is also my first stick-shift).

I hear people say "don't boost if you want mileage" but how is it possible to maintain speed and accomplish that? I don't think setting cruise between 60-65 should be too crazy a speed to need to be asking anything crazy is it?

Is there something I'm missing?
 

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There are countless factors that come into play and we have had numerous people exceeding 30mpg highway and nearing 30 average on the fa20f.

Either way, you are well within the vehicles EPA rating as those ratings are ideal conditions and temperatures.
 

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Discussion Starter · #4 ·
There are countless factors that come into play and we have had numerous people exceeding 30mpg highway and nearing 30 average on the fa20f.

Either way, you are well within the vehicles EPA rating as those ratings are ideal conditions and temperatures.
The ratings I see put them at 21 city / 27 highway for the 6-speed WRX 2.0L (non-STI) vs the 24-26 highway - 1-3 MPG lower than rated highway?

I feel like it ought to be better given the much bigger Outback with a 3.6L engine is only rated 18 city / 24 highway and I easily get 27-28 highway without even trying - 3-4MPG more than rated highway?


I've seen others hitting 30 highway on these cars and I'm trying to figure out what's different, why mine doesn't seem to, and how to do better.
 

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As for your boost limitation, my CVT has 3 modes on it, the « i » mode is the « softer » one and barely make any boost at low throttle. I think it’s controlled by the boost solenoid and other factors.

I don’t know if you got that mode options to switch from to help your boost levels.


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Discussion Starter · #6 ·
As for your boost limitation, my CVT has 3 modes on it, the « i » mode is the « softer » one and barely make any boost at low throttle. I think it’s controlled by the boost solenoid and other factors.

I don’t know if you got that mode options to switch from to help your boost levels.


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I'm not aware of any such control with the 6-speed transmission model I have, unless there's something I'm not finding in the manual.
 

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The ratings I see put them at 21 city / 27 highway for the 6-speed WRX 2.0L (non-STI) vs the 24-26 highway - 1-3 MPG lower than rated highway?

I feel like it ought to be better given the much bigger Outback with a 3.6L engine is only rated 18 city / 24 highway and I easily get 27-28 highway without even trying - 3-4MPG more than rated highway?


I've seen others hitting 30 highway on these cars and I'm trying to figure out what's different, why mine doesn't seem to, and how to do better.
No. It shouldn't.

Many factors including but not limited to altitude, temperature, humidity, road surface, tires, the lower out of boost torque of a low displacement turbo motor, oil viscosity, gearbox oil viscosity, the age of the fluids.

You are doing fine. Many people never see 20mpg.
 

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Not sure what you r complaining about, I get 16-18. I can get 28-30 if I want to but it takes some effort. Put boost n throttle position on triple gauge, keep rpm at 3k-3.5k, throttle under 20% n boost under -4psi. 60mph is 4th or 5th depending on slope. Gentle throttle inputs, sharp press for even 2mm pedal travel will spike throttle position to 90%.
 

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Discussion Starter · #9 · (Edited)
Not sure what you r complaining about, I get 16-18. I can get 28-30 if I want to but it takes some effort. Put boost n throttle position on triple gauge, keep rpm at 3k-3.5k, throttle under 20% n boost under -4psi. 60mph is 4th or 5th depending on slope. Gentle throttle inputs, sharp press for even 2mm pedal travel will spike throttle position to 90%.
Should that be reading any throttle % when its on cruise? Mine just sits at 0% the whole time its running on cruise even though the boost gauge varies from about -11 to +4 (what I observed today).

The throttle % bar only indicated anything as I was getting up to speed before I turned on cruise control. I can try and get a video later tonight if I can find a way to put a tripod to see the dash from the back seat while driving.

4th seems really low for 60mph its really screaming high RPMs (not hurting anything, but seems silly to be at like 3.5-4K when its cruising)...I was going by the suggestions in the owner's manual (since this is my first stick shift car) 4th to 5th at ~45mph, 5th to 6th at ~50mph. I'm going to give it a try in 5th but will have to wait for a weekend when I'm not in heavy traffic to evaluate highway mileage with any hope of being efficient.
 

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Don't forget that on anything drive by wire accelerator pedal and throttle opening are related but not always 1:1. So you may have the pedal at 30% but you are probably closer to 70% open throttle.

It drives me mad when I go from my Jeep that is 1:1 or my WRX at 1:1 to my Forester that's like 10:90.

Lower rpm doesn't always mean lower fuel consumption either. If you have to go hard in a specific gear to maintain speed, you don't need as much throttle and therefore less fuel at a lower gear where there is better leverage. You've got to play with it to find a sweet spot for your car. My Jeep for instance gets better fuel mileage at 55 in 4th gear than 55 in 5th gear because it's an anemic turd and you've got to stand on it in 5th to maintain speed.
 

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Lower rpm doesn't always mean lower fuel consumption either. If you have to go hard in a specific gear to maintain speed, you don't need as much throttle and therefore less fuel at a lower gear where there is better leverage.
This. There's a bar graph under the digital speedo that shows fuel consumption with red or green blocks. Watch it in different gears at the same speed with minimum throttle to maintain speed. 6th at 60 you will be half red with 50% throttle. 4th will be green with 10% throttle. This engine just runs better at higher revs. Below 2.5k, it bogs and runs with high EGT, high boost and quick heat soak (at least here, 104F yesterday).

Gauge probably doesn't read in cruise. +4 is dangerously high for maintaining speed. User manuals have given those same speed-gears for every car since ww2. If you see anything over -2 in cruise downshift. In general stay at 3.5k-6k for hard acceleration, 2.5k to 4k for moderate acceleration and around 3k for cruising. & slip the clutch at 4k to chirp the tires ;)
 

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Discussion Starter · #12 ·
This. There's a bar graph under the digital speedo that shows fuel consumption with red or green blocks. Watch it in different gears at the same speed with minimum throttle to maintain speed. 6th at 60 you will be half red with 50% throttle. 4th will be green with 10% throttle. This engine just runs better at higher revs. Below 2.5k, it bogs and runs with high EGT, high boost and quick heat soak (at least here, 104F yesterday).

Gauge probably doesn't read in cruise. +4 is dangerously high for maintaining speed. User manuals have given those same speed-gears for every car since ww2. If you see anything over -2 in cruise downshift. In general stay at 3.5k-6k for hard acceleration, 2.5k to 4k for moderate acceleration and around 3k for cruising. & slip the clutch at 4k to chirp the tires ;)
as I understand the green/yellow gauge on the digital speedo readout is +/- compared to average trip MPG (and it "resets" with the trip odo, which I reset on every refuel) so after a point you can't really get any higher than the center of the graph. I know there's a bar-graph available in the MFD for instant-economy but it doesn't have the resolution for precise comparisons, it goes in increments of 20.

Maybe I can look if Torque or OBDLink and see if I can find a proper numerical readout that will make comparison easier...I know my other car could report fuel-flow in gal/hr, I've not had much reason to put it on my WRX since it already has more readouts for temperature, cruise-set, and other useful parameters.
 

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as I understand the green/yellow gauge on the digital speedo readout is +/- compared to average trip MPG (and it "resets" with the trip odo, which I reset on every refuel) so after a point you can't really get any higher than the center of the graph. I know there's a bar-graph available in the MFD for instant-economy but it doesn't have the resolution for precise comparisons, it goes in increments of 20.

Maybe I can look if Torque or OBDLink and see if I can find a proper numerical readout that will make comparison easier...I know my other car could report fuel-flow in gal/hr, I've not had much reason to put it on my WRX since it already has more readouts for temperature, cruise-set, and other useful parameters.
Could be. Haven't reset the trip meter in months and the gauge still goes green all the time.

MFD graph is good enuf for constant speed. You will see a significant difference between gears. For exact numbers, track your fill-ups.
 

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Watched the economy gauge on a road trip. Best results at steady speed:

4th: 45 to 60 (flat), 50-70(uphill)
5th: 60-75 (flat), 70-90 (uphill)
6th - 75-90 (flat)
downhill: neutral to accelerate then engine braking to hold speed.
 
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