Need direction: sudden drop in gas mileage

[DoubleDee]

So in a drive today, my gas mileage is much lower than normal . Just a little at “full speed”, but way low, like single digits during acceleration. Feels a little sluggish, just not “normal”. Power meter definitely higher than normal during non electric mode, but switching to electric as usual. Not sure if this is something simple or if I should plan on a service visit?
2023 hybrid, 49k

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[Clarkdonbran]

 

[Chops]

So in a drive today, my gas mileage is much lower than normal . Just a little at “full speed”, but way low, like single digits during acceleration. Feels a little sluggish, just not “normal”. Power meter definitely higher than normal during non electric mode, but switching to electric as usual. Not sure if this is something simple or if I should plan on a service visit?
2023 hybrid, 49k

Air filters slowly get dusty - and dust actually attracts dust making it more effective. But eventually and quickly gets too dusty to be effective. A “hockey stick” function.

Anyway, a clogged air filter can hurt mpg’s.
Maybe check your filter? Probably not the reason but a quick & easy thing to eliminate as a possible cause. Good luck!

 

[scharris99]

Bad gas at the last fill up seems possible. As mentioned, when did you last change your air filter? Have you pulled the spark plugs to see what they look like? If you don't run top tier gas, when was the last time you ran some Techron through the engine to clean the injectors? When was the last time you accelerated hard for 10 seconds or more to give it ye olde Italian tune-up?

 

[allc0re]

Some folks are reporting reduced gas mileage due to the increased amount of ethanol now allowed by the regime to try and ease gas prices. My understanding is that E15 (instead of only E10) is now allowed to be used. Could be a factor. I've noticed my mileage has gone down a bit myself despite the weather not significantly changing.

 

[mwelby]

Some folks are reporting reduced gas mileage due to the increased amount of ethanol now allowed by the regime to try and ease gas prices. My understanding is that E15 (instead of only E10) is now allowed to be used. Could be a factor. I've noticed my mileage has gone down a bit myself despite the weather not significantly changing.

Yep, if octane says 88 don’t use it because it’s E 15. Bad stuff.

 

[mwelby]

So in a drive today, my gas mileage is much lower than normal . Just a little at “full speed”, but way low, like single digits during acceleration. Feels a little sluggish, just not “normal”. Power meter definitely higher than normal during non electric mode, but switching to electric as usual. Not sure if this is something simple or if I should plan on a service visit?
2023 hybrid, 49k

Did you tank up with top-tier fuel, or the cheap stuff? The cheap stuff will definitely affect fuel mileage.

 

[tiktokbrainrot]

Some folks are reporting reduced gas mileage due to the increased amount of ethanol now allowed by the regime to try and ease gas prices. My understanding is that E15 (instead of only E10) is now allowed to be used. Could be a factor. I've noticed my mileage has gone down a bit myself despite the weather not significantly changing.

E15 is not used for normal 87 octane gas. It's used for 88 octane. So unless OP bought the wrong gas, that's not the cause.

What everyone was losing their minds over was Trump approving a switch of blends early, because the summer blend uses more ethanol then the winter blend does, to try and offset the Iran situation. But the amount of ethanol in the summer blend didnt change.

If OP didnt see those changes last year, then the early change didnt cause this.

So in a drive today, my gas mileage is much lower than normal . Just a little at “full speed”, but way low, like single digits during acceleration. Feels a little sluggish, just not “normal”. Power meter definitely higher than normal during non electric mode, but switching to electric as usual. Not sure if this is something simple or if I should plan on a service visit?
2023 hybrid, 49k

First thing is to see if this behavior continues past the next fillup. Could have been bad gas, or because it was hot out, or for a myriad of reasons.

If it continues past the next fillup at a different station, then you have something more actionable to work with. Also, hand check you MPGs at fillups. The onboard indicator is unreliable, to say the least, and is more of an estimation based on a variety of factors.

 

[Matso]

I don't particularly trust the digital fuel economy gauge although I think it can be adjusted in Forscan but that's another thread. The most accurate method IMO is to fill up to one click at the pump. Drive until at least 1/4 or less in the tank. Fill up again at the same pump to one click and do your calculation. Simple, empirical and easily repeatable. Just not exactly convenient. Repeat that after any significant maintenance procedures such as filter change, tire pressure changes etc. If all other factors remain relatively constant you get an apples to apples comparison.

 

[UpACurb]

According to the forums your battery is dying

Dont feel bad - my Ecoboost just hit 500 miles so my transmission should be breaking any second now.......

 

[RetAcct24]

I suggest calculating your mileage and resetting the trip counter on every tank of gas to catch problems early.

 

[Maverick123]

Dunno if I'm imagining this but since the last (trailer module) OTA update, it seems like the ICE is running a lot more than usual.

Normally in summer I can drive out of my neighborhood without the engine starting, but the past few days I'm not even making it one block before it starts and there's a lot of situations where the engine wasn't running before but it is now. Also it feels harder to keep it in electric on a level road

 

[DoubleDee]

According to the forums your battery is dying

Dont feel bad - my Ecoboost just hit 500 miles so my transmission should be breaking any second now.......

It has had gas since starting, and still is happening. I’m not doing anything differently than I always have.

are you referring to the hybrid battery as opposed to normal battery, which I have already replaced recently?

 

[HeyBales]

Wow - can't believe the number of people that believe a change from "up to" (which likely means was) 10% ethanol to 15% ethanol would be meaningful in any short term manner.

Around here at least - permanent labels are normally "up to 10%" for the 87 Oct.

Did this math for another group saying it was the reason for a loss of 10 mpg.

1 liter ethanol has 21 MJ of energy, compared to 32 MJ for gasoline.
33% less energy per volume.
Who runs pure ethanol in their vehicle?! No one.

Pretend the old standard up to 10% was 10% ethanol then.
30.9 MJ for the mix - 3.4% less efficient than pure gasoline.
Ok - increase that mix up to now 15%.
30.7 MJ for the mix - 4.1% less than pure gas.
But only 0.65% worse than 10% was.

Ok - pretend in a gas guzzling truck - 15 mpg in prior 10% mix.
Now - 14.9 mpg on the 15% mix. oh yikes. (30 mpg would be 29.81)

$4.30 for 10% vs $4.05 for 15% price difference - say 300 miles then fillup.
$86 vs $81.54.
Only if the price remained the same would the efficiency matter - by dimes.

 

[HeyBales]

So in a drive today, my gas mileage is much lower than normal . Just a little at “full speed”, but way low, like single digits during acceleration. Feels a little sluggish, just not “normal”. Power meter definitely higher than normal during non electric mode, but switching to electric as usual. Not sure if this is something simple or if I should plan on a service visit?
2023 hybrid, 49k

So you are watching the instantaneous MPG figure it sounds like.
That actually has very good accuracy - system is using how much grams of fuel is being used to the estimated tire rotation distance - both pretty specific figures.

But any variation in wind, or air temp, or humidity - will show the difference there.
Meaning about impossible for you to match all variables for a meaningful repair.

Even over the exact same route, say an incline at a set speed exactly.
But it doesn't take much difference in Go pedal position to not change the speed but really change the MPG.

And the power meter.
That's a little better, as it's translating the torque values being handed out to horsepower for display.

So if you are up by a notable 5-10% to obtain the same cruising speed up an incline, or what feels like the same acceleration rate ("feels" is tough) - engine would be producing more for the same outcome.

Been using top tier fuel?
Even there though - mistakes can happen in what was delivered and you pumped.
Any correlation to this starting and any other events?

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