Hot weather killing fuel economy?

[dishdude]

I've never witnessed this before in the summer, but ever since the latest heatwave I've lost a ton of MPGs with this Integra. I used to average 30-31, now I'm at 23-25 which is ridiculous for this tiny car. I realize the air is less dense, but I've never noticed this in other vehicles in the summer.

 

[MParr]

Wow! I’m averaging 1mpg better than you and I’m driving an F-150.
How much ethanol is in your fuel?

 

[JHZR2]

Idling? Around town?

hot weather will make the ac run more continuous, which can add many hp load between the compressor, internal and external fans, etc.

It will take its toll, but that seems excessive…

 

[Warstud]

You should be getting better Mileage in this heat . Check your Brakes

 

[carviewsonic]

The a/c has been on and blasting to cool the black interior with every drive in our Accord for the past 3 weeks. Haven’t checked mpg, but it has to make a significant difference to fuel economy with a smaller engine like the K 2.4.
But your mpg drop does seem excessive.

 

[dishdude]

Idling? Around town?

hot weather will make the ac run more continuous, which can add many hp load between the compressor, internal and external fans, etc.

It will take its toll, but that seems excessive…

No change in driving habits, it's making the same trips it usually does. Yes, A/C is blasting and fans are roaring. No change in vehicle performance other than the drop in fuel economy.

 

[samven]

I have not seen as big a drop as you have but I have noticed a drop from 40 mpg to 37 because of the AC and the thin air. Even without the AC on I notice I need to down shift on hills that I could normally make in a higher gear. 1.6l Ford Fiesta.

 

[Oillover]

What octane are you running?

 

[miden851]

your latest gasoline quality, maybe use of different gasoline station perhaps or different fuel octane?

 

[dishdude]

What octane are you running?

It's been on a steady stream of 91 from Costco since new.

 

[SC Maintenance]

Here in the SouthEast - maybe not as hot as Phoenix but pretty hot, if anything I get the same or better MPG in the heat - all my vehicles, at least when I am driving. Idling for a long time in the heat will kill your MPG pretty quick though.

 

[DemoFly]

At 60 degrees the meter on the dash of my car says A/C is using 1/16th of a gallon/h to run the AC.

At 90 degrees (~65% humidity) with the fan on high it uses 1/2 a gallon/h.

While driving and at idle. Duty cycle on the compressor is basically the same. It just runs the e-fan at idle.

 

[miden851]

I've never witnessed this before in the summer, but ever since the latest heatwave I've lost a ton of MPGs with this Integra. I used to average 30-31, now I'm at 23-25 which is ridiculous for this tiny car. I realize the air is less dense, but I've never noticed this in other vehicles in the summer.

I think you're reading it incorrectly, also you're were clearly idling at the moment of taking this photo

that 23.5mpg is just the reading of your latest run, not necessary tied the full tank reading per say, neither the reading of trip A nor the trip B as a whole

 

[dishdude]

I think you're reading it incorrectly, also you're were clearly idling at the moment of taking this photo

that 23.5mpg is just the reading of your latest run, not necessary tied the full tank reading per say, neither the reading of trip A nor the trip B as a whole

I wasn't going to take a picture while driving, this was after pulling into the garage before shutting it down after a drive. The last tank averaged 24, this is since the reset 32.7 miles ago.

 

[JavierH19]

Heat increases efficiency. But with heat comes AC usage and the AC will cycle much more frequently. This is even more prevalent in auto stop start vehicles since they'll only stop once the interior has cooled down but if i forget to press the SS button it'll take a half hour for the truck to make me realize i didn't turn it off at stops. But in the winter it'll shut off by the second stop.

 

[SubieRubyRoo]

I wasn't going to take a picture while driving, this was after pulling into the garage before shutting it down after a drive. The last tank averaged 24, this is since the reset 32.7 miles ago.

With less than 2700 total miles, how can you can you accurately say you “used to average XXX miles” like there’s some valid history for this? That’s literally less than 6 full tanks of gas for the entire life of the car??

 

[miden851]

nah, I would not jump to the conclusion just yet, all things considered are the same

I'd fill it full again, reset the trip points, run the car and test it 'till the tank is empty

that's what I would do

edit; my Accord has the same points, and behaves more of the same

 

[dishdude]

With less than 2700 total miles, how can you can you accurately say you “used to average XXX miles” like there’s some valid history for this? That’s literally less than 6 full tanks of gas for the entire life of the car?

Do you really think I've only put gas in this car 6 times? Give me a break. The last fill up I was less than 200 miles into the tank and it was already at 1/4 tank.

 

[SubieRubyRoo]

Do you really think I've only put gas in this car 6 times? Give me a break.

That’s not what I said, is it? Nope.

Besides, the air being less dense actually helps fuel mileage apart from any other influences. To maintain stoichiometric, less oxygen in the air means less fuel injected into the engine.

Give it a few tanks, it will come back.

 

[MParr]

Here in the SouthEast - maybe not as hot as Phoenix but pretty hot, if anything I get the same or better MPG in the heat - all my vehicles, at least when I am driving. Idling for a long time in the heat will kill your MPG pretty quick though.

Here, it’s been hovering near 100F with 45% humidity.