Hot weather mileage decrease

We too have noticed a drop in mpg from 50 to 45 when driving around town (Tucson) and running errands. When in and out of the car alot, the AC is constantly having to re-cool the cabin from 140-degrees to mid-70's.

My wife learned this week, that by turning the AC from "auto" to "two bars," the mpg shot back up near 50!

 

In Ballamer, so far this summer has been unseasonably hot and dry
with daily temps running in the mid to upper 90's with occasional
excursions above 100 degF. This is what we expect in mid to late
August... I don't even want to speculate what August is going to be like.

This follows a winter of record breaking snowfall... we all speculate if
there's a connection; neither global warming nor cooling, but much
larger seasonal temp swings.

I hate to use the airco, but this year I've relented and set it at 78 degF.

I'm seeing FE reductions of 5 -10 MPGs despite trying numerous hyper-
mileing tricks/tactics. The variation in MPG losses is due other driving
condition effects; traffic, etc.Amapola is a Gen II.

With a ScanGauge, which shows SOC in 1/2% steps, it is easy to see
the effect of the airco. Stopped, when the ICE isn't running, SOC can
drop 1%+ a minute. Yikes! With the OEM guaging, it's difficult to detect
the slow, minute-by-minute HV drain, resulting in more frequent ICE-on
to keep the HV battery in the HSD's operating preferences.

This ain't what the song was talking about:

 

2 bars , do you mean fan speed?

 

I have been running my A/C on 75 (f) since I bought it the 1st of May. I can not see any effect on the mpg since my numbers continue to go up. Maybe that is because I am getting more used to the car? The temps in Texas are in the mid to high 90s with a lot of humidity this summer. My HSI is showing a mpg of 58mpg on this tank of gas!

 

Yes. Two bars of fan speed.

 

Yeah but Brownwood has about as much city traffic as...say... Goldthwaite.

 

An update: Here in Tucson, it was 102 degrees yesterday. Yet, our mpg is now running 54.5. . . .up from the mid-40's a couple of weeks ago. The AC is set at 74-degrees and the fan at two-bars.

The only true variable is a fresh tank of gas.

There was an article in the local paper last week about the State busting a hand full of local stations for blending too much ethanol into their fuel. They were running 14% instead of 10%. I wonder if an untested station, one that we used, perhaps was running even more than that! That would explain the MPG discrepancy.

We are embarking on a 5000 - 6000 mile road trip next week (West Coast, BC and back), so it is good to see the numbers back up where we expect them.

 

My mileage has also decreased a mile or two since we started having 100 degree days here in central Arkansas. It's not a huge hit, but it is noticeable. I am guessing that the batteries aren't charging as efficiently.

 

I am in Dallas where it has been 100-106F for the last few weeks. I Just filled up yesterday and got my best mileage on an entire tank of 54.1mpg. I run the Ac at 77-79F but go down to 75/74F when my spouse is in the car (her call not mine).

 

I am going to give the AC tip a try. Do you think the humidity has anything to do with MPG in the summer? The actual temp here is about 95, but the heat index is about 110.

 

Humidity increases the air conditioning load. The latent heat of vaporization for water is 540 cal/ml, so every ml of water that driped out of your AC required 540 calories to condense.

Tom

 

This spring I regularly achieved MPG's in the 60's, summer sees 55 tops! Dead of winter I was glad to get 50 MPG! Perfectly happy with those numbers!

 

Here my results

 

Keep an eye out for gas pumps that indicate alcohol blends. It seems that Virginia stations all have a blend.

 

Who's the forum's archaeologist?

Just wanted to share, last week the temperatures here were between 100 and 105F (37 - 41C) and my mpg dropped A LOT!
My average gas mileage is around 45mpg (5.2 l/100) in the city when it's up to 86F (30C), but last week was very hot and the average mpg decreased to 34 (6.9l/100) and the car felt a lot weaker / under-powered. The ICE was running almost all the time, the SOC indicator wasn't moving almost at all (stayed at 2 or 3 bars at any time). At the first day I got scared a bit , but at night, when the temps dropped, everything was normal.

offtopic: F*** climate changes, the last years winter temps here drop to -13F (-25C), and at the summer they go up to 111F (44C)...

 

yea, it just keeps getting whackier.