Heatwave=low MPG?

The energy needed by the A/C is a function of the temperature difference. The hotter, the more energy needed. Although compared to ordinary cars, our A/C is very efficient, it isn't free.

I go more by humidity than temperature. For the most part, I try to run without A/C since I have dogs to walk and run.

Bob Wilson

 

my mpg dropped to ~35 mpg while driving on Monday from the east coast when the temperature was ~100F. i had the a/c full high for quite a while. i never have seen 30s except during the break-in period (first tank). for that tank, i got about 45 mpg eventually. what is really concerning is that today i had my first oil change, filled gas, drove for about 15 miles with a/c kept at mid-level, and the mpg is only about 35mpg on the HSI. i used to get 48-50 on the HSI with the a/c on but 30s are really concerning. any feedback would be appreciated.

 

Kinda interesting as you are seeing the same kind of hit that I take during the winter (0-20s) up here. The car is sensitive to these variations but it will all average out in the end.

 

Check the oil level on the dipstick!

 

oh!ok i have to do that tomorrow. i assumed the dealer will fill it properly. will a slightly low oil content affect mpg?

 

My mileage is down into the low 50's, temps were 101F this week. I Keep the AC at 75F but have been removing the re-circulate selection. I believe the recirculate will not pressurize the cabin enough to force cool air into the battery vent. Switching the cabin vent to flow from outside air creates a positive pressure in the cabin and therefore forces cool air into the battery vent.
Try it

 

I've had problems previously regarding the wrong oil used by dealers and there are a few threads on here about it. I only draw your attention to this as you have just had the car serviced and had an mpg hit.

If they have overfilled the oil then your performance and mpg's will suffer. If they have used the wrong oil (should be 0w20) then you will also have driveability and mpg and performance losses. At least those were my findings after the dealers allegedly put normal oil in my car at the 10k & 20k services.

The car returned to its normal mpg's and performance once 0w20 was put in and not overfilled. Also check your tyre pressures. I have found mine at 30psi after a visit to the dealers where they've obviously thought 37psi was too high, even though that is what it should be.

 

I checked the oil, and for the first time ever since I owned any car, i could not say for sure what the actual oil level is. On one side of the stick, upto the full mark the oil covered the entire width of the stick, and for an inch or so beyond the full level, there was some oil but not covering the entire width. On the other side of the stick, the oil was less than the full mark but not covering the entire width. I tried all ways to get an accurate reading but right now, but nothing worked. I am not sure whether the oil is more or less now! The service sheet says 5 quarts, and our manual says only 4.4 quarts is required.
Tire pressure is 37 on the front and 35 rear.

 

The stick is hard to read for sure. I had a Camry that was the same way.
Also check the service sheet to see what type of oil they put in. It it doesn't specify, call them and find out. It really needs to be 0W-20 as Grumpy indicated. If they used their 5W-20 bulk, tell them you want a redo!

 

the service sheet does say 0W-20

 

I would double check your oil again in the morning after the car has been stood on the level all night. If they've overfilled it, then that could be the cause of your problems.

After my last 20k service I immediately had driveability and mpg problems. The invoice indicated I had 0w20 oil but the car was much quieter and sounded smoother on cold starts, hesitated at engine startup, had reduced power - esp in power mode and had reduced mpgs. The same symptoms I had after the 10k service.

To cut a long and already reported story short, the dealers replaced the oil with 0w20 and didn't over fill it this time either. The car is now fine, mpgs back to normal, performance is great again. A way I found to easily tell the 0w20 oil is that the engine is much noisier on a cold start, even when the oil is new. The thicker stuff the dealers deny they used made the car sound much quieter at cold start.

Do you see any similarity between my experience and your own?

 

I chekced the oil after it was parked all night. But I'll check again tomorrow at work where the parking lot is more level. Grumpy, the cold start info is valuable information. i'll have to check when I start next time. Interestingly, my cold start has always been very quiet. Of course, here I am comparing the start to my 15 yr old corolla. Last week (before oil change) I noticed that the start became noisier if the ac was on, and quiet if the ac was off (more likely related to ac compressor).
anyway, i plan on driving for a couple of more days, and check for cold starts, and mpgs. if things do not improve, take it back to the dealer and ask to check the oil and level.

 

You can easily hear the sound of the AC compressor by simply turning the AC off and then on, preferably when the ICE isn't running.

 

That is the sound of wear.

 

not normal. I live in arizona. 105+ degrees every day. still averaging 50mpg.

and trust me, the a/c is on 24/7. usually when you reset the trip meter, the mpg will be low for awhile because the acceleration will drag it down but it will average out eventually.

 

I live in Texas and the A/C is an absolute necessity. My mileage has fallen off about 2 mpg since the really hot weather set in. My prior car (Volvo S70 T5) lost 3-5 mpg during the summer. Part of it is the additional drain due to the A/C; part is the reformulated gas they sell in the summer months on account of all the ozone.

Also, I do not have covered parking at work, so my car is really hot when I get in it to go home. The A/C works very, very hard, and the first part of my trip has a lot of traffic lights and stop and go traffic. The hybrid battery gets pretty well drained, so the engine ends up running a little more.

 

Indeed it probably is, but I'm using the correct oil as recommended by the manufacturer. If I use thicker oil I get significant performance, fuel economy and driveability reductions.

What am I to do.

 

I have read in threads here and on other forums that elevated HV
battery temps reduce the battery's ability to accept charge and provide
power.

This would mean additional ICE-on time and further FE/MPG reductions
beyond that from the ICE having to run to replace power drawn from
the HV battery to run the airco, especially when the ICE is off when
stopped or in one of the three ICE-off conditions of regen, no-arrows
glide, or EV operation.

Today I got a bit of a surprise. Full sun all day, temps in the mid/upper
90's degF. I opened the rear hatch to load some parcels and the cross
bar for the retractable hatch area tonneau (whatever!) was
excruciatingly hot to the touch. I mean really uncomfortably, drop-it-
right-now hot. So was the frame of a small folding hand truck lying on
the hatch floor. I can easily see how that amount of heat could work its
way through the hatch area rug and floor and to the HV battery.

I have an aluminized Heatshield hatch window sun screen but wasn't
using it! A clear case of operator error. Dumb, huh?

I've decided that from now on I'm going to extend the hatch area cover
thingy 24/7 and place the unrolled aluminized sun screen flat on the
cover, its not in the window at all, and can hardly be seen except when
standing next to the car.

My intention is to keep the hatch area from getting direct sun rays and
hopefully remaining cooler than it was today. I guess you could say
that the area under the cover now won't get any circulation. I can see
how there could be more heat in the passenger compartment.

Could my plan provide significant temp reduction at and below the
hatch floor?
Any foreseeable problems/issues?

 

I live in Texas where it is usually very hot in the summer. Lately, it has not only been hot, ie, high 90s but very humid. I recently made a trip to Abilene, a little over 160 miles round trip and my mileage actually went up! I was running A/C at 75 f the entire trip. I have been averaging 51.4mpg on the HSI and actually saw 58mpg during the trip!
Needless to say, I was incredibly happy with the trip. The mileage is holding even with my little trips around town.