Sudden decrease in fuel economy

[Laurel]

We have the SEL and life time mileage is 6.6 L per 100 kilometers.  But we have been getting great mileage of late with the weather warming up i.e. lots of 4.0 L and 4.4 L trips.  A bad trip is 5.8 L.  Today weather is 20 C so it is nice and warm and my mileage is just awful.  My same routes that would be 3.0 L downhill to home are now 9.8 L and going out uphill where I would have been 5.2 or so was 11 L per 100 kilometers.  Nothing different happening, driving the same way.  I am due for the first servicing this month--haven't booked it yet as I am waiting for the MFT upgrade to come out.  Hubby thinks the car seems to be reving higher than usual --that is to his ear.  Any ideas of what might be going on?  It is oh so discouraging.

[Bob999]

Are you using "top tier gasoline"?--basically fuels that use a high grade additive package to keep the fuel system and engine clean.  If not I would try a bottle of high grade fuel system cleaner.  Techron is a good brand and widely available--at least in the US.

[plus 3 golfer]

That is a big difference. Like Bob999 indicates it could be fuel related. You could have filled with a bad batch of fuel. You might consider throwing in 2 bottles of Techron (IMO, the best I've used and it works) in the gas tank.

 

Also, make sure you didn't shift into low accidentally and also that the hill assist is off. I have occasionally found myself dropping the gearshift into low (mimicking what I would due on my TDI to go into Sport mode) and forgetting about it for a mile.

 

You can set MY View to show rpm and watch rpm. When you run in EV mode, does the FE show like it did prior? US it would show 60+ mpg. Any gas smell after driving as you walk around the car? When coasting without braking, is it normal? After driving, feel wheels to see is any are hot indicating brakes dragging. I would think any other issues that would cause very poor FE, would throw a dignostic trouble code, check engine light, or message.

Edited May 5, 2013 by Plus 3 Golfer

[Jus-A-CMax]

Laurel, also I will add: check is your tire pressure, make sure its up to spec. Or like me and Matt, run it higher. Its the last thing most peope will do and they don't care unless they see a "tire" symbol on their dash...oh oh. Sorry to hear about it but I think its just a blip - probably bad fuel as +3 thinks.

[Ryan McEachern]

Laurel,

 

Hello neighbour!

 

We are also enjoying then good weather. We have also been getting 4.0-5.0 l/100 km once the plug in battery is depleted.

 

This sudden low mpg you are experiencing is not normal, and you should hunt down its cause ASAP.

 

Like others have said, check the tires, do this even if you don't have a gauge, for the tires to cause this dramatic decline you would notice a soft tire just by pushing on the side wall.

 

Check that there is nothing hung up under the car, there has been so much construction around here lately.

 

 

Like mentioned, put the rpm up on your my view screen and go for a spin, report your findings. Someone else will have some numbers to compare it to.

 

Actually, your downhill numbers are so high I wonder if you are even going into EV? Does your battery gauge discharge and charge normally, or does it seem really high all the time lately?

 

I'm tempted to come over to your side and take your car for a spin, my curiosity is certainly piqued.

 

Give us more data!! Lots of troubleshooters and problem solvers on here.

Edited May 5, 2013 by Ryan McEachern

[Laurel]

I recently filled up, but my mileage was good the two days after the fill up. Same gas station.  When I was driving today it was all in town driving, and most of the time I was in EV.  All the gauges seemed to look the same to me i.e. EV mode after getting up to speed and dropping back a little on the gas, no big white ICE consumption line (I'm not good at describing the technical stuff).  Hubby checked the tire pressure a couple of days ago.  I will make sure the downhill brake assist isn't on or the parking brake on a little.  Basically everything seemed as per usual on the gauges so I was shocked with the mileage when I turned the car off---four different trips with dreadful mileage.  No smell of gas.  Maybe bad gas is the answer and it took a couple of days to foul things up.  We will go for a drive after dinner and check the rpms.  Tip is due for the servicing but our mileage is just about 3200 kilometers which is very low over the past six months.  Oh dear, oh dear woe is me.  If the after dinner trip shows the rpms to be normal range and the mileage is still stinky, I will buy some Techron stuff and put it in.  Thanks everyone.

[Laurel]

Ryan with my downhill numbers I am often coasting and not in EV a lot.  I have thought that my battery seems not to charge as fully as usual.  I will check for a soft tire.  I think I will take it for a spin now and not wait until after dinner.  I'll let you know what happens.  I will do a route that has a fair bit of uphill going and downhill coming home.

[Laurel]

I don't have too much to report other than I was in too much of a friggin' hurry heading out. I don't really want to talk about it as I accidently reset the life time average and the dog got sick in the car.  I will re do my experiment tomorrow.  I cannot believe I did that reset!

[Laurel]

I am such a techno idiot.  I just went out to look at that life time reset.  So when I start the car it still shows 6.6 L at the bottom of the empower screen, but when I turn the car off now it says life time 4.1 L.  What have I done?  I am mixed up now as I never have seen that life time showing up when I turn off the car--I usually see mileage for the trip and my mpg for the trip.  I could slap myself for pushing buttons madly trying to find the rpms.  Now I am totally confused.

[salsaguy]

Make sure you NEVER fill up your gas when there is a gas tanker truck at the station filling up the tanks. It causes turbulence and gets all the junk/dirt/sediment on the bottom to come up into your gas fill up and then clog your fuel system.injectors thus getting bad mileage. you would have to then put cleaner in (or Techron gas as suggested) to fix it

[zhackwyatt]

I am such a techno idiot.  I just went out to look at that life time reset.  So when I start the car it still shows 6.6 L at the bottom of the empower screen, but when I turn the car off now it says life time 4.1 L.  What have I done?  I am mixed up now as I never have seen that life time showing up when I turn off the car--I usually see mileage for the trip and my mpg for the trip.  I could slap myself for pushing buttons madly trying to find the rpms.  Now I am totally confused.

The lifetime is reset separately from the MPG (or L/100KM?) that shows up in the Empower display.

 

When folks are referring to the lifetime they usually refer to the display that is shown when you power off the car.  It cycles between the trip and the lifetime everytime you power off the car and you can use the steering wheel controls to scroll between the two until the display goes off.

[Laurel]

So maybe I didn't really bugger up my life time average since it is still coming up 6.6 L.  I will be out on a few small trips today --plant shopping.  So I will report back later.  The only thing that I determined that was different yesterday that yielded the awful mileage was hubby had sneaked on the air conditioning which I had not noticed.  But that seems an huge spike as my mileage more than doubled on every trip ie. from 4.2 -5.4 normal runs to nearly 10 and 11 L runs.  I will try it with air conditioning and without and record the numbers today.

[Ryan McEachern]

Laurel,

 

The AC has a very minor impact on the mpg. You have so few miles on that car that I don't think you will get any value out of a fuel cleaner. I doubt you have bad fuel, although you may be running on an ethanol blend. Most of our gas up here is still 0% ethanol, but Husky and Mohawk both use ethanol blended gasoline. Was it a Husky or Mohawk you fueled up at this week? The type of fuel will not be causing this problem though, those 10 and 11 runs are way too high for that. When you say you don't go into EV downhill, do you mean that's because your foot is off the pedal? or is the engine idling even when coasting down I have to make a 40km run this afternoon, and I will do it in hybrid mode just to test some things out.

 

If you don't see an improvement today, maybe we should meet for a coffee somewhere and I could check out a few things. I am certainly curious what could cause average runs of over 10, that's about what this car would burn if it had a v6 squeezed under the hood and a regular powertrain.

 

You could use the info screens to make sure the climate control is not drawing an unnatural amount of power.

Edited May 5, 2013 by Ryan McEachern

[Laurel]

Ryan I am thinking it is the AC.  Today I took 3 trips out and about--most about 10-15K.  First two without AC, and one was back to the old 4.2L and the second had a bit of uphill and was 5.6.  Then I did a longer trip of about 20 K with AC on and it was 6.8L.  My temperature was set at 20C so I didn't have the AC really pumping cold air.  That 6.8L trip is on par with some of my cold weather trips.  No hellish results like yesterday. I think my husband had the temperature set at 18C yesterday with AC on when I got those awful mileage trips.  My fuel is from Safeway in Langley.  Yes my foot is off the pedal going downhill when I coast.  I did see improvement, but tomorrow we will head out onto to the freeway and go 60 or 70 kilometers with AC on and see what happens.  Thanks for your offer to test things.  I may take you up on that if things stay wonky.  The difference between the 5.6 L and 6.8 L run is translated to an 8 mile per gallon loss which seems  too much to me.

[Adair]

In light of the issues you are having Laurel, I paid attention to mine today. We drove into Ann Arbor (about 17 miles) for a race this morning and just had the recirc on. I was getting 43.8mpg. We drove home on the same highway this afternoon and needed the air. I noticed that if the battery was low to begin with, and the air on, even set at a moderate temperature, the battery would not gain any charge, even with the arrow pointing up. I turned the a/c off for a few miles, the battery charged, then turned the a/c back on. The battery stayed at a high level. The mpg for the return trip dropped to 42. I'm not sure what any of this means, since it's so early in the a/c season, but I'm sure gonna watch it. FWIW, both trips were on the freeway for 11 miles and city streets for about 6. While on the freeway I had ECO-cruise set to 65.

[StoBro2]

Hmmm, I usually have my heat set at 20C (68F) in the winter and my AC set at 25C (77F) in the summer. With the AC set at 20C or 18C (64F!) the compressor is sure to get a workout. I guess you like things cold up there in Canada!

[Ryan McEachern]

Laurel,

 

Good - those numbers seem more reasonable. We did a trip from Maple Ridge out go Coquitlam and back this afternoon, slow speed driving, nothing over 80km, had the AC set to 21, blower on 5 out of 7 bars. Outside temperature was between 29 and 32 degrees. I had air recirculation on most if the time, except the fresh air turns on automatically after each stop, so I forgot to turn it back to recirculation for a while.

 

35.6 km, 5.0Le/100km

 

I'll go do a test drive with the AC cranked to max just out of curiosity.

 

What an amazing hot spell recently and on the horizon, surely we are breaking records left, right, and center?

[Laurel]

Hmmm, I usually have my heat set at 20C (68F) in the winter and my AC set at 25C (77F) in the summer. With the AC set at 20C or 18C (64F!) the compressor is sure to get a workout. I guess you like things cold up there in Canada!

I think we do get used to cooler temperatures as heat waves are few and far between.  We were cooler today than Ryan who is inland and we are closer to the ocean, but it was about 26 C and that felt really hot to us--thus the 18-20 C air conditioning.  We long for the hot weather and first thing we crank on the AC.  People are funny eh?  At least Art Linkletter thought so.

[asb]

Laurel,

 

I recently posted the exact same issue.  It seems to have been the air conditioning.  I now run my air much higher (hotter) than I normally do.  That's helped a lot.

[Laurel]

Asb I guess I missed your post.  Sorry about that.  I will relax a little now.  I got used to cold weather affecting mileage and I could juggle things a bit to get better mileage.  Now it looks like I will have to juggle things with the AC.  That's okay as I still love my car.  I was panicking as I thought something was going haywire.  Thanks for your post.

[Ryan McEachern]

Laurel,

 

Just went for two quick trips to gather data. Exact same starting and stopping point. Route is along lougheed hwy for 7km, then up into the whonnock hills, and then back to the starting point on back roads.

 

Trip one, 15km, AC on low, blower on high 5.6Le/100

 

Trip two, 15km, no AC, no blower, all 4 windows cracked, 4.4Le/100

 

So it would appear that the AC can take away 20-25 percent of your fuel economy if the conditions call for it.

 

I noticed that having the AC maxed out really drives the numbers bad at slow speeds, not so noticeable at higher speeds, I guess because the energy used to cool the car is spread out over more km when driving fast, the penalty per km is less.

 

I took photos and will post then in a separate thread later.

[Laurel]

Wow Ryan even though I kind of thought my AC was really affecting my mileage,  it is shocking to see the difference in a somewhat scientific test that you did (my routes were not calculated like yours).  Thanks for taking your time to do that.  I really appreciate it.  I just read your post to my husband and is quite surprised with the results.  I guess we all we have to become very ecology minded in our cars.  We do that at home with turning lights out, setting the thermostat lower and wearing a sweater, and recycling our garbage.  Now we have to do that while driving too.  What do you think is this going to yield some stinky mileage from the folks living in places like Phoenix ?  I am surprised we are not hearing this from owners in the very hot climates.

[homestead]

Saw this in the C-Max manual on page 148 about Max A/C, this surprised me...

 

E. MAX A/C: Press to distribute maximum air conditioning through the instrument panel air vents.

This mode is more economical and efficient than normal air conditioning.

[salsaguy]

usually max ac is recirculated air not fresh outside hot air being cooled. it wouldnt thave to wok so hard to get  cool 

if u use max for a while to get the cabin close to desired temp then use normal ac at low you should get better mpg but yes in hot hot places ac will kill mpgs

 

 

Saw this in the C-Max manual on page 148 about Max A/C, this surprised me...

 

E. MAX A/C: Press to distribute maximum air conditioning through the instrument panel air vents.

This mode is more economical and efficient than normal air conditioning.

Edited May 6, 2013 by salsaguy

[plus 3 golfer]

Next time when one uses AC, set up MY VIEW to monitor the Climate and Other kW loads.  Set AC to AUTO.  You will see that the Climate load can be over 3 kW when the climate system is initially turned on especially if the interior is hot.  The blower will probably be running at a very high speed and the OTHER load will likely be about 1 kW.  After driving a few minutes, the Climate load should drop as the cabin air becomes cooler.  The Other load will also drop as the fan speed decreases.  When a balance point temperature is reached, the Climate will likely drop to between 1/2 - 1 kW.  Of course, the temperature that the climate system is set at and ambient temperature will affect the time and level of kW load to maintain the set point. 

 

If we could record the Climate and Other load and get the total kWh used at the end of a trip, we could then convert that load to BTUs.  For the Hybrid, all those BTUs come from the gas burned to run the engine (which likely has a thermal efficiency of only around 35-38% or so).  I ran a few tests last week and estimated that the average Climate load was about 0.7 kW which would equate to about a 7% reduction in FE.  This was very close to the actual reduction I saw from the same trip without AC.  However, had the compressor continued to operate at say about 2 kW level instead of about 0.7 on average, the FE decrease would have been around 20%.

 

As I've said in several other threads, the % fuel economy reduction due to using the AC will be significant in the C-Max because the base FE number is high in the C-Max.  It's fuel efficient and burns less fuel than an inefficient vehicle. So, using a small amount of fuel for AC is a significant % of the total fuel consumed in the C-Max relative to an inefficient vehicle.