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Hey all,

I have a 2015 CT200h FSport that has about 43K miles on it. I bought it back in November used and I was getting great fuel economy in eco mode, averaging 44 with a mix of city and highway driving. In early January I loaded my car up with lots of stuff and drove about 100 miles that day with all those items in my car. Since then, I've had decreasing fuel economy. Right after that trip, I noticed my average was barely 37mpg, with similar driving to what I was doing before. The next week, I was down to 35, the next 33.

As of now I am still averaging about 34. I also notice a lack of overall power and the electric motor seems to be hardly used anymore. I notice that the car switches to full gas power at much lower speeds regardless of how I accelerate. I've been monitoring my battery levels throughout all this and they look perfectly normal, never dipping below 3/4 full.

In the past few days I've been driving in sport mode, and the car has been using the electric motor much more now, actually inproving my economy to about 35mpg. Not sure what this really means but I'm going to continue this for now.

I've read online that something like a dirty oxygen sensor, dirty fuel injectors, or bad spark plugs can be the cause. I'm going for an oil change this week as well just to rule that out. My tires are still good and are properly inflated, and I don't have a stuck brake caliper.

This huge drop in mpg is very odd to me and I was wondering if there is something I'm missing that would cause all this. Particularly the large drop in the electric motor's usage in eco mode. Anyone have any ideas?
 

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Cold weather & heater use results in the engine running more often. I'm in the same boat and figured it's just the weather.
 

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Cold weather & heater use results in the engine running more often. I'm in the same boat and figured it's just the weather.
I live in Florida, and I've used the heat maybe 5 times total. Plus the drop of started long before I ever turned on the heater. And would that really cause a 10mpg difference?
 

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Hey all,

I have a 2015 CT200h FSport that has about 43K miles on it. I bought it back in November used and I was getting great fuel economy in eco mode, averaging 44 with a mix of city and highway driving. In early January I loaded my car up with lots of stuff and drove about 100 miles that day with all those items in my car. Since then, I've had decreasing fuel economy. Right after that trip, I noticed my average was barely 37mpg, with similar driving to what I was doing before. The next week, I was down to 35, the next 33.

As of now I am still averaging about 34. I also notice a lack of overall power and the electric motor seems to be hardly used anymore. I notice that the car switches to full gas power at much lower speeds regardless of how I accelerate. I've been monitoring my battery levels throughout all this and they look perfectly normal, never dipping below 3/4 full.

In the past few days I've been driving in sport mode, and the car has been using the electric motor much more now, actually inproving my economy to about 35mpg. Not sure what this really means but I'm going to continue this for now.

I've read online that something like a dirty oxygen sensor, dirty fuel injectors, or bad spark plugs can be the cause. I'm going for an oil change this week as well just to rule that out. My tires are still good and are properly inflated, and I don't have a stuck brake caliper.

This huge drop in mpg is very odd to me and I was wondering if there is something I'm missing that would cause all this. Particularly the large drop in the electric motor's usage in eco mode. Anyone have any ideas?
Have a look if there are many more cold starts relative to earlier. Cold starts and short distances cause a big increase in fuel consumption.
 

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Discussion Starter #5
Have a look if there are many more cold starts relative to earlier. Cold starts and short distances cause a big increase in fuel consumption.
How cold would you consider a cold start, in terms of temperature? I live in Florida so our "Winters" are hardly cold. The lowest I've ever started the car in is only 45 degree weather, and that was maybe 3 times total. I typically drive 1-2 miles a day of city driving now, compared to what was about 30 miles of highway/city before I moved in early January. Even still, is a drop off of 10mpg really expected for these conditions?
 

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After a 'not short' drive, place your hand on each wheel center. If one feels noticeably warmer than the others, check for a dragging disc brake on that wheel. I have a cheap Craftsman infrared temperature read out that I use in the kitchen. Works great for this purpose and you can aim it at the brake discs to see major differences.
 

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After a 'not short' drive, place your hand on each wheel center. If one feels noticeably warmer than the others, check for a dragging disc brake on that wheel. I have a cheap Craftsman infrared temperature read out that I use in the kitchen. Works great for this purpose and you can aim it at the brake discs to see major differences.
I'll have to check for that again, because something like that is the only thing that would make sense to me for such a big drop.
 

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An update:

I went in for my Oil Change yesterday, I got the commended 0W-20 Full synthetic oil. I also topped off my tank, and started using eco mode again. I reset my MPG data to see if there was any difference.With some city driving of less than 10 miles since I filled up, I've hardly broken 30MPG. I'm still noticing a seriously lack of power on the low end, and the electric motor is still hardly used. Even when the left gauge's needle is directly on Eco,the MPG display hardly crosses 30, and the energy screen doesn't show the electric motor doing anything. Even when the battery is over half full. I'm still at a loss of what can cause such a ridiculous change in performance, both in power and MPG. Anyone have any ideas?
 

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An update:

I went in for my Oil Change yesterday, I got the commended 0W-20 Full synthetic oil. I also topped off my tank, and started using eco mode again. I reset my MPG data to see if there was any difference.With some city driving of less than 10 miles since I filled up, I've hardly broken 30MPG. I'm still noticing a seriously lack of power on the low end, and the electric motor is still hardly used. Even when the left gauge's needle is directly on Eco,the MPG display hardly crosses 30, and the energy screen doesn't show the electric motor doing anything. Even when the battery is over half full. I'm still at a loss of what can cause such a ridiculous change in performance, both in power and MPG. Anyone have any ideas?
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Could be a few things. Could have a bad plug or clogged injector but I would also take a look at your batteries. Some have mentioned big increases after replacing the engine battery (not the hybrid battery) as they continue to function long past peak efficiency in this type of vehicle. it could also be a mass airflow sensor issue, bad gas, an alignment issue, something with the tranny or computer... there are many possibilities sadly. Let me know if you get it fixed and there is a definitive answer as to the cause.
 

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Could be a few things. Could have a bad plug or clogged injector but I would also take a look at your batteries. Some have mentioned big increases after replacing the engine battery (not the hybrid battery) as they continue to function long past peak efficiency in this type of vehicle. it could also be a mass airflow sensor issue, bad gas, an alignment issue, something with the tranny or computer... there are many possibilities sadly. Let me know if you get it fixed and there is a definitive answer as to the cause.
Interesting that the 12V battery can have an effect. I'm not sure if the car has ever had it replaced so it might be worth looking to that as well. Alignment seems to be a non-issue, as the car doesn't pull in any one way. A clogged injector could make some sense as well, or an airflow sensor issue. I'm using the same 85/87 octane normal gas I always have, back when I was getting much more normal numbers. I'm really hoping it isn't the transmission, as that would be such an expensive fix. As for the computer, I did install a remote starter to the car, so I'll have to see if that messed with anything. I've hardly used the remote starter, but as spring ramps up here I will be more.
 

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Ground straps can have a Significant effect on your system.. Significant..

Like “boom” i have a new car all over again..

check your straps, add a strap if unsure.. Look for any white at point of mount..

if your closer to the water down there, the air quality has a significantly higher mineral content and promotes oxidation of electrical connections..

And Yes the heater is a big draw on the system, although you generally don’t use it down in Florida, it is a Reactive load on the system, not an inductive load
 

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What
Ground straps can have a Significant effect on your system.. Significant..

Like “boom” i have a new car all over again..

check your straps, add a strap if unsure.. Look for any white at point of mount..

if your closer to the water down there, the air quality has a significantly higher mineral content and promotes oxidation of electrical connections..

And Yes the heater is a big draw on the system, although you generally don’t use it down in Florida, it is a Reactive load on the system, not an inductive load
What are ground straps, are you referring to electrical ground? Where would I find those?
 

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How cold would you consider a cold start, in terms of temperature? ... I typically drive 1-2 miles a day of city driving now, compared to what was about 30 miles of highway/city before I moved in early January. Even still, is a drop off of 10mpg really expected for these conditions?
A cold start is every time the engine starts when it is not already hot from recent running. Every cold start hits fuel consumption significantly. The engine runs to get up to temperature, but most of the motive force is supplied by the battery for the 1st mile or so. The CT only starts running in it's normal efficient mode after a few miles.

Running 1 to 2 miles only is a huge increase in cold starts per mile. This could easily be the sole reason for your increase in fuel consumption.
 
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