Hybrid mpg dropping

[heyjewel]

Hello. 2014 mkZ hybrid with 165,000 miles.  MPG has always been around 40.  Past few weeks has steadily dropped to 39.0  Any ideas why?

[bbf2530]

18 minutes ago, heyjewel said:

Hello. 2014 mkZ hybrid with 165,000 miles.  MPG has always been around 40.  Past few weeks has steadily dropped to 39.0  Any ideas why?

 

Hi heyjewel. That is only a difference of ~2.5%. It is negligible (even well within the margin of error), and could be due to anything. Higher ambient temperatures. Increased use of A/C. Slight differences in the driving environment which you would not even notice...etc., etc. It is nothing to be concerned about unless it keeps dropping at a higher rate.

 

Keep us updated and good luck.

Edited July 15, 2023 by bbf2530

[heyjewel]

Thanks for reply.  Yeah it's small but still dropping.  Wondering if a 'tuneup' will help?  Wondering if nightmare scenario of batteries getting old might be problem?  

 

[bbf2530]

19 hours ago, heyjewel said:

Thanks for reply.  Yeah it's small but still dropping.  Wondering if a 'tuneup' will help?  Wondering if nightmare scenario of batteries getting old might be problem?  

 

 

Hi heyjewel. The first place to look would be a change in driving habits and/or environment. For example...seasonal changes in driving environment. If the temperatures lately are hot where you are, and you are using the A/C more than previously, that will result in a significant drop in fuel mileage for the season. Sometimes up to 25%.

 

Another variable would be if you are driving more highway miles lately. Since the hybrid also uses regenerative braking to recharge the batteries, highway miles can result in a mpg hit, since it will result in less regenerative braking/more ICE engine usage, and thus...the possibility of lower fuel mileage. 

 

There are many other variables, but you get the idea. 

 

It is impossible to accurately determine if a "tune-up" will help, since that would depend on whether it is a tune-up curable type of issue.  When was your last tune-up (plugs, engine air filter etc.)?

Plugs are usually required to be changed at 100,000 miles on the ICE engines. I am not sure about the Hybrid, it may be the same or not. It would be good to change the engine air filter every 30,000 miles.

 

You can find the Hybrid Maintenance Schedule in your Owners Manual. If the plugs or engine air filter etc. are due for a change, change them. 

 

All in all, a 2.5% drop in fuel mileage is usually not something to worry about. So keep an eye on it to see if it continues to drop precipitously.

 

Keep us updated and good luck.

 

Edited July 16, 2023 by bbf2530

[17MKZ3.0TT]

On 7/16/2023 at 10:38 AM, bbf2530 said:

 

Hi heyjewel. The first place to look would be a change in driving habits and/or environment. For example...seasonal changes in driving environment. If the temperatures lately are hot where you are, and you are using the A/C more than previously, that will result in a significant drop in fuel mileage for the season. Sometimes up to 25%.

 

Another variable would be if you are driving more highway miles lately. Since the hybrid also uses regenerative braking to recharge the batteries, highway miles can result in a mpg hit, since it will result in less regenerative braking/more ICE engine usage, and thus...the possibility of lower fuel mileage. 

 

There are many other variables, but you get the idea. 

 

It is impossible to accurately determine if a "tune-up" will help, since that would depend on whether it is a tune-up curable type of issue.  When was your last tune-up (plugs, engine air filter etc.)?

Plugs are usually required to be changed at 100,000 miles on the ICE engines. I am not sure about the Hybrid, it may be the same or not. It would be good to change the engine air filter every 30,000 miles.

 

You can find the Hybrid Maintenance Schedule in your Owners Manual. If the plugs or engine air filter etc. are due for a change, change them. 

 

All in all, a 2.5% drop in fuel mileage is usually not something to worry about. So keep an eye on it to see if it continues to drop precipitously.

 

Keep us updated and good luck.

 

Everything bbf2530 said is spot on, and just a change in gas stations could change it that month. Assuming normal maint. has been done, tire psi is good,  and nothing happened that could have whacked your front end alignment out a little, 1 mpg is hard to track down.