Fuel economy deteriorating??

[utekineir]

Op. Is it cold where you live?

[Bonburner]

.. really 1 mpg difference lol
depending on how i drive for the tank i've ranged from 32 down to 24 mpg. lol

[SloS14]

[radroach]

Haven't people reported fuel trims changing over time on their tune? I've heard people going back over data logging and retuning.

[Kelbyat07]

Originally Posted by radroach

Haven't people reported fuel trims changing over time on their tune? I've heard people going back over data logging and retuning.

Yeah I think I read the same thing and also something about resetting..

[mikalem]

Also would wonder, who gets a tune and doesn't give it the beans for a few days after the fact just for funzies? Even a 4 - 5 average distance drop wouldn't be all that alarming - I'd say either winter gas, or in-car avg needs reset and run for a few tanks. (Didn't mention either if the user switched to E85.... that would do it too )

[m.wood0213]

Originally Posted by Poodles

Tire pressure is out because of the TPMS system. It's more likely the winter blend gasoline.

my tpms didnt trigger in winter til it dropped to 25psi (10psi drop).

Winter grade gas and colder tires can result in 1mpg drop or 1 more spirited drive or 1 more redline or 1 more hill or any number of things. dont sweat it just drive it and enjoy it!

[Frost]

I have always tracked my fuel econ and I noticed the following:

- Outdoor Air Temps (OAT) will affect mileage. Usually anything under 4-5 deg C will have an impact on your MPG.
- Tire pressures, drops in 2-3 psi will begin to have an impact. OAT will also affect tire pressure so keep an eye on that too, it's a cascading effect. You lose pressure because it is cold and you also lose fuel econ because it is cold!

Right now with Toronto going through a deep freeze spell, my fuel econ has been around 6.8L/100km which is on the bad end. Yet come summer, when I drive to say, Quebec City, I will get 5.5L/100km.

So long story short, check your tire pressures, check your OATs and check your right foot. If all of that is in check, then start suspecting engine issues.

[Poodles]

Originally Posted by m.wood0213

my tpms didnt trigger in winter til it dropped to 25psi (10psi drop).

Winter grade gas and colder tires can result in 1mpg drop or 1 more spirited drive or 1 more redline or 1 more hill or any number of things. dont sweat it just drive it and enjoy it!

Ouch, that's a pretty big drop, most cars are a bit more strict.


Anyway, yeah, you'll lose fuel economy from the cold because it takes longer to warm up (cold start enrichment) plus the air tends to be denser so you make a bit more power and with that comes fuel use. There's just a whole lot going on during winter that causes crap gas milage.


Summer around here is pretty damn bad too (over 100F)

[newbrz]

Originally Posted by humfrz

Hi ya newbrz .....

Let's see if I'm understanding you correctly. Your fuel mileage has dropped from 27 to 26 MPG .... ??

Or, dropped 4-5 MPG .. ??

If it's the former, that just could be within experimental error. Or, that winter blends of gasoline sometimes yield less fuel economy. Or, like mentioned, tire air pressure might be a bit lower.

How are you checking your mileage (calculation vs. the onboard monitor)?

humfrz

sorry I havent checked the forum in a long time. The AVERAGE dropped 1MPG due to the issues I have been experiencing. I have 18k miles on the car and I think 1mpg drop is a lot considering it is average what I am talking about. The 4-5mpg drop is by comparing using cruise control at a certain speed, I used to put my car at 85mph and the consumption was at about 31mpg and is not around 27. I live in florida, so cold weather and hills are not the reason. I did full fluid changes recently and it improved a little but before it I tried tire pressure, putting more motor oil, better gasoline, etc.

[newbrz]

Originally Posted by Pizzman

Cruise control is not efficient, especially on hills, that with tire pressure, and driving style are the other options. You would hear and or feel (if you are one with your car. IE bearings or trans)any mechanical issues that would result in heavy fuel consumption. Also are you running the recommended oil. That would f up your mpgs as well. Take it in for service if none of these sound like a problem.

I live in Florida so the hills are not much a problem on it. I did the service and got better in such way that it does not concern me as much anymore. Nevertheless I had tried all except the service before I even posted the thread. Thanks for your help

[humfrz]

Originally Posted by newbrz

sorry I havent checked the forum in a long time. The AVERAGE dropped 1MPG due to the issues I have been experiencing. I have 18k miles on the car and I think 1mpg drop is a lot considering it is average what I am talking about. The 4-5mpg drop is by comparing using cruise control at a certain speed, I used to put my car at 85mph and the consumption was at about 31mpg and is not around 27. I live in florida, so cold weather and hills are not the reason. I did full fluid changes recently and it improved a little but before it I tried tire pressure, putting more motor oil, better gasoline, etc.

Well, newbrz, I would consider +/- 1 MPG within "experimental error".

After all we are dealing with a machine and many factors can affect its efficiency.

I have found (the hard way) during my 71 years, that certain things in life are just not worth worrying about ....


humfrz

[Poodles]

IIRC even Florida goes to a winter blend which will lower your gas mileage.

[strat61caster]

Here's why everyone is telling you not to worry:

You're stating that your average dropped 1 mpg, that is literally the least concern ever.

What you mean is that your average for the first 18k miles was in the area of 27 mpg. Over the recent few months your average has been so low that it's dropped your 18k average down by nearly a point. That is big. But nobody will understand unless you post something like the following:
First 18k miles average 27 mpg
18k-20k averaging 20 mpg

Even then it could easily make sense if you start driving in the city a lot, you're used to the car so you open it up a bit more (your car may not be heavier but your foot may be), or as others suggested winter blend gasoline combined with cold temperatures lead to a noticeable drop in fuel efficiency. Hope you figure it out.