Bad Fuel Mileage

[rob28]

Greetings,

I'm new here and I need some advice. I have an 02 P5 and I have noticed lately that my fuel economy has dropped significantly. I know that having a little colder weather can have an effect but wow - I've never seen it drop like this. Recently I changed the oil and air filter. Is there a pcv valve? Could that be the problem? What about resetting the computer by unhooking the battery - should I try that?

Many thanks,

Rob

[falsedawn]

Define "significantly", and over how many miles are you taking your mpg average?

Welcome to the forum BTW!

[Mr. Win]

Any cels? Reseting the ECU will prob give you worse until the ECU re learns everything.

[maxek]

This is very normal with our car. I dropped ~10 miles to a gallon. It is cold air and if you have CAI installed like I do then you f.... Like I am.

[Diehonda]

Start cheap and check your plugs and run some Seafoam thru your gas. It is most likely due to the cold temperatures, driving with the heat on, and not letting it warm up fully.

My CAI has decreased my mpg a bit but the fun part is watching my temp go up and down depending on speed and amount of freezing arse air being sucked in. It never drops below 155 though.

[NJP5Guy]

(blah) (deadhorse

[rob28]

Start cheap and check your plugs and run some Seafoam thru your gas. It is most likely due to the cold temperatures, driving with the heat on, and not letting it warm up fully.

My CAI has decreased my mpg a bit but the fun part is watching my temp go up and down depending on speed and amount of freezing arse air being sucked in. It never drops below 155 though.


I'll check that tomorrow. Thanks to all for the feedback. I also found some information about SRI's. I used to use a CAI but I removed it because the filter was to hard to get at in the wheel well.

I don't know much about SRI's other than what I have read on this site. They sound like an easy install but I don't know the cost.
Rob

[mogi]

not only does cold weather affect it, but winter blend gas in many regions really sucks!

my mileage dropped about 8MPG this winter, going to try and bump up to the next grade of gas to see if there are a bit less cleaners in the blend...

octane ratings are a strange science, it is actually an averaging of numbers, so 87 in the summer isn't the same as 87 in the winter from what I have been reading

[Protege52003]

up here in the northeast we have a different blend of gas in the winter, which hurts milage a little. i think a lot of people let their cars warm up in the cold months. does not really hurt the P5, but when i let the jetta warm up it seems to burn more gas??????

my milage stays about the same thoughout the year......25 mpg on my average driving!

[Diehonda]

My jetta's air pump and rich fuel blend during cold months burned thru gas really bad. A lot worse then my 5.

What could be done to conteract the winter blend gas, if anything?


Have you had time to check anything out on your car yet to see yet?

[worker_robot]

do you guys have the 99-04 model jetta? apparently you don't have to let those warm up, but i've heard the opposite from valvoline guys (when i had my jetta).

thankfully i'm a proud (newish - 1 month!!) owner of a PR5 now so i don't have to worry about the craptacular jetta anymore! but i guess the relevant question is - how long (if at all) should we warm up the protege5s in these northeastern winters? (0-32 deg. F) and does it help?

[bazooka joe]

up here in the northeast we have a different blend of gas in the winter, which hurts milage a little. i think a lot of people let their cars warm up in the cold months. does not really hurt the P5, but when i let the jetta warm up it seems to burn more gas??????

my milage stays about the same thoughout the year......25 mpg on my average driving!

my avg taken yesterday was 23 with min boostin

[Diehonda]

do you guys have the 99-04 model jetta? apparently you don't have to let those warm up, but i've heard the opposite from valvoline guys (when i had my jetta).

thankfully i'm a proud (newish - 1 month!!) owner of a PR5 now so i don't have to worry about the craptacular jetta anymore! but i guess the relevant question is - how long (if at all) should we warm up the protege5s in these northeastern winters? (0-32 deg. F) and does it help?


99.5 and yes I did have to or I would burn thru 02 sensors left and right due to the rich fuel. plus the oil would be too cold still. Craptacular! That is great. And right on the money, as there are so many expensive repairs. I still miss mine for some reason though.

I let my 5 warm up for about five to seven minutes to have the temp read about 150 and it only take about three or four minutes of driving to be up to 185. That is with outside temp of between 23 and 35. Any lower temp and I let it warm up a bit longer.

I also do not turn my heat on until it reads 150 because it slows the warm up period.

[Reitrof]

my avg taken yesterday was 23 with min boostin

Hmm, mine yesterday was 32. (poke)

[bazooka joe]

Hmm, mine yesterday was 32. (poke)

that was of course both hiway and local driving...and my highway is like driving through a parking lot full of cars after a patriots game...Stop and Go!!

[Protege52003]

Hmm, mine yesterday was 32. (poke)

mark's if FI'd though as you know......



My jetta's air pump and rich fuel blend during cold months burned thru gas really bad. A lot worse then my 5.

What could be done to conteract the winter blend gas, if anything?


Have you had time to check anything out on your car yet to see yet?


my jetta is an 04 with under 10K miles......

[Reitrof]

that was of course both hiway and local driving...and my highway is like driving through a parking lot full of cars after a patriots game...Stop and Go!!

I know, I just couldn't resist. Mine is mostly higway with some local driving(75/25 mix). My worst gas mileage was 23-25 and that was towing a 16' boat.

[i12drivemyMP5]

This may be due to how much or how little ethanol is mixed in the gas. Some places are 10% on normal basis & some states are shooting for 20% mix. Lots of good fuel related info on smartgas.net.

[03MzdSpdSTP]

if you are getting 5mpg lower then usual, try swapping out the 02 sensor. if its starting to go bad, it won't throw a CEL.

[Pesty]

Another thing to keep in mind is that unless you have modded it, if you have the AC set to defrost it turns on the compressor. Basically the same as running with the AC on.