Truck question

[Toledo Mark]

I have a 2002 Dodge Dakota with a 4.7.  It has 155k miles on it.  I only drive it in the winter as the Valk is parked.  Anyway I noticed this week that my mileage cruising at 55mph seems to only be about 16MPG.  When I drove the truck year round it would run as high as 21MPG.

It has an onboard computer that shows MPG while driving.

I have cleaned the K&N filter and would like to know what anyone would recommend to try and improve.  What do they do for a tune-up?  Plugs? Wires?  Not to truck savvy here.

Or could it just be the cold weather and gas?

Any thoughts?

Thanks

[sandy]

If the oxygen sensor goes out, fuel economy usually goes South real bad. I'd have a pro put an engine tester on it. Check the computer codes.

[olddog1946]

I used to have an extended cab dakota with that same motor...never got any better than 17mpg..it was a 4x4...so you may not have a problem..to be honest I doubt you have any codes being set either..if you do, try to get them taken care of..if not, drive it..you may find that as the weather improves so does the mileage.

[Bobbo]

16-18 MPG sounds about right for a Dakota 4.7 with that mileage.  Is it possible that your gas station has converted from 100% gasoline to E10, or switched to cold weather additives?  That will drop your mileage a few MPG.  Cleaning the air filter won’t really affect gas mileage on a closed loop fuel injected system.  If your “check engine” light is on, you can look for OBDII codes.  Changing the plugs won’t hurt, especially if they have 100K+ miles on them.

[sugerbear]

a can of techron wouldn't hurt either.

[RoadKill]

16-18 MPG sounds about right for a Dakota 4.7 with that mileage.  Is it possible that your gas station has converted from 100% gasoline to E10, or switched to cold weather additives?  That will drop your mileage a few MPG.  Cleaning the air filter won’t really affect gas mileage on a closed loop fuel injected system.  If your “check engine” light is on, you can look for OBDII codes.  Changing the plugs won’t hurt, especially if they have 100K+ miles on them.

Not cleaning your air filter would just be DUMB... Every engine is an air pump. Air in...Air out.
It must get really lonely being the only smart person in the universe Bobbo. Thick,cold oil in your differential/trans etc...would make more of a difference than the dreaded 10% ethanol in the tank.

Closed loop basically means that the truck computer it adjusting the fuel mixture based on load/temperature/air flow and several other inputs. When it's cold the computer gives it more fuel. Just like you need more "choke" on a cold engine.  Mostly simplified into layman terms, a clean air filter will defiantly help but Bobbo is correct that if the check engine light is on...it's got a problem and sucking more fuel than necessary.

[Brad]

If the oxygen sensor goes out, fuel economy usually goes South real bad. I'd have a pro put an engine tester on it. Check the computer codes.

On that year if an O2 sensor is bad the check engine light should be on.

[Varmintmist]

if the check engine light is on...it's got a problem and sucking more fuel than necessary.

If it was a Chebby and the check engine light was on, that means the truck is running. Since its not, Autozone will plug in a diagnostic for free.

[R J]

I have a 2002 Dodge Dakota with a 4.7.  It has 155k miles on it.  I only drive it in the winter as the Valk is parked.  Anyway I noticed this week that my mileage cruising at 55mph seems to only be about 16MPG.  When I drove the truck year round it would run as high as 21MPG.

It has an onboard computer that shows MPG while driving.

I have cleaned the K&N filter and would like to know what anyone would recommend to try and improve.  What do they do for a tune-up?  Plugs? Wires?  Not to truck savvy here.

Or could it just be the cold weather and gas?

Any thoughts?

Thanks

My 05 with 97K when I traded it off had averaged 15.7 for it's lifespan in my garage.    I'd guess it had pulled a trailer for 10K of that time.  So yours sounds about right to me.

PS:  10% ethanol never effected it in the mileage dept.

[mattfidaho]

16-18 MPG sounds about right for a Dakota 4.7 with that mileage.  Is it possible that your gas station has converted from 100% gasoline to E10, or switched to cold weather additives?  That will drop your mileage a few MPG.  Cleaning the air filter won’t really affect gas mileage on a closed loop fuel injected system.  If your “check engine” light is on, you can look for OBDII codes.  Changing the plugs won’t hurt, especially if they have 100K+ miles on them.

Not cleaning your air filter would just be DUMB... Every engine is an air pump. Air in...Air out.
It must get really lonely being the only smart person in the universe Bobbo. Thick,cold oil in your differential/trans etc...would make more of a difference than the dreaded 10% ethanol in the tank.

Closed loop basically means that the truck computer it adjusting the fuel mixture based on load/temperature/air flow and several other inputs. When it's cold the computer gives it more fuel. Just like you need more "choke" on a cold engine.  Mostly simplified into layman terms, a clean air filter will defiantly help but Bobbo is correct that if the check engine light is on...it's got a problem and sucking more fuel than necessary.

I agree that not cleaning your air filter is dumb... but... on new computer controlled fuel systems compensate for less air flow, so it shouldn't effect your MPG if the air cleaner is getting dirty.

"Back when cars had carburetors, changing your air filter could have helped. Today, the on-board computer injects exactly the amount of gas your car needs. A small restriction in the air flow won't make the engine run too rich. The pleated-paper air filters used today are very large, and can hold a lot more dirt than you might think before they start to choke the engine. An oily filter--the result of blow-by fumes from the crankcase--can make a filter plug up pretty fast. Modern crankcase ventilation systems are far less prone to oil them up than they used to be.

Still, that filter probably won't affect mileage until it's so plugged that it makes the Check Engine light come on. But if you have an older car or truck, or any equipment that still uses a carburetor, it is important to keep an eye on the air filter, to make sure its free-flowing. "

http://www.popularmechanics.com/cars/how-to/4264939

[fudgie]

Clean your filter like Rkill says. I just looked at mine the last few years but was really surprised when I washed it. Alot of little particles. I should have cleaned it more in 4 years then once.  Tune up would help alot to. Did Kits this winter and her mpg increased.

[Bobbo]

16-18 MPG sounds about right for a Dakota 4.7 with that mileage.  Is it possible that your gas station has converted from 100% gasoline to E10, or switched to cold weather additives?  That will drop your mileage a few MPG.  Cleaning the air filter won’t really affect gas mileage on a closed loop fuel injected system.  If your “check engine” light is on, you can look for OBDII codes.  Changing the plugs won’t hurt, especially if they have 100K+ miles on them.

Not cleaning your air filter would just be DUMB... Every engine is an air pump. Air in...Air out.
It must get really lonely being the only smart person in the universe Bobbo. Thick,cold oil in your differential/trans etc...would make more of a difference than the dreaded 10% ethanol in the tank.

Closed loop basically means that the truck computer it adjusting the fuel mixture based on load/temperature/air flow and several other inputs. When it's cold the computer gives it more fuel. Just like you need more "choke" on a cold engine.  Mostly simplified into layman terms, a clean air filter will defiantly help but Bobbo is correct that if the check engine light is on...it's got a problem and sucking more fuel than necessary.

No one is suggesting skipping simple maintenance items like cleaning or replacing the air filter.  Replacing items like filters, plugs, and belts are preventative maintenance, not to correct a problem after it has occurred.  Lonely?  Hardly.  Every educated auto technician knows these things.

[Marcel]

Additive package for Gas in the Winter is different than it would be in warm weather.

SO mileage will go down this time of year and no I don't know anyway to compensate for your

problem except it will get better this spring.

Not many people consider the gas additives package but just simply start repalcing parts without any

improvement.

So there.

[Dogg]

there is nothing wrong with 17mpg with that motor. 4.7 are underpowered ina heavy truck. cold weather additives will cut into your mileage a tiny bit, but not that much. if the mil light aint on, just keep driving it. try to let it warm up before heading out tho. cold weather loads eat the motors alive...

[highcountry]

My Corolla goes from 37 mpg to 33 mpg in the winter because the "winter" gas and higher rpm and longer idle time when started in the cold.  I think the gas is the biggest contributor.