My 96 Jeep Cherokee 4.0L is getting crap for gas mileage lately. The temps have been in the teens for a while. I know in the winter time they run a different gas around here. The motor runs fine and has plenty of power, but I did notice last week that while I was loading some wood up at Lowe's it started to idle rough. When I got in and put it in gear to take off it was as if it was misfiring, like a plug was fouled. I got on the gas a little and it cleared up and hasn't come back since. I'm wondering if my O2 sensor is on it's way out. I think it's the original with 113,000 miles on it. Perhaps it's time to pry open my wallet and get a new one. I believe it's after the cat. The other (in the header) was replaced when I installed the Borla header.
Bad gas mileage because of cold weather??
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Yup. I track the fuel economy on both my vehicles and they get worse the farther down the mercury goes. I usually get about 18-19mpg in my Taurus (90% city) and I just tracked a whopping 14.4mpg. It was only -22F out though.
Lots of things going on in cold weather that drives fuel econmy down.
Cold air is slightly denser, requires a bit more fuel to burn cleanly (and of course produces a bit more power). That consumes a bit more gas.
Longer warm up times mean more time running in open loop, ignoring the 0xygen sensor. Keeps the engine running richer longer, consuming more gas.
More idiling also tends to come with cold weather as people let their car "warm up", consuming more gas.
All the lubricants are thicker when cold, producing more drag until the warm up. This includes motor oil, transmission fluid, differential oil, even the grease in the driveline! That consumes more gas.
Lots of use of the heater on full blast, defrosters, etc... The electricity comes from somewhere - from the alternator driven by the engine which, you guessed it, uses more gas.
In colder weather, the air pressure in your tires drops. Do you check the sir pressure for every 10 F change in temp? At very cold temps, every 10 F can mean 2-3 psi lost. Underinflated tires require more energy to push giving more fuel consumed.
Yet some people blame all these losses on "winter fuel". Winter fuel IS an issue in some places. You will know if it is if you find a significant drop in fuel economy only when the fuel changes. In many places, (like where I live), the energy content of winter gasoline is basically no different than summer.
So you don't feel bad, my '88 Cherokee averages 16.7 mpg. It peaks in the summer at nearly 19 mpg in July, but only avrages 14.2 mpg in January.
At least it beats my truck - I average 13.2 mpg in January in my '99 F150. The truck averages 15.5 mpg, and peaks at nearly 17.5 mpg in July.
Cold air is slightly denser, requires a bit more fuel to burn cleanly (and of course produces a bit more power). That consumes a bit more gas.
Longer warm up times mean more time running in open loop, ignoring the 0xygen sensor. Keeps the engine running richer longer, consuming more gas.
More idiling also tends to come with cold weather as people let their car "warm up", consuming more gas.
All the lubricants are thicker when cold, producing more drag until the warm up. This includes motor oil, transmission fluid, differential oil, even the grease in the driveline! That consumes more gas.
Lots of use of the heater on full blast, defrosters, etc... The electricity comes from somewhere - from the alternator driven by the engine which, you guessed it, uses more gas.
In colder weather, the air pressure in your tires drops. Do you check the sir pressure for every 10 F change in temp? At very cold temps, every 10 F can mean 2-3 psi lost. Underinflated tires require more energy to push giving more fuel consumed.
Yet some people blame all these losses on "winter fuel". Winter fuel IS an issue in some places. You will know if it is if you find a significant drop in fuel economy only when the fuel changes. In many places, (like where I live), the energy content of winter gasoline is basically no different than summer.
So you don't feel bad, my '88 Cherokee averages 16.7 mpg. It peaks in the summer at nearly 19 mpg in July, but only avrages 14.2 mpg in January.
At least it beats my truck - I average 13.2 mpg in January in my '99 F150. The truck averages 15.5 mpg, and peaks at nearly 17.5 mpg in July.
Patman
Staff member
My gas mileage is down a lot this winter, from 20 MPG down to 16-17. I use my block heater every morning, and at work I'm in an underground garage which stays between 40-50F most of the time.
So why is my mileage so low? Two words: TRAFFIC JAMS! I've gotten stuck in so much bad traffic this winter it's not funny. We seem to get hit with all kinds of little snow storms lately, just enough to make my trip home from work take as long as 2 hours (and it's only 25 miles!)
So why is my mileage so low? Two words: TRAFFIC JAMS! I've gotten stuck in so much bad traffic this winter it's not funny. We seem to get hit with all kinds of little snow storms lately, just enough to make my trip home from work take as long as 2 hours (and it's only 25 miles!)
Yep, there is little difference in winter versus summer gasoline here in the Twin Cities. There is a bit of a change to deal with evaporative properties, but it isn't like many markets where oxy fuel is used one season and not the other.
For those who don't know, Minnesota requires the use of 10% ethanol statewide year around in nearly all gasoline. Its been that way since around 1996.
I buy my gas all over. I have a 30 mile commute to work, so I see a lot of stations. My F150 seems to prefer Phillips 66, and I tend to buy at the Gardenview/42 location, the Cedar /155th St location and I-35E / Pilot Knob locations. After that, Kwik Trip and Holiday gets put in the most. The Jeep couldn't care less what it runs, so whatever is cheapest goes in the tank.
Patman has one item that still drops fuel mileage - traffic.
While the block heater heats the engine fluids, little is being done to anything else in the driveline, like the tranny and differentials. Those are still "thick" sucking power away.
No matter what you do, there are still going to be a few things, like the air temp/density relationship that you can't do anything about.
In my Fuel records, its pretty clear there isn't a big change between winter and summer blends here. There are no massive drops in mpg just related to the date. Instead, I get the nice looking curve, up and down, with no real irregularities.
For those who don't know, Minnesota requires the use of 10% ethanol statewide year around in nearly all gasoline. Its been that way since around 1996.
I buy my gas all over. I have a 30 mile commute to work, so I see a lot of stations. My F150 seems to prefer Phillips 66, and I tend to buy at the Gardenview/42 location, the Cedar /155th St location and I-35E / Pilot Knob locations. After that, Kwik Trip and Holiday gets put in the most. The Jeep couldn't care less what it runs, so whatever is cheapest goes in the tank.
Patman has one item that still drops fuel mileage - traffic.
While the block heater heats the engine fluids, little is being done to anything else in the driveline, like the tranny and differentials. Those are still "thick" sucking power away.
No matter what you do, there are still going to be a few things, like the air temp/density relationship that you can't do anything about.
In my Fuel records, its pretty clear there isn't a big change between winter and summer blends here. There are no massive drops in mpg just related to the date. Instead, I get the nice looking curve, up and down, with no real irregularities.
I almost always use the block heater in my car if it's 30F or colder out since I only drive 7 miles one way to work. I check the tires in my vehicles at least every two weeks and I may have to put 1-2 psi in each tire.
MNgopher- which gas stations do you usually fill up at? I've been going to the Phillips 66 at Cty 42 and Gardenview in Apple Valley or the Kwik Trip at the Cty 11/ I35W exit. I know there's no real difference between the summer and winter gas here in MN (they always contain 10% ethanol, correct?) but there's no reason why I should see a 3 mpg decrease driving the same routes.
MNgopher- which gas stations do you usually fill up at? I've been going to the Phillips 66 at Cty 42 and Gardenview in Apple Valley or the Kwik Trip at the Cty 11/ I35W exit. I know there's no real difference between the summer and winter gas here in MN (they always contain 10% ethanol, correct?) but there's no reason why I should see a 3 mpg decrease driving the same routes.
Patman
Staff member
That is an excellent point! It's especially true for rear drive cars that use 75w90 or 85w90 fluid in their differentials.
Lots of factors at play here; I agree, temperature plays a big role. Fuel economy seems to really suffer when the temperature is below freezing.
With my '02 SAAB 9-5 Aero (EPA 22 city/31 hwy), I got the best mileage ever last September, 35 mpg on a trip to Toronto. It was probably around 72°F.
But a few weeks ago, I drove up to Vermont, and despite using a thinner engine oil (GC instead of M1 0W-40) I only got 26 mpg!
I figure these factors are to blame:
-extreme cold (the VT trip was at -14°F/-26°C!)
-ethanol in the winter fuel
-snow tires
I think it makes a big difference if the mercury is above the freezing point--yesterday it was about 38°F and I was getting closer to 30 mpg despite a lead foot on the NJ Tpke!
ps- doing the math, my figures show a 25% difference--about the same percentage difference as road_rascal's. Very interesting!
With my '02 SAAB 9-5 Aero (EPA 22 city/31 hwy), I got the best mileage ever last September, 35 mpg on a trip to Toronto. It was probably around 72°F.
But a few weeks ago, I drove up to Vermont, and despite using a thinner engine oil (GC instead of M1 0W-40) I only got 26 mpg!
I figure these factors are to blame:
-extreme cold (the VT trip was at -14°F/-26°C!)
-ethanol in the winter fuel
-snow tires
I think it makes a big difference if the mercury is above the freezing point--yesterday it was about 38°F and I was getting closer to 30 mpg despite a lead foot on the NJ Tpke!
ps- doing the math, my figures show a 25% difference--about the same percentage difference as road_rascal's. Very interesting!
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