weather drop=dramatic mpg drop-is it normal with cherokees???

[ironman2712]

hello everyone, i have had my cheroo for sth like 6monts,so it will be our first winter,,, recently i noticed dramatic increase in fuel consumption (4.0, 6in line), caused by weather temp.drop( arround 0 C)-from20mpg-to around 10mpg.I allready covered front grill with some plastic pads, so it reaches after a few minutes normal aperating temp( arround 200F), but still mpg didn't change( i did not have that problem in summer time-all was ok)-is it normal with cherokees???
Do i have to prepare my jeep to extreme winter time( it's gonna be 20C bellow soon) and if yes -how to do it and what to preapare for????( what to do with fluids, fuel (any adds on), filters ant first few minutes after starting the engine)...please help

[JIMMY92w]

My 89 Jeep Comanche 4.0L 4x4 has had no fuel drop and its been out in +20c and -20c. However, in winter, when the snow is down, and using four wheel drive for traction, the engine is powering both front and rear wheels so that extra load will decrease fuel mileage.

Another factor that may cause a drop is the oil viscosities in your engine and drive line. Cold fluids run slow until normal operating temps are reached. That extra friction will have an impact on fuel mileage.

Viscosity is the resistance of a liquid to flow. Low viscosity fluid is water, a high viscosity fluid is vegetable oil.

Also to note synthetics vs conventional oil. Conventional oil gains viscosity (thicker) due to cold weather where-as synthetics are able to remain more consistent in changing temperatures (will pour at almost the same rate in +20c to -20C)

What would be ideal is synthetic oils in your front and rear differentials, transfer case, transmission, and engine.

*** please do your research about synthetics and leaks (smaller molecule size of synthetic leaks through hole where as larger molecule of conventional cannot drip through that same hole) and on changing an older automatic trans fluid with new fluid causing catastrophic transmission failure.

You can install various heaters in your engine compartment to help with cold weather start up.
Block heater: Heats engine block coolant so engine heats up faster
Battery heater, and Oil pan heater

One other note, check your tire pressures as cold temperatures tend to reduce air volume where as hot temperatures increase tire pressure... Low volume = Less MPG


Now Please read my post on DRIVE LINE WINED-UP, a few below yours, and answer a simple YES, NO, or Never Noticed, but maybe...PLEASE,


Mike

[fredjacksonsan]

Although the weather, fluids, and gasoline formulation can affect your mpg, it's usually only 2-3 at max.

With yours dropping to 10mpg, my first thought is a bad O2 sensor; when they fail, they enrichen the mixture. If this is your issue, the inside of your tailpipe will likely be black and wet.

One other thought...are you idling the vehicle for long periods to warm it up before driving? That will drive down your mileage.

[ironman2712]

yeap, my tail pipe was totally pitch black and when engine was running water dropped from it constantly, so i replaced the o2 sensor as you advised and averything came back to normal-sth like 18mpg( prapobly those 2mpg i lost due to winter), thanks a lot mate, i would never have figured it out myself, fredjacksonsan- you are the man

[JIMMY92w]

I started to take note of my Miles and gallons and I'm getting 9.8 M/g. I ask my mechanic and he said that that is what those old things get around.
(Mine is a 1989, 4.0L 4x4 manual with 250K. )
I said that is BS and asked what may be contributing to this low gas mileage.

This is what he suggested:
Fuel Leak
TPS
O2 sensor
IAC (clean)
Exhaust holes
Coolant Temp sensor
MAP
Thermostat not working (closed/open loop)
Clean throttle body

[ironman2712]

9.8mpg-that is bad result, i noticed the best result arround september( i managed to get sth like 21mpg), but the man i got the car from was way better-he had that cherro for 17 years and made over that time a kind of a 'service book' with all he noticed and every single part he replaced and modified.from that book i could read that the best result he got was arround 26mpg(yes-hard to believe) during his trip to south africa( i am located in europe), also what i found is proper tire preasure, proper coolant, and soft driving( means use acc add brake pedal) only when nessesery.I was really scary when i got 10mpg but it's all normal now-so the age of the vehicle doe's not matter realy-proper maintenance does,