Decrease in fuel "economy" in severe cold
- Thread starter SaabScott
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SaabScott said:
Engines run "better" with cold air as it is more dense. I haven't noticed a sharp drop in mileage (I'm 2WD) the last few days (~0-18 degrees F).
Actually, with the roads slippery and congested which equals slower speeds, my mileage is holding at a 17.3 avg since reset in late November on a long trip (~2800 miles).
Hope its just winter gas and you get it back in the spring. The colder fluids in differentials and Transfer cases could contribute to the drop.
blazinlow89
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BRomanJr said:
Assuming you are using the DIC to monitor fuel mileage, keep in mind those things are less accurate than the weather man. Unless you calculate by hand each tank, you are just getting an average guesttimate.
Most of the causes have been listed, longer warm up times increase fuel consumption, winter blend. Longer idling also contributes to a loss in fuel efficiency, you get exactly 0 mpg when you let the truck idle.
Wooluf1952
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Playsinsnow
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Fuel economy can drop as much as 20% depending on your ambient air temp. Both my cars prove this. Sub zero highway with proper air psi and I got 15.5 mpgs. Thats bad considering I can get 19 mpgs easily with winter gas. Driving like Grandpa. Cold rubber creates more friction too even if psi is same as always. The colder it gets the lower the mpgs. All you can do is not drive or drive more "efficient" to compensate.
I love the way some cars love the cold air and that doesnt help. Tires can lose 1psi for every 10*F difference too, going from a "warm" garage to the freezing cold even when driving because the rubber is that cold.
I love the way some cars love the cold air and that doesnt help. Tires can lose 1psi for every 10*F difference too, going from a "warm" garage to the freezing cold even when driving because the rubber is that cold.
Bartonmd
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BRomanJr said:
More power and increased mileage are not the same. As the air gets colder, engines generally make more power, but get worse mileage. Engines burn a TON more fuel while they're heating up, and the colder it is outside, the longer it takes them to heat up.
Mike
It also takes more power to get it to move all the fluids that are thickened by the cold until warmed up. Tranny, transfer case, diff are stone cold even if you warm up the engine (tranny might pick up a bit of heat from the rad cooler though).
On another note, I had my tranny line blow out on my way to work when it was -30C. It was a rubber line connecting an auxiliary cooler. The extra pressure due to the thick fluid pushed the line off the metal line. I wound up having to fix it right there with two clamps and refilling it. The fluid was like caramel. No wonder.
My mileage has been bad since this cold has been here.
On another note, I had my tranny line blow out on my way to work when it was -30C. It was a rubber line connecting an auxiliary cooler. The extra pressure due to the thick fluid pushed the line off the metal line. I wound up having to fix it right there with two clamps and refilling it. The fluid was like caramel. No wonder.
My mileage has been bad since this cold has been here.
Playsinsnow
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I just got a bump to 20mpgs doing 65mph on a dry road, 24*F. As Mooseman said, fluids and moving parts don't like the cold.
RedEnvoyDenali
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NJTB
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Yes, mine drops from 21-22 to 18-19mpg when the weather gets cold. If I can find a gas station that don't have ethanol it helps a bunch.
IllogicTC
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blazinlow89 said:
While not surprising, it's also kind of disappointing. Considering the computer has control over each injector, and flow rate of each injector should be programmed in already, plus it knows about how much air is coming in to keep stoichiometric ratio, I would have guessed it to be at least as accurate as the weather man. Not expecting precision here (Lord knows if precision was an option they'd tack another $1000 on the list price), but still.
Playsinsnow
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Winter gas is also formulated to vaporize easier in cold weather leaving less energy on combustion than summer gas. I wanted to know why it was cheaper than summer gas and why we couldn't use it all year. The payoff for a warm vehicle is worth it to me.
blazinlow89
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IllogicTC said:
It goes well with our on/off oil pressure switch (and the lying Guage that goes with it), or the always to the right of 210 on the temp guage reading we have.
IllogicTC
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blazinlow89 said:
My temp gauge at least tries a few more ranges of movement besides bottom and middle. I can actually see the increase as it warms up.
The oil gauge is a bunch of hokey-dokey, probably a way to give it a "truck-feel" while not dropping money (and possibly increasing end-consumer MSRP) by using a gauge that reports actual values, rather than the "light-switch" sending unit we have. Personally, knowing that it's not showing the real value, I would have much rather had a much more useful gauge, like an ammeter. Voltmeters can tell a story, but ammeters provide some detail to the story.
Anyone ever notice their temp gauge drop (After reaching full temp) in the winter say when it is 25*F or less and you get on the throttle while on the highway? I noticed mine doing this about a week ago when the temperature was between 10*F to 25*F. As soon as I get off the throttle and the RPMs drop, the gauge moves back to normal operating temp. Just wondering if this is normal or I have/will have an issue soon.
dmanns67 said:
Hmm. It has been cold lately. Single digits. It's hard to make a judgment about this kind of behavior. Mine does this too and I have seen it happen on many cars. And thermostats don't react instantaneously. This could be just due to the cold.
If you are willing to be the guinea pig for this one then by all means. If you see good results I will be the first one changing mine right behind you!
Playsinsnow
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dmanns67 said:
I can get my gauge to bounce by playing with the heat if it's cold enough. I changed my ECT sensor with the thermostat when the code came. The gauge moving is normal behavior in any car I've driven. Just earlier it dropped a few with the heat on in line for a wash. Some folks even restrict the air to the radiator with cardboard to allow it to warm up faster. I did on the wife's old car.
CaptainXL said:
I have driven my TB in the cold before, but either I have never noticed the temp gauge moving or it started last week when I first noticed it. Usually you are not looking at the temp gauge when you are accelerating, but the movement caught the corner of my eye so I started to watch it closely.
The other day I just got home from work and was sitting in my driveway and rev'ed the engine and held at 3500 RPM. I noticed a drop on my temp gauge. Once the RPMs dropped it went back to normal temp.
I did just replace my K&N filter with a green filter from Green Filter USA when I started to notice the gauge movement. Doubt it has anything to do with it, but that was the only thing that changed. At least I am not the only one who has noticed this.
IllogicTC
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My first thought would be normal behavior for a vehicle equipped with an RPM-dependent cooling system. Once the system is warmed up, the fan should be running at a higher percentage of engine speed than if it was cold, so an increase in engine speed would increase fan velocity more. But that's just the first thing to come to mind, assuming no malfunctions of any sort.
If I may derail the subject a moment, blazinlow89 I have a dumb question
On Page 50 of the Gages Service Manual provided in PDF form on here, it describes the system utilizing the standard "measure the resistance to derive the value" system for determining oil pressure. But a look at the pin-outs for the oil pressure sensors shows the 4.2 oil pressure sensor only has Low-Ref and Output Signal, while the 5.3 has Low-Ref, 5V-Ref, and Output Signal. Of course, the system on Page 50 describes it measuring 0-5 volts and deriving the value to display. So does the 5.3 have a true oil sensor? The 4.2's connector diagram calls it a switch, but the 5.3 calls it a sensor.
If I may derail the subject a moment, blazinlow89 I have a dumb question
On Page 50 of the Gages Service Manual provided in PDF form on here, it describes the system utilizing the standard "measure the resistance to derive the value" system for determining oil pressure. But a look at the pin-outs for the oil pressure sensors shows the 4.2 oil pressure sensor only has Low-Ref and Output Signal, while the 5.3 has Low-Ref, 5V-Ref, and Output Signal. Of course, the system on Page 50 describes it measuring 0-5 volts and deriving the value to display. So does the 5.3 have a true oil sensor? The 4.2's connector diagram calls it a switch, but the 5.3 calls it a sensor.
Bartonmd
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IllogicTC said:My first thought would be normal behavior for a vehicle equipped with an RPM-dependent cooling system. Once the system is warmed up, the fan should be running at a higher percentage of engine speed than if it was cold, so an increase in engine speed would increase fan velocity more. But that's just the first thing to come to mind, assuming no malfunctions of any sort.
If I may derail the subject a moment, blazinlow89 I have a dumb question
On Page 50 of the Gages Service Manual provided in PDF form on here, it describes the system utilizing the standard "measure the resistance to derive the value" system for determining oil pressure. But a look at the pin-outs for the oil pressure sensors shows the 4.2 oil pressure sensor only has Low-Ref and Output Signal, while the 5.3 has Low-Ref, 5V-Ref, and Output Signal. Of course, the system on Page 50 describes it measuring 0-5 volts and deriving the value to display. So does the 5.3 have a true oil sensor? The 4.2's connector diagram calls it a switch, but the 5.3 calls it a sensor.
Yes, the 5.3L has a real oil pressure sensor. Likely, because the the gen 3-4 V8 engines have a real sensor in everything else, so it made the controls easier. That reason is purely a guess, though.
The RPM-dependent cooling system has less to do with the fan when it's cold than the vehicle speed (radiator temperature), water pump speed, and thermostat. Also, about all of the newer engines have the thermostat on the incoming coolant side, and not the out. The gen 3-4 small blocks have it in the water pump housing, where it has the part that controls the open/close touching the incoming coolant from the radiator, the hot coolant going to the heater core, and the coolant coming back from the heater core. The gen 3-4 small blocks keep EXCELLENT track of their temperature! The 4200, on the other hand, has the thermostat just sitting in the side of the block, in the water jacket, the water pump in the front of the engine, and the coolant temp sensor on the back of the head. It doesn't keep as close control of the engine temperature at non-steady-state running temperatures (i.e. when the radiator is cold, but the engine is warmed up) as a lot of other engines do, so it's easy to get a variance of a few degrees when the thermostat is opened the right amount for idling, then you all of a sudden turn the coolant flow up, and it takes a bit to react. It also does the opposite in the summer. The I6 engines seem to heat up more than the V8s when you are running down the interstate (high load, lots of airflow), then pull off, stop, and idle.
Having said that, if you're having the temp move more on acceleration than you're expecting (certainly, when it's enough to trip a SES light), it's almost certainly not the sensor, and is almost certainly a thermostat that's getting lazy.
Mike
georgemccarthy
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Hello all. Quick question. I purchased an 09 enclave with 33000 mikes on it. Brought it to a dealership because of a misfiring at about 50 mph. They informed me it wS a bad coil and I also had a leak in rack and pinion steering. First quoted me 2400 and then came down to 2000. This accurate? Thanks!
You might consider this true story from my experience with the above ideas and YOUR recent occurrence:
My wife's Buick LeSabre with the standard engine for them all (V6) had a miss and a code for 2 cylinders and a fix engine light.
Of course the ever dutiful husband who works (me), did not have time to work on it right then, so I took it to the local MAJOR dealer for the Chevy, Buick, etc. here in my town for a QUOTE. They told me they had removed the spark plugs, removed and cleaned the injectors, reset the codes, and that I needed all new injectors, plugs, and some other minor work done to fix it right: Cost $100 for the quote, and around $1800 for all the work that must be done to fix it. (Ever sort feel like YJBS? (you know, "Youv'e Just Been Screwed" type of thing?)
So, I took the car home and opened it up: All of it was lies. None of the plugs had been removed, none of the injectors were sticky or defective and were all untouched by the dealership, and even the O2 sensor was fine. I removed the plugs and the mileage then was about 50K and since it was that high on milage, I also changed out the O2 sensor. All the plugs had been firing evenly but the gaps were about .070" or more. I carefully regapped the plugs to .037", reinstalled them, reset the codes and 4 years later when we sold that 2007 Buick with 78K milkes on it, it was still running excellently.
The over gapped (worn) plugs had caused an occassional misfire which coded and turned on the fix engine light. No injectors, or new wires**, nor new plugs, and add one new O2 sensor - nothing but a tad bit of self-effort fixed it this time and cost nearly zero. They had used the "computer readout" at the dealer on their factory equipment to "prognosticate" on the probably causes and recommended fixes.
So I encourage you to check out the basics first on your own if you are capable. If you cannot do that, then call friends and also BBB in your area to find shops that operate for years without customer complaints. All my best to you buddy, Gary
** IF you are not VERRY careful as you remove the plug wires you will have to replace them all! The carbon cores become brittle over time, and "set up" in their exact shape and form, then when removed (disturbed) the carbon is cracked internally and often plug wire falures result in misfires over time. Move as gently and minimally as possible always. gli
My wife's Buick LeSabre with the standard engine for them all (V6) had a miss and a code for 2 cylinders and a fix engine light.
Of course the ever dutiful husband who works (me), did not have time to work on it right then, so I took it to the local MAJOR dealer for the Chevy, Buick, etc. here in my town for a QUOTE. They told me they had removed the spark plugs, removed and cleaned the injectors, reset the codes, and that I needed all new injectors, plugs, and some other minor work done to fix it right: Cost $100 for the quote, and around $1800 for all the work that must be done to fix it. (Ever sort feel like YJBS? (you know, "Youv'e Just Been Screwed" type of thing?)
So, I took the car home and opened it up: All of it was lies. None of the plugs had been removed, none of the injectors were sticky or defective and were all untouched by the dealership, and even the O2 sensor was fine. I removed the plugs and the mileage then was about 50K and since it was that high on milage, I also changed out the O2 sensor. All the plugs had been firing evenly but the gaps were about .070" or more. I carefully regapped the plugs to .037", reinstalled them, reset the codes and 4 years later when we sold that 2007 Buick with 78K milkes on it, it was still running excellently.
The over gapped (worn) plugs had caused an occassional misfire which coded and turned on the fix engine light. No injectors, or new wires**, nor new plugs, and add one new O2 sensor - nothing but a tad bit of self-effort fixed it this time and cost nearly zero. They had used the "computer readout" at the dealer on their factory equipment to "prognosticate" on the probably causes and recommended fixes.
So I encourage you to check out the basics first on your own if you are capable. If you cannot do that, then call friends and also BBB in your area to find shops that operate for years without customer complaints. All my best to you buddy, Gary
** IF you are not VERRY careful as you remove the plug wires you will have to replace them all! The carbon cores become brittle over time, and "set up" in their exact shape and form, then when removed (disturbed) the carbon is cracked internally and often plug wire falures result in misfires over time. Move as gently and minimally as possible always. gli