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The biggest factor in gas mileage is the driver. Typically, those that drive high mileage cars will drive slower without jack-rabbit starts, and are constantly conscious of the affects on their mpg. That's why so many people become frustrated being behind a Prius.
On the other hand, those that drive low mileage big cars, SUVs and trucks often get lower than the EPA estimates due to their heavy foot,
because they enjoy the power and know they are going to have to
pay at the pump anyway.
That's for sure, the driver has so much to do with MPG.
I used to have a Geo Metro.....if I drove very mindful of fuel economy, I would get about 50MPG.
The driver does significantly affect fuel economy, but the vehicle itself can be a huge factor. Here's an example. The data I'm quoting comes from my ScanGauge, which I use to measure "real world" fuel usage and fuel economy in my vehicles. For my example, I will use my 4-cylinder sedan and 6-cylinder "beater" 4WD. Both are well-maintained, properly tuned and use the same regular unleaded gasoline.
Here we go, from a cold weather start (below 15° F.) to full operating temperature. This part ignores the weight, aerodynamics, drag, etc. of either vehicle. At cold start, the 4 cylinder will use 0.75 gallons of fuel per hour (GPH) to idle, dropping to 0.20 GPH when it is at full operating temperature. The 6 cylinder will start out at a whopping 1.75 gph when cold, dropping to 0.45 gph at full operating temperature. So, right off the bat, without driving a foot, the 6-cylinder is using over twice the amount of fuel as the 4-cylinder--no driver input will affect that.
Now, drive either vehicle on my short commute to work (using minimal idling time to warm up and driving both for maximum fuel economy), and the average fuel economy of the 4-cylinder will be between 16-22 mpg for the trip, while the 6-cylinder will only manage 8-10 mpg. Both engines reach operating temperature in about the same period of driving. Both will barely reach operating temperature before I get to work. On this part of my "test," it is the major vehicle characteristics--engine displacement, vehicle weight, tire rolling resistance, mechanical drag, aerodynamic drag, etc.--that are affecting fuel economy. Simply put, the 6-cylinder 4WD gets roughly half the fuel economy of the 4-cylinder sedan, all other factors being equal. Drive either vehicle without regard for fuel economy will diminish the fuel economy of both, but the 4WD will be affected the most by poor driving habits. Drive the same commute in the summer, and the fuel economy of both vehicles will improve by at least 30% for my short commute--the shortened warm-up needed for the engines in summer being the major difference.
Needless to say, I try to avoid using the 4WD for commuting (or for anything else where 4WD is not necessary) and use the 4-cylinder sedan for most of my driving.
Bottom line: to achieve maximum fuel economy, it takes good driving techniques, a vehicle physically capable of getting good fuel economy, and proper maintenance of the vehicle. Lack any one of the three, and fuel economy will suffer. The driver can control driving technique and vehicle maintenance every driving moment, but the physical capability of the vehicle to achieve fuel economy can best be affected by the driver at the time of vehicle acquisition and relatively seldom thereafter.
There's another factor of cold weather that hasn't been mentioned here, tire air pressure. For every ten degree drop of outside air temperature results in roughly two psi drop of air pressure. If the last time you checked your tire pressure the outside temp was 75 and it's now 45, you may have lost at least six psi in your tires.
The driver does significantly affect fuel economy, but the vehicle itself can be a huge factor. Here's an example. The data I'm quoting comes from my ScanGauge, which I use to measure "real world" fuel usage and fuel economy in my vehicles. For my example, I will use my 4-cylinder sedan and 6-cylinder "beater" 4WD. Both are well-maintained, properly tuned and use the same regular unleaded gasoline.
Here we go, from a cold weather start (below 15° F.) to full operating temperature. This part ignores the weight, aerodynamics, drag, etc. of either vehicle. At cold start, the 4 cylinder will use 0.75 gallons of fuel per hour (GPH) to idle, dropping to 0.20 GPH when it is at full operating temperature. The 6 cylinder will start out at a whopping 1.75 gph when cold, dropping to 0.45 gph at full operating temperature. So, right off the bat, without driving a foot, the 6-cylinder is using over twice the amount of fuel as the 4-cylinder--no driver input will affect that.
Now, drive either vehicle on my short commute to work (using minimal idling time to warm up and driving both for maximum fuel economy), and the average fuel economy of the 4-cylinder will be between 16-22 mpg for the trip, while the 6-cylinder will only manage 8-10 mpg. Both engines reach operating temperature in about the same period of driving. Both will barely reach operating temperature before I get to work. On this part of my "test," it is the major vehicle characteristics--engine displacement, vehicle weight, tire rolling resistance, mechanical drag, aerodynamic drag, etc.--that are affecting fuel economy. Simply put, the 6-cylinder 4WD gets roughly half the fuel economy of the 4-cylinder sedan, all other factors being equal. Drive either vehicle without regard for fuel economy will diminish the fuel economy of both, but the 4WD will be affected the most by poor driving habits. Drive the same commute in the summer, and the fuel economy of both vehicles will improve by at least 30% for my short commute--the shortened warm-up needed for the engines in summer being the major difference.
Needless to say, I try to avoid using the 4WD for commuting (or for anything else where 4WD is not necessary) and use the 4-cylinder sedan for most of my driving.
Bottom line: to achieve maximum fuel economy, it takes good driving techniques, a vehicle physically capable of getting good fuel economy, and proper maintenance of the vehicle. Lack any one of the three, and fuel economy will suffer. The driver can control driving technique and vehicle maintenance every driving moment, but the physical capability of the vehicle to achieve fuel economy can best be affected by the driver at the time of vehicle acquisition and relatively seldom thereafter.
Wow, neat information about the amount of gas a vehicle uses at cold startup, I did not know this.
I guess it would make sense to get a block heater to pre-warm the engine on cold days????
Wow, neat information about the amount of gas a vehicle uses at cold startup, I did not know this.
I guess it would make sense to get a block heater to pre-warm the engine on cold days????
In very cold weather, a block heater will help. Unless the temperature is way below zero, though, it doesn't make sense to leave the heater on all night. I use a heavy duty timer on mine that will turn the heater on at around 4 AM. By the time I head for work, it will have the engine warmed up to around 40°-50°. The block heater uses about 20-30 cents of electricity to run for the approximately 3 1/2 hours before I go to work. What a block heater does not help, though, is the temperature of the transmission, differentials, etc. That oil can get pretty thick in low temperatures, the drag of which can lower fuel economy, as well. One other note: "true" block heaters that are usually installed in the freeze plug hole in the engine block are pretty efficient as far as electrical power consumption. "Tank" type heaters that install in the heater hose, however, tend to be very high wattage units that use a lot of power. I don't recommend using tank-type engine heaters, nor do I recommend "dipstick" style engine heaters.
Fuel used at idle is directly related to engine displacement and number of cylinders. The more mass there is to move in the engine and the more friction there is, the more fuel that will be used. Diesel engines will generally use less fuel at idle than gasoline engines of similar size, however, late model emission controls designed to get diesel engines up to temperature quickly and to lower emissions have narrowed that gap considerably, along with the more efficient fuel injection systems used on modern gasoline engines. Also, the new particulate traps and urea injection systems found on most 2011 and up model diesel vehicles are very unfriendly to extended engine idling--and the "regen" cycles on some of those engines necessary to burn the particulates out of the particulate trap use considerable fuel. Any extended idling of those engines increases the number of regens that must run to keep the trap clean.
Finally, as noted by another poster, proper tire pressure is critical to good fuel economy and checking it regularly is important.
In very cold weather, a block heater will help. Unless the temperature is way below zero, though, it doesn't make sense to leave the heater on all night. I use a heavy duty timer on mine that will turn the heater on at around 4 AM. By the time I head for work, it will have the engine warmed up to around 40°-50°. The block heater uses about 20-30 cents of electricity to run for the approximately 3 1/2 hours before I go to work. What a block heater does not help, though, is the temperature of the transmission, differentials, etc. That oil can get pretty thick in low temperatures, the drag of which can lower fuel economy, as well. One other note: "true" block heaters that are usually installed in the freeze plug hole in the engine block are pretty efficient as far as electrical power consumption. "Tank" type heaters that install in the heater hose, however, tend to be very high wattage units that use a lot of power. I don't recommend using tank-type engine heaters, nor do I recommend "dipstick" style engine heaters.
Fuel used at idle is directly related to engine displacement and number of cylinders. The more mass there is to move in the engine and the more friction there is, the more fuel that will be used. Diesel engines will generally use less fuel at idle than gasoline engines of similar size, however, late model emission controls designed to get diesel engines up to temperature quickly and to lower emissions have narrowed that gap considerably, along with the more efficient fuel injection systems used on modern gasoline engines. Also, the new particulate traps and urea injection systems found on most 2011 and up model diesel vehicles are very unfriendly to extended engine idling--and the "regen" cycles on some of those engines necessary to burn the particulates out of the particulate trap use considerable fuel. Any extended idling of those engines increases the number of regens that must run to keep the trap clean.
Finally, as noted by another poster, proper tire pressure is critical to good fuel economy and checking it regularly is important.
Thanks a lot for all of the great information. I am going to look into the block heaters that are powered by the battery. I live in a place that has pretty cold winters....guess I will keep light oil in the vehicle that I soon buy. And yeah, tire pressure is a biggie. Maybe some of that low drag body wax will help too.
Thanks a lot for all of the great information. I am going to look into the block heaters that are powered by the battery. I live in a place that has pretty cold winters....guess I will keep light oil in the vehicle that I soon buy. And yeah, tire pressure is a biggie. Maybe some of that low drag body wax will help too.
Battery-powered block heaters are ineffective. A typical AC block heater is around 450-800 watts--that is about the minimum wattage to be effective to warm an engine in very cold weather. A battery-powered heater can only operate on a very small fraction of that wattage. It can't produce enough BTU's to be effective in cold weather. Remember, you are trying to heat 200-400 lbs. of uninsulated metal from whatever the outside temperature is to around 30°-50° F. No two ways about it, that takes energy.
One final note: a well-maintained gasoline engine with a strong battery should start reliably down to around -20° F. Below that temperature, it gets dicey without a block heater. Diesel engines may start down at that temperature, but the battery and charging system must be in absolutely perfect running order. I generally used the block heater on my diesel vehicles anytime the temperature got below 0 to 10 above. Any lower than -20° F. and a block heater is pretty much an essential for reliable starting of any vehicle. I knew a lot of guys who worked in the oil fields, etc., where electric power for a block heater was not available, that would leave their vehicles idling all night if the temperature was below, say, -10° F. With the current model emission controls on diesel engines, that is now a real problem--extended idling can permanently plug the particulate trap, which costs about $3,000 to replace. Now, some of those guys carry a gasoline-powered AC generator with them to run the block heater, so they can shut the engine off. Another example of unintended negative consequences from overzealous EPA emission regulations on diesel vehicles. Some companies have reluctantly abandoned the more fuel-efficient diesel engines in their pickups and gone back to gas because of the extended idling issue with the new diesel engine emission systems. The sad irony is that those gasoline engines use considerably more fuel to idle (with more emissions) than the diesel engines did. I don't recommend extended idling for any engine unless it is absolutely necessary, but it's bad that the current diesel engines really can't do it without likely expensive damage to the emission systems.
I've lived in some extreme northern climates. Extreme cold certainly DOES effect fuel economy. At least initially. Diesels, for instance, require #1 fuel which is less efficient than #2. That's just one example.
However, after a vehicle is warmed to operating temperature, outside temperature has little to do with fuel economy. That depends on the driver.
My 700watt block heater can take my 1000lb diesel from -24*F to 50*f in 2hr.
Your behind the times when it comes to diesels. The kinks have been ironed out.
New diesels (pick-up trucks) can regenerate the DPF when idling so you no longer need to worried about clogging them up.
Meany older models (that have a DPF) are/can be re-flashed (reprogrammed) to allow a stationary regen.
An espar heater will take care of their situation as it will heat the engine and cab without any outside power.(self contained)
The key to cold weather starting is good batteries and the right oil.
I've started both diesels and gas vehicles in -40*F and colder without any outside aids like plunging it in or starting fluids.
Quote:
Originally Posted by jazzlover
Battery-powered block heaters are ineffective. A typical AC block heater is around 450-800 watts--that is about the minimum wattage to be effective to warm an engine in very cold weather. A battery-powered heater can only operate on a very small fraction of that wattage. It can't produce enough BTU's to be effective in cold weather. Remember, you are trying to heat 200-400 lbs. of uninsulated metal from whatever the outside temperature is to around 30°-50° F. No two ways about it, that takes energy.
One final note: a well-maintained gasoline engine with a strong battery should start reliably down to around -20° F. Below that temperature, it gets dicey without a block heater. Diesel engines may start down at that temperature, but the battery and charging system must be in absolutely perfect running order. I generally used the block heater on my diesel vehicles anytime the temperature got below 0 to 10 above. Any lower than -20° F. and a block heater is pretty much an essential for reliable starting of any vehicle. I knew a lot of guys who worked in the oil fields, etc., where electric power for a block heater was not available, that would leave their vehicles idling all night if the temperature was below, say, -10° F. With the current model emission controls on diesel engines, that is now a real problem--extended idling can permanently plug the particulate trap, which costs about $3,000 to replace. Now, some of those guys carry a gasoline-powered AC generator with them to run the block heater, so they can shut the engine off. Another example of unintended negative consequences from overzealous EPA emission regulations on diesel vehicles. Some companies have reluctantly abandoned the more fuel-efficient diesel engines in their pickups and gone back to gas because of the extended idling issue with the new diesel engine emission systems. The sad irony is that those gasoline engines use considerably more fuel to idle (with more emissions) than the diesel engines did. I don't recommend extended idling for any engine unless it is absolutely necessary, but it's bad that the current diesel engines really can't do it without likely expensive damage to the emission systems.
Meany diesels will warn you about using straight #1.
Winter fuel is a mix of #1  and they use anti-gell additives.
Like I mentioned earler."Most folks see a drop in millage with winter fuel.(regardless of the out side temps as the fuel has less btu's than the summer mix.)( more oxygenates or a mix of fuels, #1 
The outside air temp does play a role in millage even on a engine that is up to operating temp.
Quote:
Originally Posted by JohnBanson
I've lived in some extreme northern climates. Extreme cold certainly DOES effect fuel economy. At least initially. Diesels, for instance, require #1 fuel which is less efficient than #2. That's just one example.
However, after a vehicle is warmed to operating temperature, outside temperature has little to do with fuel economy. That depends on the driver.
My 700watt block heater can take my 1000lb diesel from -24*F to 50*f in 2hr.
Your behind the times when it comes to diesels. The kinks have been ironed out.
New diesels (pick-up trucks) can regenerate the DPF when idling so you no longer need to worried about clogging them up.
Meany older models (that have a DPF) are/can be re-flashed (reprogrammed) to allow a stationary regen.
An espar heater will take care of their situation as it will heat the engine and cab without any outside power.(self contained)
The key to cold weather starting is good batteries and the right oil.
I've started both diesels and gas vehicles in -40*F and colder without any outside aids like plunging it in or starting fluids.
Meany diesels will warn you about using straight #1.
Winter fuel is a mix of #1 and they use anti-gell additives.
Like I mentioned earler."Most folks see a drop in millage with winter fuel.(regardless of the out side temps as the fuel has less btu's than the summer mix.)( more oxygenates or a mix of fuels, #1
The outside air temp does play a role in millage even on a engine that is up to operating temp.
I don't think that you are correct about extended idling not plugging up the particulate filter.
Here is the direct quote from the 2012 Chevy/GMC Duramax diesel operator's manual:
Quote:
Notice: Extended idle should be avoided because the DPF system
is not capable of self cleaning at idle. During extended idle
operation, monitor the instrument panel telltale lights and Driver
Information Center for messages and take appropriate indicated
action. Continued idling with the warning light/message on could
cause irreversible damage to the DPF requiring repair and possible
replacement that might not be covered by the vehicle warranty.
Nothing ambiguous in that warning. "Appropriate action," according to my mechanic who has extensive experience maintaining diesel pickup fleets, either means driving the vehicle around while it regens (for like a half-hour), or having the vehicle equipped with an optional high-idle control that will run the engine up to around 1,200-1,500 rpm (almost half-full throttle) so that the engine can regen in place. Neither is a "fire and forget" solution that does not require operator intervention.
As to starting vehicles without heaters or starting aids at -40°, I, too, have done it--but it is not something I would stake my life or safety on being able to do successfully on a consistent basis.
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