After many decades of experiments the answer is obvious yet it is not what people talk about. The test cars:
Heavy SUVs as the extended versions of the Expedition and Navigator, 6 - 7,000 lbs.
Heavy sedans as a Maybach 57, Flying Spur Speed, a Ghost, 5,500 - 7,000 lbs.
Sporty cars as an Enzo, Murcielago, 2,500 - 3,500 lbs.
Improving fuel economy is particularly important in these cars that may otherwise "suck it up."
Let's go over some of the factors involved. Typical use as an example is the Ford Expedition EL weighing in at about 7,000 lbs. The EPA figures on my last one were 16 and 20 if I remember correctly. Incidently, over the years the EPA numbers improved for the vehicle mostly because they have increased the number of gears in the transmission. My first Expedition had 4 gears and the EPA was something as 11 and 14 MPG. Over the years the SUV moved to 6, 8 and now 10 speed transmissions. With each increase was better EPA milage. Anyway, in no particular order:
Tire Pressure
This is so often overlooked yet plays a major role, easily 1 - 2 MPG. Let’s say the recommended amount is 35 PSI. I always pressurize at least 5 PSI over that which is spec’d. I check monthly and more often when the weather is cooling. My tires never got down to 35 PSI during the interval. Most people set it to 35 PSI and let it get down 5 or even 10 PSI before bringing it back to 35. Tire failures are often related to under inflated tires. I have NEVER seen the “dreaded” central wear pattern of the “over inflated” tire. Not once. Except for the one time when my wheel alignment in the rear was off, all tires have worn evenly.
Proper Wheel Alignment
I have no data on this. For the most part, my tires have worn evenly therefore they were set appropriately for the way I drive. But certainly there would be a penalty with increasing mis-alignment. I cannot give you an estimate but common sense should prevail. In the same department would be proper suspension operation and wheel balancing. Sometimes we recheck this when the tires are about half worn as both my wife and I can feel small differences.
Motor Oil Viscosity
I cannot say that I have noticed a difference going from a 5-30 to a 0-20 grade oil. But maybe as much as a 0.5 MPG increase from using a 40 grade in one step down to a 20 grade oil. Viscosity does make a difference but small. Maybe we should change the oil more often as long term oxidative thickening occurs with motor oils.
I do prefer using thinner oils most of the time. I feel more comfortable revving the engine up sooner running them. And there is definitely more get-up-and-go feeling as the oil is less honey like even at summer Florida temperatures. Who would not like a sportier feeling car? But using thinner oils is not giving me meaningful better fuel economy.
# ONE, Driving Habits
I normally get around 20-21 MPG (around town) the way I drive the SUV. My wife gets a mile or 2 less as she drives as most others. If I try to get the best MPG, I can get as high as 28 - 29 MPG around town. The trouble is that this type of driving annoys the people behind me, you must be careful these days. How is this achieved?
My definition of a good driver is one who rarely uses the brakes. This is done by constantly looking as far ahead as you can, in some cases a mile or so. In areas where you know the pattern of red lights and traffic patterns you can improve on fuel economy by 5 or 10 MPG assuming all else is correct with your vehicle. You anticipate what will happen in front of you. You will maybe slow down a little as you approach a traffic light but rarely stop. Take turns a little faster. Coast as much as possible.
Some cars are limited because they automatically down shift or use regenerative braking when you lift your foot off the gas pedal. If you are the type of driver who does not look ahead and anticipate then maybe this works for you. But if your car coasts well and you can predict what will happen ahead of time coasting is the key. If you brake you are turning kinetic energy into heat, a waste of energy. You have put energy into your car to get it going then you waste it by braking.
Also, though soft starts are of benefit they are not nearly as important as not using the brakes. If you start up faster you get to speed faster then use less gas to maintain your speed sooner. Most of the energy you put in goes to getting you up to speed. But braking is a total waste of energy.
The EPA should concentrate on teaching people how to drive conservatively and take proper care of their vehicles. Here’s another tip. Instead of trying to get to a destination sooner by weaving in and out of traffic, leave earlier!
AEHaas
PS: Next Topic - Coal Burning Cars
Heavy SUVs as the extended versions of the Expedition and Navigator, 6 - 7,000 lbs.
Heavy sedans as a Maybach 57, Flying Spur Speed, a Ghost, 5,500 - 7,000 lbs.
Sporty cars as an Enzo, Murcielago, 2,500 - 3,500 lbs.
Improving fuel economy is particularly important in these cars that may otherwise "suck it up."
Let's go over some of the factors involved. Typical use as an example is the Ford Expedition EL weighing in at about 7,000 lbs. The EPA figures on my last one were 16 and 20 if I remember correctly. Incidently, over the years the EPA numbers improved for the vehicle mostly because they have increased the number of gears in the transmission. My first Expedition had 4 gears and the EPA was something as 11 and 14 MPG. Over the years the SUV moved to 6, 8 and now 10 speed transmissions. With each increase was better EPA milage. Anyway, in no particular order:
Tire Pressure
This is so often overlooked yet plays a major role, easily 1 - 2 MPG. Let’s say the recommended amount is 35 PSI. I always pressurize at least 5 PSI over that which is spec’d. I check monthly and more often when the weather is cooling. My tires never got down to 35 PSI during the interval. Most people set it to 35 PSI and let it get down 5 or even 10 PSI before bringing it back to 35. Tire failures are often related to under inflated tires. I have NEVER seen the “dreaded” central wear pattern of the “over inflated” tire. Not once. Except for the one time when my wheel alignment in the rear was off, all tires have worn evenly.
Proper Wheel Alignment
I have no data on this. For the most part, my tires have worn evenly therefore they were set appropriately for the way I drive. But certainly there would be a penalty with increasing mis-alignment. I cannot give you an estimate but common sense should prevail. In the same department would be proper suspension operation and wheel balancing. Sometimes we recheck this when the tires are about half worn as both my wife and I can feel small differences.
Motor Oil Viscosity
I cannot say that I have noticed a difference going from a 5-30 to a 0-20 grade oil. But maybe as much as a 0.5 MPG increase from using a 40 grade in one step down to a 20 grade oil. Viscosity does make a difference but small. Maybe we should change the oil more often as long term oxidative thickening occurs with motor oils.
I do prefer using thinner oils most of the time. I feel more comfortable revving the engine up sooner running them. And there is definitely more get-up-and-go feeling as the oil is less honey like even at summer Florida temperatures. Who would not like a sportier feeling car? But using thinner oils is not giving me meaningful better fuel economy.
# ONE, Driving Habits
I normally get around 20-21 MPG (around town) the way I drive the SUV. My wife gets a mile or 2 less as she drives as most others. If I try to get the best MPG, I can get as high as 28 - 29 MPG around town. The trouble is that this type of driving annoys the people behind me, you must be careful these days. How is this achieved?
My definition of a good driver is one who rarely uses the brakes. This is done by constantly looking as far ahead as you can, in some cases a mile or so. In areas where you know the pattern of red lights and traffic patterns you can improve on fuel economy by 5 or 10 MPG assuming all else is correct with your vehicle. You anticipate what will happen in front of you. You will maybe slow down a little as you approach a traffic light but rarely stop. Take turns a little faster. Coast as much as possible.
Some cars are limited because they automatically down shift or use regenerative braking when you lift your foot off the gas pedal. If you are the type of driver who does not look ahead and anticipate then maybe this works for you. But if your car coasts well and you can predict what will happen ahead of time coasting is the key. If you brake you are turning kinetic energy into heat, a waste of energy. You have put energy into your car to get it going then you waste it by braking.
Also, though soft starts are of benefit they are not nearly as important as not using the brakes. If you start up faster you get to speed faster then use less gas to maintain your speed sooner. Most of the energy you put in goes to getting you up to speed. But braking is a total waste of energy.
The EPA should concentrate on teaching people how to drive conservatively and take proper care of their vehicles. Here’s another tip. Instead of trying to get to a destination sooner by weaving in and out of traffic, leave earlier!
AEHaas
PS: Next Topic - Coal Burning Cars
