Improved fuel economy saves you money every time you fill up!
A vehicle that gets 30 MPG will cost you $880 less to fuel each year than one that gets 20 MPG (assuming 15,000 miles of driving annually and a fuel cost of $3.52).
Over a period of 5 years, the 30-MPG vehicle will save you $4,400.
Alternative Fuels
There are several alternatives to using plain old petrol or diesel in our cars. Some of these alternate fuels require some modifications to your car, whilst others are only available by buying a new car, such as the Toyota Prius.
On the next few pages we'll look at a few of the more viable alternatives that are available on the market right now. There are quite a few pie-in-they-sky ideas that people are coming up with, like engines running on compressed air or modern steam turbines ... we'll give those a miss for now as, although they may be great ideas, we cant see them taking off anytime soon, but if they do we'll update the site!
Hybrid Cars
Hybrid cars are probably one of the most well-known alternative fuels for cars at the moment, with the Toyota Prius probably being the archetypal car that most people are familiar with.
Hybrid cars usually make use of a normal (albeit fairly small capacity) petrol engine coupled with an electric motor and a suitable electrical system (i.e. a computer to control the system, batteries and so on). The on-board computer decides when to use the engine, the electric motor, or a combination of the two to get the best efficiency. For example, a hybrid may use the efficient electric motor to get the car moving initially, and then switch over to the engine when more performance is required.
Through this cunning use of electric motors in combination with the traditional engine, hybrid cars can get great fuel economy whilst driving around town in busy stop-start traffic. However, some have questioned their ability for out of town driving where the official fuel consumption figure of 67.3 is in the same region as many of today's small diesel super-minis, which are significantly cheaper to purchase. Interestingly, the manufacturers have yet to release a hybrid diesel super-mini!
Biodiesel
Biodiesel is essentially the same as diesel, except it is produced from plant sources such as rapeseed oil instead of crude oil. It is important to note that Biodiesel is perfectly legal in the UK, and it is not related to the stories we often hear about people pouring the waste oil from their local Chippie straight into their fuel tanks!
Biodiesel can be used in most modern diesels without any modifications, and can be mixed with regular diesel in any ratio to produce various "blends". However, biodiesel has been known to damage natural rubber which may be used in fuel lines and other engine components on older (usually before 1995) cars.
You may be wondering, if its so similar to regular diesel, why am I talking about it in the context of alternative fuels? Well one reason is that biodiesel is carbon-neutral, but the main reason is biodiesel can actually be made by yourself from waste oils! There are a lot of companies that are selling kits and instructions that will allow you produce your own from your shed or garage. Its important to note though that you'll still be liable to pay some fuel tax if you produce it yourself, but this is only at about 27pence a litre - significantly less than regular diesel.
If you aren't up to making your own biodiesel, that offer a regularly updated list of places where you can buy premade biodiesel.
Units of measure
MPG to L/100km conversion chart: blue: U.S. gal, red: imp gal (UK)The two most common ways to measure automobile fuel usage are:
Fuel consumption
The amount of fuel used per distance; Often an arbitrary distance, most commonly litres per 100 kilometres (L/100 km). This measure is used in Europe, China, Canada, Australia and New Zealand.
Fuel economy (efficiency)
Efficiency is defined as output per input. In automobiles it is the distance traveled per unit of fuel used; in miles per gallon (mpg) or kilometres per litre (km/L), commonly used in in the UK, U.S. (mpg) and Japan, Korea, India, Pakistan, parts of Africa, The Netherlands, Denmark and Latin America (km/L). If mpg is used, it is important to know which gallon is being referred to; the imperial gallon is about 20% larger than the U.S. gallon.
Fuel economy and fuel consumption are reciprocal quantities. To convert either way between L/100 km and miles per U.S. gallon, divide 235 by the number in question; for miles per imperial gallon, divide 282 by either number. For example, to convert from 30 mpg (U.S.) to L/100 km, divide 235 by 30, giving 7.83 L/100 km; or from 10 L/100 km to mpg (U.S.), divide 235 by 10, giving 23.5 mpg. To convert between L/100 km and km/L, divide 100 by the number in question.
A related measure is the amount of carbon dioxide produced as a result of the combustion process, typically measured in grams of CO2 per kilometre (CO2 g/km). A petrol (gasoline) engine will produce around 2.32 kg of carbon dioxide for each litre of petrol consumed (19.4 lb/gal). A typical diesel engine produces 2.66 kg/L (22.23 lb/gal) though typically burns fewer litres per kilometre for an otherwise identical car. Since the CO2 emissions are relatively constant per litre, they are proportional to fuel consumption.
Inverse or reciprocal scaleA modest improvement in fuel economy for a relatively inefficient vehicle can provide greater savings in terms of financial cost to the driver and environmental impact than a proportionately larger increase for a more economical vehicle. This is most intuitively demonstrated using the inverse scale — gallons per mile or liters per kilometer. If a driver who travels 15,000 miles (24,000 km) a year switches from a vehicle with 10 mpg to 12 mpg average fuel economy (0.10 gallons per mile to 0.083 gallons per mile), 250 gallons are saved. A similar 20% improvement in exchanging a 30 mpg for a 36 mpg (0.033 gallons per mile for 0.027) vehicle saves only 83 gallons. Because mpg and fuel consumption are inversely related, both can be misinterpreted.[5] Gallons Per Mile is more useful than MPG when comparing the fuel consumption of different cars, while MPG is more useful when comparing the fuel efficiency of different cars.
One should note that MPG works differently from litres per hundred kilometres. l/100 km denotes a rate of fuel consumption, while MPG is a measure of fuel economy (or 'gas mileage'). If a car uses less fuel, the MPG increases, and l/100 km decreases, but the improvement percentages will not equate, because the values are reciprocal.
For example, 20% lower l/100 km does not mean 20%, but 25% more distance. This comes from the following calculation: 20% is 0.8 times less fuel, therefore 100% / 0.8 = 125% of the original distance, or 25% further on every litre.
Because consumption is an inverse function of MPG, MPG can be misinterpreted in terms of fuel consumption improvement. Some people intuitively take the difference in MPG when comparing two cars. This leads them to underestimate the savings from small improvements on low MPG cars (e.g., 14 to 20 MPG, which saves twice as much fuel over a given distance as the improvement from 33 to 50 MPG[6]). A measure of gallons per mile (GPM), such as gallons per 100 miles, provides a one-for-one comparison of the consumption for a given distance of driving. Unlike MPG, the GPM of one car can be subtracted from the GPM of another car to get a direct measure of fuel savings. Inversely this becomes a moot point to the driver who wishes to get the most traveling out of a tank of fuel. Here the MPG values give a clear measure of "bang for your buck" and are directly comparable; an improvement of 20% MPG means 20% more traveling for any car. In this case comparing the difference in GPM values would be misleading. (e.g. an improvement from 0.2 to 0.1 GPM gets the driver twice as far on a tank, but an improvement of 0.3 to 0.2 GPM only gets the driver 50% further.) Since many people do not know how far they will drive, but know how large their fuel tank is, the MPG value remains more useful to them.
Gallons per mileGallons per mile (GPM) is a way of measuring the fuel consumption of a vehicle. It conveys the amount of fuel that will be used more intuitively than Miles per gallon, which can be misleading. For example, many people incorrectly believe that the improvement from 34 to 44 mpg-US (6.9 to 5.3 L/100 km) saves more fuel than the improvement from 15 to 19 mpg-US (16 to 12 L/100 km) because they look at the difference (or percentage change) between MPG levels. The improvement of 15 to 19 mpg change saves about twice as much fuel as the improvement of 34 to 44 mpg over a given distance of driving. "Gallons per 100 miles" (GPHM) corrects these illusions. When comparing the fuel savings of different vehicles, GPHM can be subtracted. MPG cannot.
Because using "gallons per mile" yields small numbers, it is useful to use a longer distance as the base, such as "gallons per hundred miles" (GPHM) or "gallons per 10,000 miles. Many countries use a measure of volume over distance to measure fuel consumption.
The following table shows how MPG translates to "gallons per 100 miles" (GPHM) and gallons per 10,000 miles (GP10K), with small rounding:
A focus on fuel consumption makes clear the benefits of removing the most inefficient vehicles, as in the Car Allowance Rebate System program. Seemingly small MPG improvements on inefficient cars saves a large amount of fuel over a given distance of driving. For example, replacing a car that gets 14 mpg-US (17 L/100 km) with a car that gets 25 mpg-US (9.4 L/100 km) MPG saves 3 US gallons (11 L) of fuel every 100 miles (160 km). Because 1 US gallon (3.8 L) of fuel emits 20 pounds (9.1 kg) of carbon dioxide,[9] saving 3 US gallons (11 L) of fuel every 100 miles (160 km) saves 3 short tons (2.7 t) of carbon dioxide every 10,000 miles (16,000 km) of driving.
Fuel economy statisticsWhile the ability of petroleum engines to maximize the transformed chemical energy of the fuel (their fuel efficiency) has increased since the beginning of the automotive era, this has not necessarily translated into increased fuel economy or decreased fuel consumption, which is additionally affected by the mass, shape, and size of the car, and the goals of an automobile's designers, which may be to produce greater power and speed rather than greater economy and range.
Fuel economy data reliabilityThe mandatory publication of the fuel consumption by the manufacturer led some to use dubious practices to reach better values in the past. If the test is on a test stand, the vehicle may detect open doors and adapt the engine control. Also when driven according to the test regime, the parameters may adapt automatically. Test laboratories use a "golden car" that is tested in each one to check that each lab produces the same set of measurements for a given drive cycle.
Correctly aligning the vehicle wheels is something that should be normal practice for the vehicle users. Tire pressures and lubricants have to be as recommended by the manufacturer (Higher tire pressures are required on a particular dyno type, but this is to compensate for the different rolling resistance of the dyno, not to produce an unrealistic load on the vehicle). Normally the quoted figures a manufacturer publishes have to be proved by the relevant authority witnessing vehicle/engine tests. A lot of Governments independently test emissions from customer vehicles, and as a final measure can force a recall of all of a particular type of vehicle if the customer vehicles do not fulfil manufacturers' claims within reasonable limits. The expense and bad publicity from such a recall means manufacturers should be very cautious not to publish unrealistic figures. The U.S. Federal government retests 10-15% of models), to make sure that the
The choice of car and how it is driven drastically affects the fuel economy. A top fuel dragster can consume 6 U.S. gallons (23 L) of nitromethane for a quarter-mile (400 m) run in about 4.5 seconds, which comes out to 24 U.S. gallons per mile (5,600 L per 100 km). The other extreme was set by PAC-Car II in the 2005 Eco-Marathon, which managed 5384 kilometres per litre (15,210 mpg-imp; 12,660 mpg-US).
Both such vehicles are extremes, and most people drive ordinary cars that typically average 15 to 40 miles per U.S. gallon (19 to 50 miles per imperial gallon) or (5.6 to 15 L per 100 km). However, due to environmental concerns caused by CO2 emissions, new EU regulations are being introduced to reduce the average emissions of cars sold beginning in 2012, to 130 g/km of CO2, equivalent to 4.5 L per 100 km (52 mpg U.S., 63 MPG imperial) for a diesel-fueled car, and 5.0 L per 100 km (47 mpg U.S., 56 MPG imperial) for a gasoline (petrol)-fueled car.]
It should be borne in mind that the average consumption across the fleet is not immediately directly affected by the new vehicle fuel economy, for example Australia's car fleet average in 2004 was 11.5 L/100 km (20.5 mpgU.S.), compared with the average new car consumption in the same year of 25.3 mpgU.S
A vehicle that gets 30 MPG will cost you $880 less to fuel each year than one that gets 20 MPG (assuming 15,000 miles of driving annually and a fuel cost of $3.52).
Over a period of 5 years, the 30-MPG vehicle will save you $4,400.
Alternative Fuels
There are several alternatives to using plain old petrol or diesel in our cars. Some of these alternate fuels require some modifications to your car, whilst others are only available by buying a new car, such as the Toyota Prius.
On the next few pages we'll look at a few of the more viable alternatives that are available on the market right now. There are quite a few pie-in-they-sky ideas that people are coming up with, like engines running on compressed air or modern steam turbines ... we'll give those a miss for now as, although they may be great ideas, we cant see them taking off anytime soon, but if they do we'll update the site!
Hybrid Cars
Hybrid cars are probably one of the most well-known alternative fuels for cars at the moment, with the Toyota Prius probably being the archetypal car that most people are familiar with.
Hybrid cars usually make use of a normal (albeit fairly small capacity) petrol engine coupled with an electric motor and a suitable electrical system (i.e. a computer to control the system, batteries and so on). The on-board computer decides when to use the engine, the electric motor, or a combination of the two to get the best efficiency. For example, a hybrid may use the efficient electric motor to get the car moving initially, and then switch over to the engine when more performance is required.
Through this cunning use of electric motors in combination with the traditional engine, hybrid cars can get great fuel economy whilst driving around town in busy stop-start traffic. However, some have questioned their ability for out of town driving where the official fuel consumption figure of 67.3 is in the same region as many of today's small diesel super-minis, which are significantly cheaper to purchase. Interestingly, the manufacturers have yet to release a hybrid diesel super-mini!
Biodiesel
Biodiesel is essentially the same as diesel, except it is produced from plant sources such as rapeseed oil instead of crude oil. It is important to note that Biodiesel is perfectly legal in the UK, and it is not related to the stories we often hear about people pouring the waste oil from their local Chippie straight into their fuel tanks!
Biodiesel can be used in most modern diesels without any modifications, and can be mixed with regular diesel in any ratio to produce various "blends". However, biodiesel has been known to damage natural rubber which may be used in fuel lines and other engine components on older (usually before 1995) cars.
You may be wondering, if its so similar to regular diesel, why am I talking about it in the context of alternative fuels? Well one reason is that biodiesel is carbon-neutral, but the main reason is biodiesel can actually be made by yourself from waste oils! There are a lot of companies that are selling kits and instructions that will allow you produce your own from your shed or garage. Its important to note though that you'll still be liable to pay some fuel tax if you produce it yourself, but this is only at about 27pence a litre - significantly less than regular diesel.
If you aren't up to making your own biodiesel, that offer a regularly updated list of places where you can buy premade biodiesel.
Units of measure
MPG to L/100km conversion chart: blue: U.S. gal, red: imp gal (UK)The two most common ways to measure automobile fuel usage are:
Fuel consumption
The amount of fuel used per distance; Often an arbitrary distance, most commonly litres per 100 kilometres (L/100 km). This measure is used in Europe, China, Canada, Australia and New Zealand.
Fuel economy (efficiency)
Efficiency is defined as output per input. In automobiles it is the distance traveled per unit of fuel used; in miles per gallon (mpg) or kilometres per litre (km/L), commonly used in in the UK, U.S. (mpg) and Japan, Korea, India, Pakistan, parts of Africa, The Netherlands, Denmark and Latin America (km/L). If mpg is used, it is important to know which gallon is being referred to; the imperial gallon is about 20% larger than the U.S. gallon.
Fuel economy and fuel consumption are reciprocal quantities. To convert either way between L/100 km and miles per U.S. gallon, divide 235 by the number in question; for miles per imperial gallon, divide 282 by either number. For example, to convert from 30 mpg (U.S.) to L/100 km, divide 235 by 30, giving 7.83 L/100 km; or from 10 L/100 km to mpg (U.S.), divide 235 by 10, giving 23.5 mpg. To convert between L/100 km and km/L, divide 100 by the number in question.
A related measure is the amount of carbon dioxide produced as a result of the combustion process, typically measured in grams of CO2 per kilometre (CO2 g/km). A petrol (gasoline) engine will produce around 2.32 kg of carbon dioxide for each litre of petrol consumed (19.4 lb/gal). A typical diesel engine produces 2.66 kg/L (22.23 lb/gal) though typically burns fewer litres per kilometre for an otherwise identical car. Since the CO2 emissions are relatively constant per litre, they are proportional to fuel consumption.
Inverse or reciprocal scaleA modest improvement in fuel economy for a relatively inefficient vehicle can provide greater savings in terms of financial cost to the driver and environmental impact than a proportionately larger increase for a more economical vehicle. This is most intuitively demonstrated using the inverse scale — gallons per mile or liters per kilometer. If a driver who travels 15,000 miles (24,000 km) a year switches from a vehicle with 10 mpg to 12 mpg average fuel economy (0.10 gallons per mile to 0.083 gallons per mile), 250 gallons are saved. A similar 20% improvement in exchanging a 30 mpg for a 36 mpg (0.033 gallons per mile for 0.027) vehicle saves only 83 gallons. Because mpg and fuel consumption are inversely related, both can be misinterpreted.[5] Gallons Per Mile is more useful than MPG when comparing the fuel consumption of different cars, while MPG is more useful when comparing the fuel efficiency of different cars.
One should note that MPG works differently from litres per hundred kilometres. l/100 km denotes a rate of fuel consumption, while MPG is a measure of fuel economy (or 'gas mileage'). If a car uses less fuel, the MPG increases, and l/100 km decreases, but the improvement percentages will not equate, because the values are reciprocal.
For example, 20% lower l/100 km does not mean 20%, but 25% more distance. This comes from the following calculation: 20% is 0.8 times less fuel, therefore 100% / 0.8 = 125% of the original distance, or 25% further on every litre.
Because consumption is an inverse function of MPG, MPG can be misinterpreted in terms of fuel consumption improvement. Some people intuitively take the difference in MPG when comparing two cars. This leads them to underestimate the savings from small improvements on low MPG cars (e.g., 14 to 20 MPG, which saves twice as much fuel over a given distance as the improvement from 33 to 50 MPG[6]). A measure of gallons per mile (GPM), such as gallons per 100 miles, provides a one-for-one comparison of the consumption for a given distance of driving. Unlike MPG, the GPM of one car can be subtracted from the GPM of another car to get a direct measure of fuel savings. Inversely this becomes a moot point to the driver who wishes to get the most traveling out of a tank of fuel. Here the MPG values give a clear measure of "bang for your buck" and are directly comparable; an improvement of 20% MPG means 20% more traveling for any car. In this case comparing the difference in GPM values would be misleading. (e.g. an improvement from 0.2 to 0.1 GPM gets the driver twice as far on a tank, but an improvement of 0.3 to 0.2 GPM only gets the driver 50% further.) Since many people do not know how far they will drive, but know how large their fuel tank is, the MPG value remains more useful to them.
Gallons per mileGallons per mile (GPM) is a way of measuring the fuel consumption of a vehicle. It conveys the amount of fuel that will be used more intuitively than Miles per gallon, which can be misleading. For example, many people incorrectly believe that the improvement from 34 to 44 mpg-US (6.9 to 5.3 L/100 km) saves more fuel than the improvement from 15 to 19 mpg-US (16 to 12 L/100 km) because they look at the difference (or percentage change) between MPG levels. The improvement of 15 to 19 mpg change saves about twice as much fuel as the improvement of 34 to 44 mpg over a given distance of driving. "Gallons per 100 miles" (GPHM) corrects these illusions. When comparing the fuel savings of different vehicles, GPHM can be subtracted. MPG cannot.
Because using "gallons per mile" yields small numbers, it is useful to use a longer distance as the base, such as "gallons per hundred miles" (GPHM) or "gallons per 10,000 miles. Many countries use a measure of volume over distance to measure fuel consumption.
The following table shows how MPG translates to "gallons per 100 miles" (GPHM) and gallons per 10,000 miles (GP10K), with small rounding:
A focus on fuel consumption makes clear the benefits of removing the most inefficient vehicles, as in the Car Allowance Rebate System program. Seemingly small MPG improvements on inefficient cars saves a large amount of fuel over a given distance of driving. For example, replacing a car that gets 14 mpg-US (17 L/100 km) with a car that gets 25 mpg-US (9.4 L/100 km) MPG saves 3 US gallons (11 L) of fuel every 100 miles (160 km). Because 1 US gallon (3.8 L) of fuel emits 20 pounds (9.1 kg) of carbon dioxide,[9] saving 3 US gallons (11 L) of fuel every 100 miles (160 km) saves 3 short tons (2.7 t) of carbon dioxide every 10,000 miles (16,000 km) of driving.
Fuel economy statisticsWhile the ability of petroleum engines to maximize the transformed chemical energy of the fuel (their fuel efficiency) has increased since the beginning of the automotive era, this has not necessarily translated into increased fuel economy or decreased fuel consumption, which is additionally affected by the mass, shape, and size of the car, and the goals of an automobile's designers, which may be to produce greater power and speed rather than greater economy and range.
Fuel economy data reliabilityThe mandatory publication of the fuel consumption by the manufacturer led some to use dubious practices to reach better values in the past. If the test is on a test stand, the vehicle may detect open doors and adapt the engine control. Also when driven according to the test regime, the parameters may adapt automatically. Test laboratories use a "golden car" that is tested in each one to check that each lab produces the same set of measurements for a given drive cycle.
Correctly aligning the vehicle wheels is something that should be normal practice for the vehicle users. Tire pressures and lubricants have to be as recommended by the manufacturer (Higher tire pressures are required on a particular dyno type, but this is to compensate for the different rolling resistance of the dyno, not to produce an unrealistic load on the vehicle). Normally the quoted figures a manufacturer publishes have to be proved by the relevant authority witnessing vehicle/engine tests. A lot of Governments independently test emissions from customer vehicles, and as a final measure can force a recall of all of a particular type of vehicle if the customer vehicles do not fulfil manufacturers' claims within reasonable limits. The expense and bad publicity from such a recall means manufacturers should be very cautious not to publish unrealistic figures. The U.S. Federal government retests 10-15% of models), to make sure that the
The choice of car and how it is driven drastically affects the fuel economy. A top fuel dragster can consume 6 U.S. gallons (23 L) of nitromethane for a quarter-mile (400 m) run in about 4.5 seconds, which comes out to 24 U.S. gallons per mile (5,600 L per 100 km). The other extreme was set by PAC-Car II in the 2005 Eco-Marathon, which managed 5384 kilometres per litre (15,210 mpg-imp; 12,660 mpg-US).
Both such vehicles are extremes, and most people drive ordinary cars that typically average 15 to 40 miles per U.S. gallon (19 to 50 miles per imperial gallon) or (5.6 to 15 L per 100 km). However, due to environmental concerns caused by CO2 emissions, new EU regulations are being introduced to reduce the average emissions of cars sold beginning in 2012, to 130 g/km of CO2, equivalent to 4.5 L per 100 km (52 mpg U.S., 63 MPG imperial) for a diesel-fueled car, and 5.0 L per 100 km (47 mpg U.S., 56 MPG imperial) for a gasoline (petrol)-fueled car.]
It should be borne in mind that the average consumption across the fleet is not immediately directly affected by the new vehicle fuel economy, for example Australia's car fleet average in 2004 was 11.5 L/100 km (20.5 mpgU.S.), compared with the average new car consumption in the same year of 25.3 mpgU.S
