Fuel Mileage

For the best fuel mileage from your car or truck, proper maintenance is the main factor . I have found that when a vehicle performs the best it also gets the best fuel mileage . When any engine is running at its optimum efficiency it will get the most power and the best performance , out of the fuel it is burning . Therefore it requires less fuel to do the same work . An example of this is , if an engine that is running poorly requires that you push the accelerator ½ way to go 60 MPH (100 KMH) but the same engine running at maximum efficiency only requires that you push the accelerator 1/3 , to do the same speed , you see why the efficient engine will use less fuel to go the same distance .

- Engine Oil . Engineers design the engines internal clearances , to use specified viscosity oils (5w30 , 10w30,15w40). You must use the viscosity of oil that your engine is designed to use . Use of to thin an oil can cause premature wear and premature failure in the engine . Use of oil that is to thick may not lubricate the engine properly (specially when cold ) which may cause premature engine parts failures . Oil that is too thick can also cause higher resistance in the engine , which will cause the engine to consume slightly more fuel and get less fuel mileage . Overfilling the engine , by a large amount will also cause higher resistance in the engine which can lower fuel mileage greatly . Clean oil can contribute to better fuel mileage as it lubricates the engine better than old oil . So use the right oil , keep the oil clean and do not overfill the engine , with oil .

- Air filter . A dirty air filter will restrict the air flow into the engine , which will lower the performance and the fuel mileage . The engine requires sufficient clean air to attain a fuel air mixture ratio of about 14 parts air to one part fuel , for the engine to operate at maximum efficiency . A restricted air filter can cause the air in that mixture to drop below that requirement and result in poorer fuel mileage . Check the air filter on every lubrication service and replace it when needed. You will likely find that replacement intervals will be consistently the same . For example , every second , every third or every fourth lubrication service , depending on were you drive (highway or city , dirt roads or paved roads) . If you do a lot of city driving or dirt road driving , more frequent air filter replacement will be required . If you do mostly paved highway driving , the air filter replacement will be less often and at longer mileage distances .

- Tires . Under inflated tires will cause more road resistance against moving the vehicle , and requiring more energy to move the vehicle . This will result in lower fuel mileage , (as much as 20 % - 25 % lower). Due to the sever temperature changes of the tires from driving and sitting , it is normal for tires to gradually loose air pressure .

Most cars should require air pressure of 32 PSI to 35 PSI . Most light trucks require air pressure of 35 PSI to 80 PSI depending on the tire capacity and the weight carried by the vehicle . Statistics show that well over half the vehicles on the road today have under inflated tires. Tire pressure should be checked once a month for best safety and performance as well as best fuel mileage .

- Fuel filter . A restricted fuel filter can cause a lack of power and poor performance as well as lowers fuel mileages . The fuel filter on a vehicle should be replaced at regular intervals . Often 50,000 miles or so (80,000 km) is recommended . If the fuel filter is left too long it can get plugged with dirt etc and cause the performance of the engine to be poor . Poor performance means poor fuel mileage .

- Ignition timing . On most new vehicles , the ignition timing is not adjustable . On those that have adjustable timing , if it is not set right , the mileage will be lower and the performance will also be lacking . Ignition timing is normally checked and adjusted on a tune-up service when needed .

- Spark plugs . As spark plugs get older they get less efficient and do not provide sufficient spark to ignite the fuel mixture as well . This will lower the engine efficiency and cause the engine to burn more fuel . The wrong spark plugs or poor quality spark plugs can also cause the engine to perform with less efficiency , which will cause the engine to consume more fuel .

- Some times cheaper parts are not really such a good deal and can cost more in the long term.

- Spark plug wires . On higher mileage vehicles , defective spark plug wires can cause the engine to run less efficiently , which will lower engine performance and also lower fuel mileage . As the spark plug wire get older the resistance gets greater , causing the ignition of the fuel in the cylinders be poorer . This will lower the engines performance and causes more fuel to be consumed by the engine .

- Spark plug wires are normal tested when the spark plugs are replaced on a tune up service .

- Throttle body . The throttle body controls the air that is taken into the engine .Over a period of time very fine dust will mix with normal fuel vapor residue and crankcase vapors and will form a gum like residue , which will stick to the throttle body and to the throttle plate . This gum etc can cause inaccurate sensor back-feed readings to be given to the Power-train Control Module (PCM) . If the PCM gets false information from any fuel relater sensor , the PCM will always go to richer fuel mixture strategy , to protect the engine against excess cylinder heat . This will cause the engine to burn more fuel , and will lower engine performance too .

The throttle body should be cleaned if needed , when an engine tune up is done .

- Fuel injectors .After a period of driving , fuel injectors can become less efficient due to normal , residue from the additives in the fuel that passes through them . This residue when it builds up can restrict free fuel flow through the injector and also can cause injectors to get sticky . If the injector do not feed enough fuel , then the exhaust oxygen sensor will tell the PCM the fuel mixture is to lean . The PCM will open the fuel injectors further , to compensate , and the engine will burn more fuel .

- Fuels do have additives to help clean the injectors but over time this residue will still accumulate . Fuel injector cleaner additives added to the fuel from time will help to battle this condition .

- A fuel injector flush service will clean the injectors completely

- Failed engine control components or sensors will lower fuel mileage . This is normally accompanied with a noticeable drivability concern , such as lack of power , engine miss, surging , hesitation etc and is often accompanied by a check engine warning light on .

- If a sensor fails to supply information to the Power-train Control Module , The PCM will go to a built in strategy to compensate for the lack of data from that sensor . This strategy can include a rich fuel mode to protect the engine against excessive cylinder temperature . Rich fuel mode will cause the engine to consume more fuel .

- An engine electronic diagnostic test will find the inoperative sensor or part . Replacement of to failed part will cure this condition .

- Improper operating temperature . If an engine is operating at to low a temperature the fuel will not vaporize properly causing less efficient performance and poor fuel mileage . The cause of this is normally that the thermostat is staying open . Replacement of the thermostat and gasket will normally remedy this condition .

If the engine runs too hot it will also be less efficient and harder on fuel . Running too hot can also cause sever engine damage . Low coolant , leaks , restricted radiator , loose belt or malfunctioning water pump are the most common causes of this condition . Regular maintenance will usually prevent this condition from occurring .

- Air intake system . The engines air intake system normally consists of an air duct from outside air to the air cleaner (filter housing), the air cleaner and an air hose from the air cleaner to the throttle body . Some models may also have a mass air flow sensor . If there is any air leak is present in this system it can lower the performance and the fuel mileage greatly . The reason you want cooler outside air fed into the engine is because of the higher density . The hot air from under the hood is much thinner than the outside air . Cooler thick air will expand more than warm thin air , in the cylinders , while using the same fuel . This means that you will need less are to go any give speed or distance . You don’t need to push the accelerator as far to go any speed so you therefore use less fuel . (Are you confused yet ) believe it , cool outside air gives much better fuel mileage . Be sure that system is properly sealed and free of any restrictions .

- Transmission . An automatic transmission that slips (normally on very high mileage vehicles) will cause very poor fuel mileage . Transmission slippage will allow the engine to turn faster that normal , which will consume more fuel . Slipping transmissions don’t live very long , if they are not repaired .

Also if the transmission does not shift properly it can lower fuel mileage . City driving mileage would be affected the most in this case . If the shift points are too high , the engine will turn faster for longer periods of time and burning more fuel . If the shift points are too low , the engine will lug . The vehicle then takes longer to get up to speed and burns more fuel to get up to speed .

Proper maintenance of the transmission will save you money on fuel mileage.

- Alignment . If the steering is not in proper alignment it can cause higher than normal road resistance to move the vehicle , due to tire scuff . This is normally accompanied by non normal tire wear and poor handling . An alignment will cure this condition . This is another reason why alignment should checked from time to time .

- Sticking brakes will cause more resistance for the vehicle to move and the engine will have to work harder and therefore will burn more fuel .

Driving with your foot oh the brake petal will have the same affect and fuel mileage will be lower .

- Bad driving habits. Can be a very large contributor to poor fuel mileage .

Very high speed driving will consume much more fuel than normal . When vehicle is driven within the cruising range of the engine it will get the very best fuel mileage . When a vehicle is driven above cruising range , the higher the speed the worse the mileage will get . For example , most v8 engine the cruising range is around 1600 to 2000 rpm , depending on the model . In that ranger the mileage will be best . At 2200 rpm the mileage starts to get noticeably lower . At 2400 rpm fuel mileage is even worse . At 2800 rpm the vehicle is very hard on fuel and at 3000 rpm it is guzzling fuel so fast you may see the gauge moving down .

The engines in stock car racing some times turn over 9,000 RPM . These cars get about 3 miles per US gallon . Your street vehicle engine will blow up before it would rev any where near that RPM , so don’t try it !

- Driving below the cruising range will also burn more fuel . At cruising speeds the engine turns very freely and easily which leads to optimum fuel mileage.

Below cruising speeds the engine requires more effort to turn , resulting in higher fuel consumption . This combined with stopping and starting is why the fuel mileage is lower in city driving .

- Driving at uneven speeds will consume more fuel . If you are moving the accelerator up and down a lot when driving the engine will keep changing its adjustments and will consume more fuel . If you keep your foot steady on the accelerator and keep your speed steady the engine can hold fuel feed steady and your mileage will be much better.

- Tailgating . Following the vehicle ahead of you to closely can lower your vehicles fuel mileage as it is taking in (breathing) some of the exhaust from the car ahead in stead of clean air with the oxygen the engine needs for proper combustion of the fuel. Following too close is a deadly and dangerous practice and as you see it can also cost you money and fuel mileage . Being followed too close at high speed , by another vehicle can also cause a wind drag on your vehicle , which can cause your vehicle to consume more fuel .

- Body damage . Can affect the aerodynamics or the vehicle which can lower the fuel mileage . Damage to the front of the vehicle , if it increases the wind resistance would be the worst to increase fuel consumption .

- Add on s . Such as external windshield visors , roof racks , running boards and mud flaps , if they increase the wind resistance of your vehicle can lower the fuel mileage .

- Junk in the trunk . Carrying unnecessary weight in the vehicle or in the trunk will lower the fuel mileage . Don’t use you trunk as a storage space . Carry only what you need . Don’t get in the habit of leaving unnecessary items in the trunk of your car , or in the box of your pick-up . As it accumulates you will be paying to haul that weight around , in lost fuel mileage .

- Though it is most common that smaller cars with smaller engines get better fuel mileage it is not always the case .

I have owned a small (older) 4 cylinder , car that run properly but did well to get 28 miles per gallon (imperial gallons) or about 21.5 mpg (us gallons)

I also owned a 4000 pound car with a 5 liter v8 engine that could get 35 mpg (imperial gallons) or 28 mpg (us gallons) if I drove it at 50 miles per hour (80 k m h).

The tail gate on Pick-up trucks causes wind resistance at highway speeds

which can lower fuel mileage . If you lower the gate for highway trips , this will remove that resistance and the fuel mileage will be better . You must secure any thing in the box if you drive with the tail gate down or removed .In some areas it may not be legal to drive with the tail gate down ?

The tail gate on most pick-up trucks , can be removed very easily . If you don’t need it , the tail gate could be removed for highway trips . There are also tail gate substitutes you can buy to replace the tail gate .Some are made of cloth belting and others are metal or mesh . When these are used in place of the tail gate , the air can pass through them , which lowers the wind resistance and improves fuel mileage . Hard shell box covers eliminate wind resistance completely , and mileage is better. Soft box covers of good quality and that are fit properly (tight) can lower wind resistance and help to improve fuel mileage . Poor quality or poorly fit soft covers (if they move up and down in the wind) will increase wind resistance and the fuel mileage will be worse .

The above information is meant to help you to get the best fuel mileage out of the vehicle you drive.