Car Maintenance to Improve Gas Mileage

How Regular Maintenance Can Lead to Significant Fuel Savings

Car maintenance isn’t glamorous.  It’s one of those things we all know we have to do, but often put off or take short cuts around.  Keeping up your regular maintenance, however can give you a big payoff in the end.  Regularly changing your oil, maintaining your tires, and keeping your car’s mechanical system in good condition can improve your car’s gas consumption and extend the life of your vehicle. Let’s take a closer look at the different aspects of automobile maintenance and fuel conservation.


Motor Oil

All car owners know they have to change their motor oil periodically to keep your car under warranty and to maintain the internal parts of the engine. If you’re like me, you probably don’t think much about your oil beyond getting it changed every 3 months or 3,000 miles.  There are lots of brands and varieties, and your choice can make a difference in fuel efficiency as well as extending the life of your engine.

Motor oil does more then just lubricate the engine: it has four major functions:

  1. It reduces friction by lubricating all the engines moving internal parts.
  2. Cools the engine
  3. Control and reduces the contamination and corrosion of engine parts.
  4. Seals piston rings.

Different motor oils will affect your engine’s performance and therefore your fuel efficiency. Your owner’s manual will specify you what type of motor oil works in your vehicle, but that still leaves a wide range of choices. 


Understanding Oil Weights

Motor oil is labeled by its weight.  Although there are both single and multi grade oils, most cars and trucks use multi-grade oils. The Society of Automotive Engineers (SAE) set the viscosity grading system.  The two most common grades are SAE 10W-30 or SAE 10W-40.  The two numbers indicate the nominal viscosity of the oil during high and low temperatures.  The viscosity describes the amount of resistance a fluid has when it flows on its own.  If viscosity is high, the fluid does not flow easily, if it is low it does.  The first number of the motor oil grade indicates the winter weight, or how the oil will behave in the cold and the second number shows how the normal viscosity at 100 degrees C. Oil must be thin enough to flow in cold temperatures and stay thick enough to protect engine parts in hot temperatures.  Ultimately you want the oil to flow as easily as possible through the engine, that’s why many drivers switch to the lighter grade, 10W-30, during colder weather and 10W-40 when it is hot.  Many of the newer engines now use lighter oils with numbers like 5W-20 for higher fuel efficiency.


When purchasing motor oil, drivers can choose synthetic or non-synthetic oils.  Synthetic motor oils tend to last longer because they don’t chemically break down as quickly as conventional oils.[1] When oil breaks down it leaves sludge and deposits which can affect the efficiency and longevity of your engine. Synthetic oils are usually more expensive so you need to balance the cost of the oil with its benefits.  I’m choosing to pay a little more for the extra protection.


One last thought on choosing oil.  Look for the API energy conserving symbol on the label.  This indicates that it contains friction-reducing additives.


Air Filters

The air filter is part of your vehicle’s intake system.  Your engine needs both air and fuel to make it run.  The air filter keeps out dirt and other junk that would otherwise enter and possibly damage the engine. According to a 2009 study examining the effects of changing the disposable air filter on vehicle fuel economy, changing filters on fuel injected, computer controlled engines does not improve fuel economy.[2]  Most cars made since the early 1980s have fuel injected engines. If you have an older car with a carbureted engine, frequently changing your filter can improve fuel economy 2 to 6 percent and up to 14 percent if your filter is really clogged up. 

Although changing your air filter may not improve your vehicles fuel economy, it will improve your engines longevity.  The air filter should be changed every 30,000 miles or more frequently depending on atmospheric and driving conditions. Some air filters are easy to change, but others, especially in vans, are difficult and you probably want your mechanic to do it for you. 

You also have the option of buying disposable or reusable air filters.  Disposable filters are made of paper and or cotton on a plastic and or metal frame.  Reusable or Performance air filters are made with cloth or foam filtration air system which can improve the air flow to the engine.  The reusable air filters need to be cleaned less frequently then disposable filters. Check with the manufacturer for recommended cleaning schedules for individual cars and filters.


Fuel Injection System

As I mentioned above, most cars made since the early 1980s have a fuel injection system, which replaced the carburetor.  Over the decades the fuel injection system has evolved from a single point fuel injection system to a multi-port or sequential fuel injection system.  These systems have a fuel injector for each cylinder providing more accurate fuel metering and quicker response. 

In layman’s terms the fuel injector is just an electronically controlled valve that opens and closes many times per second. The amount of fuel that goes into the engine is determined by the length of time the fuel injector stays open.  The more efficiently your fuel injection system works, the better your fuel economy.[3]

There are fuel injection cleaners that cost a few dollars.  The cleaner is added to the gas tank when you have a full tank of gas.  The cleaner moves through the system and cleans the valves. You can also have your system cleaned by a technician with a fuel injection service.  This service often costs between $100 to $150.00.  Auto manufacturers do not recommend this service as regular maintenance, but sometimes suggest it as a fix for carbon knock.  You will get the best results from fuel injection cleaning if you regularly maintain your vehicle.  Cars that are in bad condition often show little improvement from either the cleaner or the service.



Choosing the right tires, keeping them properly inflated and properly aligned can have a major impact of fuel economy.  Many experts say the choice of tire can affect your gas mileage by as much as 10%.  The cost of the tire does not always translate to better gas mileage.  Read the label and ask the sales person about tires with the lowest rolling resistance.  Poorly inflated tires can hurt fuel efficiency an estimated 2.8% and reduces the life of the tire by as much as 10%.[4]

Proper alignment of your tires can save gas energy and human energy.  When your car is improperly aligned, your car you will burn extra gas when you redirect a car that natural wants to drift.  You may not realize it, but driving when your wheels are out of alignment, also makes your driving harder. 


Tune Ups

Bringing your car in for tune ups can improve your gas mileage by an average of 4% according to the U.S. Department of Energy.[5] Along with fuel savings, remember tune ups also help the longevity of your vehicle and certainly has a significant environmental impact. Even though newer cars need fewer tune ups, don’t ignore that “check engine light”.  The light can indicate dozens of problems, both large and small.  My light recently went off because of a leak in a hose that caused an increase in my fuels emissions.  By repairing that small problem, I reduced my car’s daily pollution.


Your Car’s Interior

When you think of car maintenance you may not think about your car’s interior, but when it comes to fuel efficiency cleaning out your car can make a difference.  If you tend to collect stuff in your trunk or back seat, you may end up hauling 50 pounds or more of unnecessary weight. That extra weight burns extra gas.  Don’t use your car as an extra storage space, keep it clean and save gas.



References  Effect of Intake Air filter Condition on Vehicle Fuel Economy   Feb 2009   prepared by Kevin Norman, Shean Huff, and Brian West.  Tires and Passenger Vehicle Fuel Economy, National Research Council of the National Academies, 2006

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