The Claim:

“There are things that you can do individually, though, to save energy, making sure your tires are properly inflated — simple thing — but we could save all the oil that they’re talking about getting off drilling, if everybody was just inflating their tires.  And getting regular tune-ups, you could actually save just as much.”

-- Barack Obama 7/30/08 Springfield, MO (YouTube video)

This claim has been evaluated by PolitiFact.com and they found it to be true.  Numerous other media organizations have also looked into the potential savings and have come to the same conclusion.  We disagree and we believe that previous media analyses have been faulty for a number of reasons.

As will be shown in the following paragraphs, the actual savings is far less than what just a few oil wells in the Gulf currently produce, and is not even remotely close to saving "all the oil that they’re talking about getting off drilling."

Three questions must be answered to evaluate this claim:

1. How much can we actually save if everyone had properly inflated tires?
2. How much can we actually save if everyone had properly tuned vehicles?
3. How much oil are they talking about drilling?

Tire Inflation Savings Potential
In order to determine how much gasoline could be saved by properly inflated tires, we need to know how much under inflated tires impact fuel economy and how many vehicles have under inflated tires.

Fuel Economy Impact
The Department of Energy says that having four poorly inflated tires will cause the average mid-size sedan to use an additional 0.5 - 0.6 gallons of gasoline per 1000 miles, or stated another way; reduce fuel economy by about 1 - 2%.

The Transportation Research Board, in a 2006 report on Tires and Passenger Vehicle Fuel Economy (page 126), found that having four under inflated tires will increase rolling resistance by about 1.4% for every pound per square inch (psi) below the recommended pressure and that a 10% increase in rolling resistance corresponds to a 1 - 2% decrease in fuel economy.

The highest estimate comes from a Department of Energy fuel economy and car maintenance tip sheet.  The tip sheet states that "you can improve your gas mileage by around 3.3 percent by keeping your tires inflated to the proper pressure" and that "under inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires."  The same sheet also identifies the fuel economy benefit as "up to 3%."

These three sources indicate a total potential of somewhere between a 1% and 3% decrease in fuel economy for vehicles with four significantly under inflated tires.  The two lower estimates are based on detailed scientific studies and should carry more weight than the high estimate, which is stated as being based on literature reviews.

Number of Vehicles/Tires
The Department of transportation conducted field research in February of 2001 and examined over 11,500 vehicles randomly at gas stations to determine the number that had under inflated tires.  As is widely quoted in the media, the study found that 27% of passenger cars and 32% of light trucks had one or more under inflated tires.  Those media reports either fail to mention or do not understand the significance of the "one or more" in that summary of the findings.

The data from Table 7 on page 9 in the Tire Pressure Special Study - Vehicle Observation Data indicates that 14% of cars and 13% of light trucks had one under inflated tire, 7% of cars and 10% of trucks had two, 3% of cars and 4% of trucks had three, and 3% of cars and 6% of trucks had all four tires under inflated.  From this information, it can be calculated that 12.25% of all car tires and 17.25% of all light truck tires are under inflated.

There are about 135 million cars and 105 million light trucks registered in the U.S.,  which indicates there are 540 million tires on cars and 420 million tires on light trucks.  Based on the previous calculation of 12.25% under inflated car tires and 17.25% under inflated light truck tires, it can be determined that approximately 66.15 million car tires and 72.45 million light truck tires are under inflated.  Adding those two numbers yields 138.6 million under inflated tires or about 14.44% of all tires on light vehicles.  Dividing 138.6 million tires by 4 indicates that the equivalent of 34.65 million light vehicles have four under inflated tires.

Fuel Savings
Approximately 390 million gallons of gasoline are produced and consumed daily, which works out to about 142 billion gallons per year.  Using the 14.44% figure derived above, it can be determined that about 56.3 million gallons a day, or 20.5 billion gallons a year, are consumed by vehicles with four under inflated tires.

Using the Fuel Economy Impact information previously presented, between 1% and 3% of those 56.3 million gallons per day are wasted by vehicles with four under inflated tires.  This indicates a range of between 563,000 and 1.69 million gallons per day impact, which equates to between 205.5 million and 616.5 million gallons per year. 

Dividing the total impact (205.5 to 616.5 million gallons per year) by the total number of vehicles affected (34.65 million) yields a potential savings of between about 6 and 18 gallons per year per vehicle with four under inflated tires.

All of these numbers are far lower than the 2.8 billion gallons a year total impact and 44 extra gallons per vehicle per year that was computed by AAA and widely reported in the media.  The reason for this is that they used the 27% and 32% number of vehicles with under inflated tires directly instead of properly computing the actual percentages that had four under inflated tires.  They also used 10% instead of 1% - 3% for the fuel economy impact.

Another widely reported number is 1.2 billion gallons per year of gasoline wasted by under inflated tires.  This comes from a Government Accountability Office (GAO) letter dated February, 9, 2007.  It states that cars and light trucks used an estimated 130 billion gallons of gasoline in 2006 and that "DOE’s designated economist on this issue estimates that vehicles with under inflated tires waste approximately 1.2 billion gallons of fuel per year due to the increased resistance of the tires."  This estimate is not found in a search of published studies or other documents by DOE or DOT and may be a "back of the envelope" calculation.  We believe we have recreated the methodology used and will demonstrate that it is flawed in a manner similar to AAA estimates.

1. 135 million cars multiplied by 27% equals 36.45 million with under inflated tires.
2. 105 million light trucks multiplied by 32% equals 33.6 million with under inflated tires.
3. Total light vehicles with under inflated tires would be 36.45M + 33.6M or 70.05M.
4. 130 billion gallons of gasoline total used per year divided by 240 million light vehicles equals 541.67 gallons per vehicle per year.
5. Multiplying 541.67 gallons by 70.05 million vehicles equals about 37.944 billion gallons.
6. Multiplying 37.944 billion gallons by a 3.2% mileage impact equals 1.214 billion gallons per year wasted.

As indicated in the Number of Vehicles/Tires section, the actual percentages of vehicles to use are 12.25% of cars and 17.25% of light trucks, not 27% and 32%, which accounts for most of the discrepancy between the computations of gasoline wasted.  The remaining discrepancy reflects the use of a 3.2% loss versus a 1% - 3% loss as indicated the Fuel Economy Impact section.

The actual amount of gasoline wasted by light vehicles with under inflated tires is between 563,000 and 1.69 million gallons per day and between 205.5 million and 616.5 million gallons per year.

Tune-up Savings Potential
In order to determine how much gasoline could be saved if all cars were properly tuned, we need to know how many vehicles are improperly tuned and how much impact an improperly tuned vehicle has on fuel economy.  The required information is not readily available, but we can make a few assumptions to get a conservative ballpark estimate. 

Number of Vehicles
According to a 2005 report by R.L. Polk, 34.8% of the light vehicle population is 11 years of age or older.  This is important because in 1996 new regulations went into effect requiring automakers to install a sophisticated on-board diagnostic (OBD) system using computers and sensors that essentially act like a built-in state emissions testing station. The computer monitors and adjusts dozens of components and processes to maintain optimum performance.  Unless the check engine light is on, nothing really needs to be done as far as a tune-up.  Many cars manufactured before 1996, especially high-end models, also included similar monitoring capabilities.

While some newer vehicles are undoubtedly being driven with the check engine light on, the actual number of them is not available.  Also not available is the average length of time the light stayed on before service was performed, which would be required for any reasonably accurate estimate.  For our purposes, we will use an arbitrary yet conservative assumption that 10% of the light vehicles on the road at any given time are driving around with the check engine light on and thus in need of service.  Using 65.2% of the fleet as being equipped with the sophisticated computer systems and sensors (156.5 million vehicles) and the 10% assumption, there would be about 15.65 million newer vehicles requiring service.

For older vehicles, we can deduce that something less than 34.8%, about 83.5 million, still need regular tune-ups and maintenance to detect and correct problems since they do not have OBD.  There is no data that identifies the actual number of these vehicles that may be out of tune so we will use an arbitrary yet conservative figure of 15%, which would be about 12.5 million vehicles.

Combining those estimates gives 28.15 million vehicles requiring service, which should be well above the actual number of such vehicles on the road.  The actual number is likely less than 10 million considering that 33 states and the District of Columbia have some form of emissions inspection, which a vehicle more than slightly out of tune would fail, and those states are home to almost 180 million of the 240 million total light vehicles.

Fuel Economy Impact
According to the fuel economy and car maintenance tip sheet referenced earlier, "Fixing a car that is noticeably out of tune or has failed an emissions test can improve its gas mileage by an average of 4 percent, though results vary based on the kind of repair and how well it is done."  No research uncovered any studies to dispute that claim, so an average of 4% savings will be used.

Fuel Savings
Approximately 390 million gallons of gasoline are produced and consumed daily, which works out to about 593 gallons per year per light vehicle.

The estimated 28.15 million light vehicles out of tune would therefore use about 16.7 billion gallons of gasoline per year.

An average fuel economy improvement of 4% after a tune-up multiplied by 16.7 billion gallons would indicate that a maximum of about 668 million gallons of gasoline are wasted each year by light vehicles that are out of tune, roughly 24 gallons per year per vehicle.

The actual amount of gasoline wasted by light vehicles that are improperly tuned is almost certainly significantly less than 1.83 million gallons per day and 668 million gallons per year.

Drilling and Potential Production
In order to determine how much additional oil could be obtained from drilling in areas currently under moratorium, we need to identify how much oil there is in each location and what reasonable production rates might be.  They are talking about drilling for oil off both coasts, in the eastern Gulf of Mexico, and in ANWR (not to mention oil shale, other Alaska, or natural gas). 

Outer Continental Shelf (OCS)
The OCS areas currently under moratorium encompass about 574 million acres and about 43 million acres other acres of the OCS are currently under lease.  Those acres under lease account for about 1.35 million barrels per day, which is about 27% of total domestic production.  This comes almost entirely from the western and central Gulf of Mexico.

The U.S. has nearly 21 billion barrels of proved crude oil reserves, with about 4 billion proved in the OCS areas.  There are an estimated 86 billion barrels of undiscovered crude oil and 420 trillion cubic feet of natural gas in the OCS area.  Exploration and drilling are required to convert any of those mean estimates into proved reserves.

The only estimate of production rates in the OCS was performed in early 2007 and quotes from it have been used extensively by politicians and the media.  The quotes always indicate that production would only increase by about 200,000 barrels per day in 2030 if access to the OCS areas under moratorium were allowed.  No projections are made beyond 2030 when, presumably, the bulk of production would be expected to come on-line.  The estimate has some assumptions that have since been overcome by events that would drastically change the results.

Foremost among these events is the price of crude oil.  The forecast assumed oil prices would range between about $40 and $60 throughout the projection period; that assumption also drives other assumptions in the forecast about the commercial viability of drilling in certain areas and just how quickly new production would be brought on-line.  The forecast also assumed that the OCS moratorium would remain in effect until 2012 and leasing could begin no earlier.  It further assumed that nothing beyond minimal exploratory drilling would begin before 2017 and that production would proceed at the pace of early western Gulf development after that.  These assumptions did not consider the experience gained from so much drilling in the Gulf and the effects the current high price of oil would have politically and economically on how soon to allow drilling to begin.  Some sources say a million barrels per day or more of production from the OCS in 2025 is more likely.

Arctic National Wildlife Refuge
The potential recoverable oil in ANWR is estimated at over 10 billion barrels and production levels are projected at from 650,000 to 1.9 million barrels per day.  The production of ANWR oil is estimated to cost $25 per barrel.  ANWR would begin at about 25,000 barrels a day in the first year of production and quickly grow to over a million barrels per day in 5 years.

Total Potential production
Based on extremely conservative government estimates, it can be concluded that a minimum of 200,000 barrels of oil per day would be produced in the OCS areas and a minimum of 650,000 barrels of oil per day would be produced in ANWR if the current moratoria on drilling in those areas were lifted.

The actual amount of oil that would be produced from opening the OCS and ANWR to exploration and drilling is an absolute minimum of 850,000 barrels per day in just 5 or 6 years after restrictions are lifted and more likely than not significantly higher.

Findings
We have determined that a maximum of 616.5 million gallons per year (1.69 million gallons per day) are wasted by under inflated tires on light vehicles and that a maximum of 668 million gallons per year (1.83 million gallons per day) are wasted by improperly tuned light vehicles.  We will need to convert the gasoline numbers into their equivalent barrels of oil per day in order to compare them with production requirements.

Based on refinery inputs and outputs, it can be determined that our refineries currently produce an average of a little over 23.4 gallons of gasoline from every barrel of oil (ignoring the diesel, jet fuel, and other finished products produced from that same barrel of oil).  This is determined by subtracting barrels of blending components (684M) from total finished gasoline (9,061M) for the week of 8/1/08.  The result, 8,377M gallons of actual gasoline produced, divided by total crude oil input for the same week (15,039M) will give us an oil to gas conversion ratio for that week (note that the ratio does vary slightly from week to week depending on the percentage of "sweet" crude versus "sour" crude).  The result is in an approximate conversion rate of 55.7% for oil into gasoline.  Since a barrel contains 42 gallons, multiplying 42 by 55.7% indicates that each barrel of oil produced about 23.4 gallons of gasoline.  Additionally, it also indicates that about 1.8 barrels (or gallons) of oil were required to produce 1 barrel (or gallon) of gasoline.

Multiplying 1.69 million gallons of gasoline per day by 1.8 indicates that just over 3 million gallons of oil per day are required to produce that amount of gasoline.  Dividing that by 42 yields an absolute maximum of 72,429 barrels of oil per day wasted by under inflated tires.  The actual number is somewhere between 21,142 and 72,429.

The same process indicates that nearly 3.3 million gallons of oil per day or an absolute maximum of 78,429 barrels of oil per day are wasted by poorly tuned vehicles.

Under inflated tires use a maximum of an additional 72,429 barrels of crude oil daily and poorly tuned vehicles use a maximum of an additional 78,429 barrels daily.

Conclusions
Senator Obama's claim that we could save all of the oil from drilling by inflating our tires is fiction.

Senator Obama's claim that we could save all of the oil from drilling by getting a tune-up is fiction.

Campaign staffers and others have interpreted his statements as meaning between both tires and tune-ups we could save more oil than drilling in the OCS areas would provide.  You can decide for yourself if Mr. Obama meant both inflating your tires and getting regular tune-ups as well as if he meant only drilling in OCS areas after listening to his statements.  Even assuming his tire and tune-up statements were linked and assuming they only applied to production in the OCS areas, since the savings would only represent an absolute maximum of about 3/4 of the highly conservative estimate of 200,000 barrels per day from OCS development that is so often quoted, they are still fiction.

That being said, using up to 151,000 less barrels of oil per day is not insignificant and all candidates should help to educate the public in order to achieve saving as much of whatever the amount of wasted oil actually is as possible.  Keeping your tires properly inflated and your car tuned is good practical advice.  Tires inflation is a safety issue in addition to an economic issue as under or over inflated tires adversely affect both the handling and braking abilities of a vehicle, especially on wet roads.  For additional car safety information and tips, visit safercar.gov.  Teachers and students may be interested in reviewing the Energy Action Challenge.