Gasoline Testing Program

A routine gasoline sample will be analyzed for most or all of the following parameters to meet specifications established in ASTM D4814. ASTM methods may be obtained by phone, fax or email from either the Reno or Las Vegas laboratories or by directly contacting ASTM International, or the volume may be purchased from:

ASTM International
100 Barr Harbor Drive
West Conshohocken, Pennsylvania 19428

Vapor Pressure by ASTM D5191

Vapor Pressure is a physical measure of gasoline volatility. High vapor pressures and a low distillation temperature for 10% evaporated both help cold starting.

In order to reduce overloading the vehicle's control systems, the Environmental Protection Agency (EPA) has placed maximum limits on gasoline's vapor pressure during the ozone season (May 1 - September 15). Also, the Washoe County Health Department has placed even lower vapor pressure requirements for ozone non-attainment areas of Washoe County during the period of June 1 - September 15. Hydrocarbon emissions are precursors to the formation of ozone (smog).

To assure that fuels have the proper volatility characteristics, refineries adjust gasoline seasonally. During the cold winter months, gasoline will be more volatile. This helps good "cold" start and warm-up performance. During the hot summer months, the gasoline is less volatile. This will help to minimize hot driveability problems.

Octane screen by Near Infrared Spectroscopy

Gasolines are most commonly rated based on their Antiknock Index (AKI), a measure of octane quality. The octane is a measure of gasoline's ability to resist knock or auto-ignition. The fuel-air mixture in the cylinder of a spark ignition engine will, under certain conditions, auto-ignite. This pre-firing may cause an audible "ping" or knock and may also cause an engine to continue running when turned off. Loss of power and damage to an engine can occur when knocking is severe and prolonged.

The AKI of a motor fuel is the average of the Research Octane Number (RON) and Motor Octane Number (MON) or (R+M)/2. This is also the number displayed on the black and yellow octane decal posted on the gasoline pump. Optimum performance and fuel economy is achieved when the AKI is adequate for the engine in which it is combusted. There is no advantage in using gasoline with a higher AKI than the engine requires to operate knock-free.

Improper octane fuel can lead to an increase in emissions of pollutants. Any fuels found in non-compliance have confirmatory analysis performed by an outside laboratory per ASTM D2699 and D2700.

Distillation by ASTM D3710

The "distillation" standard is one of several tests used to address gasoline's vaporization characteristics. Gasoline is metered in liquid form, through the fuel injectors (or carburetor), and mixed with air and atomized before entering the cylinders. Therefore, it is very important that a fuel's tendency to evaporate is controlled to certain standards. A fuel's ability to vaporize or change from liquid to vapor is referred to as its volatility. In gasoline, the distillation characteristics, along with vapor pressure, define and control starting, warm-up, acceleration, vapor lock, crankcase oil dilution, and, in part, fuel economy and carburetion icing.

The tendency of a fuel to vaporize is also characterized by determining a series of temperatures at which various percentages of the fuel have evaporated (boiling temperatures). The temperatures at which 10%, 50%, and 90% evaporation occurs are often used to characterize the volatility of gasoline.

The 10% evaporated temperature is directly affected by the seasonal blending of the gasoline. This temperature must be low enough to provide easy cold starting, but high enough to minimize the vapor lock and hot weather driveability problems. Most cool weather driveability problems occur from the use of summer season gasoline in the winter months. This is especially true in premium grades, which normally have a high 10% evaporated temperature.

The 50% evaporated temperature must be low enough to provide good warm-up and cool weather driveability without being so low as to contribute to hot driveability and vapor locking problems. This portion of the gasoline greatly affects fuel economy on short trips.

The 90% and end-point evaporation temperatures must be low enough to minimize crankcase and combustion chamber deposits, as well as spark plug fouling and the dilution of engine oil.

If the end-point temperature exceeds the ASTM maximum requirement, it is usually because of the presence of a distillate fuel such as No. 2 diesel. This contamination can be directly attributable to the delivery of diesel prior to the delivery of the gasoline. This problem is avoided if care is taken in handling the product.

Sulfur by ASTM D5453

Sulfur is an element that is normally found in varying amounts in all petroleum products. As a result of combustion, sulfur compounds of an acidic or corrosive nature are produced and contribute to combustion chamber and valve deposits, exceptional wear on the engine, and increased atmosphere pollution.

Oxygenates by ASTM D5599 and by IR Screening

An oxygenate, specifically ethanol, is a compound added to gasoline to provide more oxygen in the combustion process, thus decreasing the amount of carbon monoxide emitted from the vehicle.  Ethanol is used to meet wintertime oxygenate requirements in Washoe and Clark Counties. 

In addition, due to the Renewable Fuel Standard, most of the gasoline available in Nevada throughout the year will contain some amount (up to 10%) of ethanol.

As a result, samples from Clark and Washoe Counties are tested during the wintertime to ensure that a proper amount of ethanol has been added. Throughout the rest of the year, samples from all over the state are analyzed to ensure that no more than 10% ethanol has been added.

Water/sediment by Visual Inspection

Water and sediment in fuel is one of our program's most frequent consumer complaint. As most are aware, water makes a very undesirable fuel and sediment has a tendency to clog filters, carburetors and injectors. ASTM requires gasoline to be visually free of undissolved water, sediment, and suspended matter: it shall be clear and bright at ambient temperatures or 70° F, whichever is higher. The presence of water and/or sediment can lead to improper motor operation and thus excess emissions of pollutants.