Effects of UV Light

Importance of Protecting Samples and Reference Fuels for Octane Number Testing From Exposure to Sunlight 

After recent experiments at various Laboratories they have demonstrated that samples of Gasoline fuel collected in clear glass bottles may change dramatically when measured in the CFR Octane engine, if allowed relatively short periods of exposure to sunlight (any UV light). 

Impact on Fuel Suppliers and Regulators 

​There are two areas of concern. First, for fuels suppliers, there is a need for accuracy of internal measurements for process monitoring and certifying gasoline fuels for sale. Second, regulatory scrutiny is a constant and ever increasing process.

Fuel producers, regulators and end users may be compromised, if field samples yield results that do not truly represent the material sampled. Some regulatory agencies and segments of the industry (e.g. terminals, private inspection companies,) continue to permit clear glass bottles for field sampling. Although sampling instructions may suggest avoiding clear bottles in certain instances, ambiguity continues to exist in sample container selection.  


The results of these test showed that when gasoline fuels are exposed to sunlight (any UV light) over a short period of time it dramatically changed the octane number usually decreasing the number by as much one octane number.  

Therefore it is important that exposure to sunlight is avoided when the fuel is destined to be tested by the Octane engine. 


To exclude sunlight (any UV light) from samples destined for Octane Number determination. Clear glass is highly transparent and well into the UV range, while amber glass provides substantial protection. 

All reference fuels and standards relevant to Octane determination preclude the use of clear glass containers. 

To drain all reference fuel out of the burettes at the end of each day.