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It is widely known that different factors, such as cold properties of a fuel as well as a vehicle design, affect the cold operability limit of vehicles. In this study, the aim was to get a better understanding of the properties of modern Light Duty Diesel (LDD) vehicles (2014-2020) that define their cold operability temperature limit. Moreover, the aim was to find out what a responsible fuel producer can do, in addition to providing a proper fuel that meets the specification, to ensure that a vehicle stays operable at cold temperatures. Similar study was done 10 years ago by Neste with the LDD vehicles of that time [1]. Therefore there was a need to update the info to concern the modern LDD vehicles. In this study the operability limit difference between the worst and the best operating LDD vehicle was >10°C (nbr of LDD vehicles = 5) with the same fuel. The limits were determined in a cold chamber using a chassis dynamometer.

For decades, ENISO12205 test has been used to evaluate the long term storage stability of diesel fuels. Nowadays, new biocomponents especially FAME has increased the need to create faster and more appropriate test method to measure the long term storage stability. Developments in engine technology have also raised the need to create a new method to evaluate the thermal stability of diesel fuels. These new methods should have correlation to field experience. As an example it has been shown that Rancimat (EN15751) and PetroOXY EN16091 have a correlation when fuel contains more than 2% FAME. Rancimat is not applicable for FAME free fuels, so correlation based PetroOXY limit should be limited to fuels containing more than 2 vol% FAME. Study on oxidation stability test methods and their correlation to real life were continued and deepened (part 1: SAE 2013-01-2678). ENISO12205 and PetroOXY EN16091 test methods did not have a correlation according to the earlier studies.

Cold operability is estimated by fuel's cold filter plugging point (CFPP). However, correlation of CFPP with diesel vehicle performance originates from a period when simple in-line or distributor fuel injection systems were applied and fuels did not contain biocomponents. Today, common rail fuel injection systems are used and there seem to be remarkable differences in their design between vehicle models. Seven cars were tested in a climate chamber. The best cars operated down to 8°C below fuel's CFPP but the worst get into problems 5°C above CFPP with the same fuel. It is challenging to define what CFPP is needed in order to guarantee trouble-free winter performance because there are big differences between car models. It is fundamental to get the fuel temperature of a vehicle's fuel filter above the fuel's cloud point during driving, and this depends on fuel system design factors, such as location and size of fuel filter and fuel heater if it is used.