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Diesel cars are sometimes refueled with gasoline by mistake. Already small amounts of gasoline are harmful for diesel fuel's lubricity, cetane number, viscosity and flash point, and may cause vapor bubbles. Cases are laborious to fix. Repair costs may be thousands of euros if fuel injection system break down has taken place. Misfueling of diesel fuel into gasoline is not common in cars but may take place in non-road engines refueled from canisters. This will cause engine oil dilution, reduced octane number and running problems. Adding of SCR-urea into fuels causes serious problems. Coolant and windshield washing concentrate may be added thinking that they help to dissolve water into fuel; only additives indented for fuels shall be used. Practice has shown that even automotive professionals may not know which misfuelings are serious and which are harmless. Some misleading advice has also been distributed by the media.

Hydrotreated vegetable oil (HVO) named NExBTL is a 2nd generation renewable diesel fuel made by a refinery-based process converting vegetable oils to paraffins. Also animal fats are suitable for feedstocks. Properties of this non-ester type biobased fuel are very similar to GTL. It contains no sulfur, oxygen, nitrogen or aromatics. Cetane number is very high (∼90). Cloud point can be adjusted by severity of the process from -5 to -30°C, heating value is similar to diesel fuel, storage stability is good, and water solubility is low. Emissions of two heavy duty engines and two city buses are presented with HVO and sulfur free EN 590 diesel fuel. The effect of HVO on regulated emissions compared to EN 590 fuel was: NOx -7 % … -14 % PM -28 % … -46 % CO -5 % … -78 % HC 0 % … -48 % Aldehydes, PAHs, mutagenicity and particulate size were also measured.

Hydrotreating of vegetable oils or animal fats is an alternative process to esterification for producing biobased diesel fuels. Hydrotreated products are also called renewable diesel fuels. Hydrotreated vegetable oils (HVO) do not have the detrimental effects of ester-type biodiesel fuels, like increased NOx emission, deposit formation, storage stability problems, more rapid aging of engine oil or poor cold properties. HVOs are straight chain paraffinic hydrocarbons that are free of aromatics, oxygen and sulfur and have high cetane numbers. In this paper, NOx - particulate emission trade-off and NOx - fuel consumption trade-off are studied using different fuel injection timings in a turbocharged charge air cooled common rail heavy duty diesel engine. Tested fuels were sulfur free diesel fuel, neat HVO, and a 30% HVO + 70% diesel fuel blend. The study shows that there is potential for optimizing engine settings together with enhanced fuel composition.

In a diesel engine, both physical and chemical properties of the fuel affect exhaust emissions. This study focused on the separation of some physical and chemical effects of the fuel on the NOx emission. The tests were conducted with a bus engine using four diesel fuels with different density and aromatics levels. The measurements were performed using five injection timing settings to screen the effects of changes in actual injection timing. When conventional diesel fuel was replaced by reformulated diesel, NOx was reduced 7-13 %. Changes in the injection timing due to differences in the physical properties accounted only for a minor part (10-25 % relative) of the total reduction of NOx, whereas the greater part of the reduction (75-90 % relative) was due to other reasons, mainly fuel chemical properties.

When a new type of fuel is introduced, it is necessary to ensure that exhaust gas aftertreatment systems work properly with these fuels. Today diesel particulate filter (DPF) is an inherent part of current diesel engine's exhaust gas aftertreatment system due to stringent exhaust emission limits. The functioning of DPF depends on the composition of soot particulates of exhaust gas, whereas the type of soot depends on the fuel used. To avoid clogging, DPF has to be regenerated regularly. This regeneration is usually increasing fuel consumption, so the longer the regeneration interval is, the better is fuel economy. Fuel quality and engine-out particulate emissions are important factors affecting to the need of regeneration. Renewable fuels burn cleanly and produce less particulate emissions than ordinary diesel fuel. Therefore, the increase of exhaust backpressure is slower enabling longer regeneration frequency.

Emissions of heavy duty engines using hydrocarbon fuels and rape seed methyl ester (RME) were measured according to the ECE R49 test procedure. The effect of fuel density on engine power was taken into account in the ECE R49 tests. The two reformulated fuels tested had sulphur below 50 ppm, aromatics below 20 vol-%, cetane number over 49 and reduced triaromatic content. Particulates were measured in a AVL Mini Dilution Tunnel 474 and gaseous unregulated hydrocarbons by Siemens FTIR. Reformulation reduced NOx by 5 to 12 %, particulates by 10 to 25 % and Ames mutagenicity by 56 to 74 %. RME increased NOx by 4 to 9 %, reduced particulates by 0 to 33 % and the mutagenicity by 17 %. Cetane number was found to be not important in reducing emissions. Low fuel triaromatic and low particulate PAH content reduced the mutagenicity of particulates.

Oxidation stability tests have been developed for estimation of the long term storage stability of diesel fuels. Currently, several oxidation stability test methods (eg. ENISO12205, Rancimat (EN15751), PetroOXY (EN16091)) are used for this purpose. It is common for these tests to have an elevated temperature and to add oxygen or air to accelerate the oxidation of the test fuel, and hence accelerate conduction of the test. It has been under discussion whether these tests actually represent real-life conditions. Also, it has been proposed that these oxidation stability tests could be used to estimate the thermal stability of the diesel fuels. In many cases the correlation to real-life is unclear. Stability of EN590 B0 (winter and summer grade) and B7, B30, EN590 with 30% HVO, 100% HVO, WWFC category 4 diesel, Swedish class 1 as well as the effect of cetane improver was evaluated with different oxidation stability methods.

Deposits formed on the plungers, barrels and delivery valves of some in-line injection pumps in diesel engines. The deposits formed during 5,000 - 20,000 km of driving and caused sticking of plungers. Normally the plungers, barrels and delivery valves keep clean. Deposits formed if kerosene based arctic diesel fuel containing lubricity additive was used. Small amounts of engine oil mix with diesel fuel in the pump. A chemical reaction between the fuel lubricity additive and the engine oil, which lubricates the camshaft of the pump, caused the deposits. The problem was avoided by changing the type and dosage of the fuel lubricity additive.