Thread: Adding 2 stoke oil to your diesel

Originally Posted by Bush65

I only read the beginning of the 1st post in that linked thread.

I'm surprised how many people think Sulphur was in diesel fuel for lubrication. It is an impurity, and unlike TE Lead was not for lubrication.

However, the cheapest way for refineries to reduce the Sulphur content in diesel, does have the side effect of reducing lubricity.

As John points out, organic sulphur (dibenzothiophene), found as an impurity in diesel and other fuels, has been found to have no effect or even a detrimental effect on lubricity. Below is the most comprehensive study I have to hand on lubricity additives (focussed on biodiesel).

Lubricity of components of biodiesel and petrodiesel. The origin of biodiesel lubricity

Author(s): Knothe G, Steidley KR
Source: ENERGY & FUELS Volume: 19 Issue: 3 Pages: 1192-1200 Published: MAY-JUN 2005
Times Cited: 37 References: 59 Citation MapCitation Map
Abstract: An alternative diesel fuel that is steadily gaining attention and significance is biodiesel, which is defined as the monoalkyl esters of vegetable oils and animal fats. Previous literature states that low blend levels of biodiesel can restore lubricity to (ultra-)low-sulfur petroleum-derived diesel (petrodiesel) fuels, which have poor lubricity. This feature has been discussed as a major technical advantage of biodiesel. In this work, the lubricity of numerous fatty compounds was studied and compared to that of hydrocarbon compounds found in petrodiesel. The effects of blending compounds found in biodiesel on petrodiesel lubricity were also studied. Lubricity was determined using the high-frequency reciprocating rig (HFRR) test. Dibenzothiophene, which is contained in nondesulfurized petrodiesel, does not enhance petrodiesel lubricity. Fatty compounds possess better lubricity than hydrocarbons, because of their polarity-imparting 0 atoms. Neat free fatty acids, monoacylglycerols, and glycerol possess better lubricity than neat esters, because of their free OH groups. Lubricity improves somewhat with the chain length and the presence of double bonds. An order of oxygenated moieties enhancing lubricity (COOH > CHO > OH > COOCH3 > C=O > C-O-C) was obtained from studying various oxygenated C-10 compounds. Results on neat C-3 compounds with OH, NH2, and SH groups show that oxygen enhances lubricity more than nitrogen and sulfur. Adding commercial biodiesel improves lubricity of low-sulfur petrodiesel more than neat fatty esters, indicating that other biodiesel components cause lubricity enhancement at low biodiesel blend levels. Adding glycerol to a neat ester and then adding this mixture at low blend levels to low-lubricity petrodiesel did not improve petrodiesel lubricity. However, adding polar compounds such as free fatty acids or monoacylglycerols improves the lubricity of low-level blends of esters in low-lubricity petrodiesel. Thus, some species (free fatty acids, monoacylglycerols) considered contaminants resulting from biodiesel production are responsible for the lubricity of low-level blends of biodiesel in (ultra-)low-sulfur petrodiesel. Commercial biodiesel is required at a level of 1%-2% in low-lubricity petrodiesel, which exceeds the typical additive level, to attain the lubricity-imparting additive level of biodiesel contaminants in petrodiesel.

Originally Posted by Panya

Wouldn't increasing the lubricity of the fuel simply help the fuel pump survive a bit longer? Surely not a huge amount of lubrication on engine moving parts from the fuel? I thought that's why we have engine oil!? I cannot get my head round the comment about the engine being in "extroardinary clean and top condition" from oil added to the fuel...

I think he's saying that the 2-stroke also improves combustion efficiency (in addition to lubricating the pump/injectors). This could result in a cleaner engine due to less soot production.