Samples of soybean oil which remained after laboratory samples had been taken from each of three batches, differentiated by type of initial preparation (frying potato chips, frying breadcrumbs coated fish fingers and heating without fried product), were separately subjected to esterification with methanol. Fatty acids methyl esters were obtained by method analogous to the one used in investigation of fatty acids composition by means of gas chromatography. Fuel obtained this way was used in engine tests including main engine work parameters. Four mixtures were prepared, each containing 90% diesel fuel and 10% addition of fatty acids methyl esters obtained in research and marked as:

a. M1 — esters obtained from purchased fresh soybean oil,

b. M2 — esters obtained from soybean oil subjected to five-time cyclic heating, without addition of fried product,

c. M3 — esters obtained from soybean oil, previously used for five-time cyclic frying of potato chips,

d. M4 — esters obtained from soybean oil, previously used for five-time cyclic frying of breadcrumbs coated fish fingers.

Results of internal combustion engine running on diesel fuel (DF) were used as reference for determination of work parameters of engine powered with fuel blends. Above mentioned fuel mixtures, were used for powering 2CA90 diesel engine installed on dynamometric stand for purpose of conducting measurements of its energetic work parameters. Test bed comprised of following devices:

— internal combustion diesel engine 2CA90;

— dynamometric stand composed of eddy-current brake AMX210 and control — measurement system AMX201, AMX 211;

— fuel consumption measuring system;

— system measuring engine parameters: exhaust gasses temperature — tsp, engine oil temperature — tol, oil pressure — pol;

— system measuring state of environment: temperature of environment — tot, atmospheric pressure — pa, and air humidity — ф.

Measurements for each of investigated fuels were conducted and obtained results of energetic parameters were elaborated. Data yielded by measurements was used to draw external characteristics of the engine for rotational speed ranging from minimal to nominal. Carried out research included kinematic and dynamic parameters of the engine: torque — Mo, rotational speed — n, time in which set amount of investigated fuel was used — t. Amount of fuel used for purpose of this characteristic was 50 g. Methodology of measurements and methods of measurements and results reduction of power and torque, were in conformity with norms: PN-88/S-02005, BN-79/1374-03.