The authors of the paper present the methodology and results of experimental and theoretical studies of the effect of magnetic fields on the process of mixture formation and combustion of gasoline fuel in internal combustion engines to improve the environmental safety of cars. Experimental studies were carried out in a scientific laboratory engineering vehicles tests and in city traffic in compliance with national standards. Measuring instruments, by means of which studies have been conducted, are tested by the State metrological service in accordance with the laws of the Russian Federation. The proposed method consists of simultaneous action of constant magnetic flux of different polarity on the fuel and air which are the basic components fuel supply systems of vehicles equipped with petrol engines. During studies are used permanent magnets of two types: round (d = 41mm, height 10mm, the magnetic flux density (B) = 0.28T) and prisms (50 × 20 × 10, B =0.31T) in various combinations: 1 - one round magnet on the fuel pipe and one on the air inlet manifold; 2 - three round stacked magnet on the fuel pipe and three stacked on the inlet air manifold; 3 - three stacked magnets on air manifold, and three magnets along the fuel pipe with offset 120 degrees and staggered; 4 - two prismatic magnet on the fuel pipe and two on air intake manifold with an offset in 180 degrees in a staggered manner; 5 - two round magnets on the fuel pipe and two on air inlet manifold with 180 degrees offset and staggered. Laboratory tests were carried out on the vehicle class M1 with carbureted gasoline engine, which is not equipped with exhaust gas neutralization system. We investigated the most disadvantaged on toxicity of idling, minimum, and maximum engine speed. We studied the temperature and composition of the exhaust gases. As a result of experimental studies, in the exhaust gas obtained decrease toxic components such as carbon monoxide, from 16 to 40%, hydrocarbons from 2 to 20%, nitrogen oxides from 1.25 to 35% for the minimum engine speed, and the reduction of CO from 0.2 to 20%, CH 12 to 40%, NOx by 10 to 14.9% for higher engine speed. The proposed methodology, in comparison with the previously known, is the most simple and cheap way to improve the environmental safety of vehicles equipped with an internal combustion gasoline engines.