A process for preparing a gas oil cut comprises the following steps in succession: 1) oligomerizing an olefinic C2-C12 hydrocarbon cut, preferably C3-C7 and more preferably C3-C5; 2) separating the mixture of products obtained in step 1) into three cuts: a light cut containing unreacted C4 and/or C5 olefinic hydrocarbons, an intermediate cut having a T95 in the range 200-220° C. and a heavy cut comprising the complement; T95 being the temperature at which 95% by weight of product has evaporated, as determined in accordance with standard method ASTM D2887; 3) oligomerizing the intermediate cut obtained in the separation step; characterized in that in step 3), oligomerization is carried out in the presence of an olefinic C4 and/or C5 hydrocarbon cut in a weight ratio of intermediate cut to olefinic C4 and/or C5 cut in the range of 60/40 to 80/20.