A diluter apparatus and a method for sampling of exhaust gas of engines, wherein the diluter has a primary capillary connected to a primary stabilizing chamber. The primary stabilization chamber is kept at a pressure below ambient by means of a vacuum pump connected to the primary stabilization chamber by means of a primary outlet duct and where dilution air in the primary stabilization chamber is introduced by means of a primary dilution air duct through a primary mixing tip, wherein there is provided an excess flowrate arrangement for providing an exhaust gas flowrate in excess of the sample flowrate in the capillary. Exhaust gas flowrate totally surrounds the capillary inlet tip, wherein the primary capillary is immersed in the exhaust gas flowrate with flowrate arrangement, and wherein the diluter receives the exhaust gas via said primary capillary.