The design, assembly and operation of a vehicle-based, real-time data acquisition system for the engine and cooling system are discussed.Evaluations of 50% antifreeze in water were performed on level road and 5% grade courses at speeds ranging from 30 mph to 60 mph. These runs were repeated in a chassis dynamometer cell and were followed by similar tests employing 60 and 70% antifreeze in water under 90 F ambient air temperature conditions. More than 40 engine and cooling system parameters such as temperatures, pressures, flow rates, engine spark timing. etc. were recorded to assess the performance of the vehicle and cooling system at each concentration of antifreeze and water.Data are compared to those from laboratory tests of other modern day vehicles and with data from experiments performed in cars during the 1960's with various concentrations of antifreeze in water.TYPICAL LABORATORY TESTING OF AUTOMOTIVE ENGINE COOLANTS involves a combination of bench tests, engine test stands and fleet tests. The latter usually means sampling of the coolant and metal specimens at certain intervals with little attention paid to the operating conditions in the cooling system. Until recent years the equipment required for on-the-road, high speed data acquisition has been either prohibitively expensive or too large to be conveniently transported and operated. However, advancing technology has resulted in “portable”, high speed computers capable of communicating with data acquisition devices and capturing a large number of parameters in real time. On-screen graphics allow for display of obtained data in tabular or graphical form while it is being acquired. Thus, it is possible to profile temperatures, pressures, heat flux, and flow rates throughout the system as well as engine parameters such as ignition timing.This paper discusses the development of such a data acquisition system, the installation of the necessary sensors in a late model car and the problems encountered. The system has been used to fully characterize 50%-70% ethylene glycol in water to determine the effect on engine and cooling system performance. Data are compared to similar work performed in a chassis dynamometer cell with vehicles from the 1960's and other modern day vehicles. Throughout this paper, the term “coolant” will refer to mixtures of ethylene glycolRbased antifreeze and water.