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Two Oldsmobiles with 5.7 L diesel engines and one with a 4.3 L diesel engine were tested to determine the effect of the low temperature properties of diesel fuel on operability (cold-start and warm-up driveability). Startability limits ranged from −18°C to −24°C and were unaffected by cetane quality of the fuel within the range of 39 to 50 cetane numbers. With untreated fuels, the cars would not operate when the fuel temperature fell below the cloud point of the fuel because wax crystals precipitated from the fuel and plugged the fuel tank filter. Low temperature operability was extended as much as 10°C by the use of fuel flow improver additives and a modified vehicle fuel system.

Although the control of nitrogen oxides from automobile exhaust is not yet required by law, several methods have been investigated to determine how much control is possible and what penalties result. These methods involved spark timing, carburetion, and exhaust recirculation. On one test car, a control system was developed which reduced nitrogen oxides 74% while maintaining hydrocarbon and carbon monoxide control at current (1968) federal levels. However, a 13% loss in fuel economy was incurred, and driveability problems were observed. Application to other car models, deposit accumulation, durability, and performance under extreme weather conditions are all open questions at this time.