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A study of one of the first batches of local low sulphur diesel fuels was conducted in order to determine the fuel's lubricity effects on VE rotary pump performance. This study involved a 30,000 km accumulation field test. Two types of fuels were used. Both were not additised with lubricity improvers. The first fuel, with HFRR WSD value of 358 μm, was used on three test vehicles, each fitted with new VE rotary pumps. The other fuel (HFRR value of 467 μm) was used with the other three test vehicles, each fitted with new pumps that were evaluated prior to field use. Camplate, cam-roller, pins and flyweight were evaluated after completing 30,000 km. No evidence of abnormal wear was found for all six pumps. However, slight but noticeable differences were found between pumps running on Test Fuels 1 and 2. These differences were found in flyweight stroke and axial wears. Despite these differences, the pumps were considered to be capable of further use.

Technical feasibility study of the use of two-way catalytic converters in two-stroke motorcycles was conducted by means of a 20,000 km field-test. Three 150cc two-stroke motorcycles were retrofitted with metallic monolith catalyst. After the field test, the catalytic converters were inspected and found to be structurally intact and devoid of oil. The catalysts were not chemically poisoned. At the end of 20,000 km accumulation, the catalysts were still effective towards HC reduction. However, their light-off temperatures were shifted. White smoke was significantly reduced. However, a CO rise was observed throughout - indicating partial oxidation of HC due to insufficient availability of oxygen.

As the consequence of air quality detenoration and the car overpopulation in Bangkok Metropolitan Area, unleaded gasoline was introduced in 1991 In using unleaded gasoline for cars with soft exhaust valve seats, their recession was found to be excessive after only 3000 - 12 000 km of usage on the highway at 120 km/h Such cars represented about 15 percent of the national car population in 1993 Using an anti-valve seat recession additive is one solution used to prevent valve seat recession An engine test simulating field conditions to evaluate additive effectiveness was implemented Potassium-based and sodium-based additives were tested and the test results led to the conclusion that the effective anti-valve seat recession additive treat rate suitable for car population and driving condition in Thailand was 10 mg of potassium or sodium per kg of fuel Unleaded gasoline with anti-valve seat recession additive has replaced leaded gasoline in Thai market as of 1995 Finally, leaded gasoline was completely phased out as of January 1, 1996 by Government regulation