Effect of Unleaded Fuel on Lubricant Performance 710584
The performance of motor oils in engines run on unleaded fuels was evaluated using several makes of United States cars. These oils, SAE 10W-40 grades, were run in high mileage or turnpike service, as well as surburban service. The performance with unleaded fuels was not significantly different from that for leaded fuels in the areas of wear, sludge, varnish, or rust.
Valve seat recession was detected in several of the cars, but had an effect on performance in only one case.
Further testing using laboratory engines and a patrol fleet in pursuit service demonstrated the effect of lubricant composition on valve seat recession. In addition, it was found that engines preconditioned on leaded fuels afforded better protection against valve seat recession than new engines.