Pleasant surprise

Sir,
With some trepidation I filled up my 1988 Volkswagen Golf GTi with lead-free fuel, fearing the sort of performance-loss that I experienced with detoxed American cars a decade ago. To my surprise, the engine seems to run more smoothly, and is less prone to stall. The exhaust seems richer, but there is no obvious temperature increase of oil or water, and performance seems unaffected. Is this just my imagination, or can your readers confirm this?

Dr Stefan Cembrowicz, Clifton, Bristol