A study conducted by Lancaster University Management School has revealed that levels of customer satisfaction were on average 20% higher in restaurants that employ staff aged 60 and over.
More than two-thirds of people surveyed said older workers connected well with customers, while 47% said they went the extra mile.
The study also revealed 44% believed workers aged over 60 brought mentoring skills to the workplace, helping younger colleagues develop and mature.
Professor Paul Sparrow, who undertook the study, said the results showed the value of employing older workers.
He said: "For McDonald's, we can show that the presence of older employees improves customer satisfaction and, in a service-led business, this drives the bottom line.
"Mature employees are a key part of the performance recipe.
"Employers must rise to the challenge of adapting to Britain's ageing workforce and this research shows that there can be a sizeable prize at stake for those which succeed."