One thing to remember w the taxi cab test though is that they get 6K mi fairly quick, no time for oil to get 'old'....depending on driving habits change oil differently....town or freeway etc... I change ev. 6 mo. in my bird , never get more than 2K in 6 mo., in my old Volvo I changed ev. 5K, my Caddy goes about 5 - 6 K before change...the 88 Landcruiser we use we change ev 3K....
