In the additives section, Frank has asserted that synthetics degrade seals and contribute to or casuse seal leaks while dino chemistry does not. JB also has a post there asking about this in more technical terms but no one has replied. I thought I'd raise the issue in the main forum. Do today's synthetics, synthetic blends and high milege dino oils containing esters promote seal degradation and oil leaks. I'd be interested in knowing what the experts have to say on this.