sorry synthetic oil doesnt leak more or create leaks this is missinformation.i hjave used syn on and off for 30+ years and the oil real difference to the average driver is cost.i have used it in my harleys and 4x4's hotrods and muscle cars.synthetic oil producers say you can get more miles between changes because of its supperior quality..hmmm oil gets dirty from carbon deposits from combustion thats what kills bearings so who cares how long oil will last when they all get dirty at the same speed.do oil changes often and your engine will love you..mazda calls for 0/w20 its only available in synthetic so use it but change often thats the key to a long engine life..
FROM EXPERIENCE: Synthetic does not CAUSE leaks, but it will find leaks. Here's what I mean. I was using dyno oil in my old 2000 CR-V but finally the stuff got so close to Synthetic in price (when on sale) that I said screw it and started running synthetic. Within weeks after the change I started having an oil leak. It was the oil pan gasket which, due to age, had failed. Due to sludge and the conventional oil not flowing as well, the failure wasn't as noticeable. I am sure it was seeping a bit with the conventional oil but the synthetic leaked.
So what to do? Well, I did what any anal car owner would do; I paid the freight and replaced the oil pan gasket.
As far as this discussion, if you go to the parts houses, they run a special of 5 quarts of the "synthetic of the month" and a filter for around $30 bucks. At that price, I have absolutely no idea why anyone would run anything else. Now you can go to bobistheoilguy.com and get into the pissing contest of which synthetic is better, but really, even the most generic of synthetic is better than conventional. The motor oil doesn't just lubricate on a modern engine, but rather it acts as the hydraulic oil for all of the variable valve timing stuff as well as, to an extent, it's being used as coolant. SO you know, it's cheap insurance, every 5000 miles I do an oil change and I use synthetic.