Re: Just went Synthetic
Sludge really isn't an issue with most of today's modern quality motor oils.<br /><br />The Toyota sludge problem is well known, and is the result of an engine design flaw.<br /><br />Sludge isn't necessarily related to thermal break-down of the oil. Plain and simple, sludge is caused by contaminates. Modern detergent oils (dino or synthetic) suspend the contaminates so they don't settle onto the engine, forming sludge. When the oil becomes saturated with contaminate particles, new particles settle out of the oil and on to the engine parts, and form the sludge. <br /><br />Synthetics don't prevent the contaminates from forming, however they my marginally suspend more contaminate particles, but not enough to prolong change intervals much. This is why it is important to follow the engine makers change interval, regardless of the oil used (or at least install a bypass filtrations system to help). IMO, any benefits of using a synthetic oil which may suspend more contaminates, is lost by extending the drain interval. Six of one, half a dozen of the other.<br /><br />IMO, the reason you see more sludge around the valve springs and valleys is because, as you say, the oil doesn't move much there. And these are prime spots for the contaminates, which can't remain suspended in the oil, to settle out. I don't believe it's a temperature issue, however I will acknowledge that excessive temperatures on oil can deplete the detergents and additives in any oil quicker. But engines, their specified change intervals, and modern oils have virtually eliminated sludge concerns.<br /><br />BTW, if you want to split sludge hairs, I would recommend staying away from naphthenic-based oils, which are more likely to form sludge due to their lower breakdown resistance. I can't remember the last time I saw one of those though.
Sludge really isn't an issue with most of today's modern quality motor oils.<br /><br />The Toyota sludge problem is well known, and is the result of an engine design flaw.<br /><br />Sludge isn't necessarily related to thermal break-down of the oil. Plain and simple, sludge is caused by contaminates. Modern detergent oils (dino or synthetic) suspend the contaminates so they don't settle onto the engine, forming sludge. When the oil becomes saturated with contaminate particles, new particles settle out of the oil and on to the engine parts, and form the sludge. <br /><br />Synthetics don't prevent the contaminates from forming, however they my marginally suspend more contaminate particles, but not enough to prolong change intervals much. This is why it is important to follow the engine makers change interval, regardless of the oil used (or at least install a bypass filtrations system to help). IMO, any benefits of using a synthetic oil which may suspend more contaminates, is lost by extending the drain interval. Six of one, half a dozen of the other.<br /><br />IMO, the reason you see more sludge around the valve springs and valleys is because, as you say, the oil doesn't move much there. And these are prime spots for the contaminates, which can't remain suspended in the oil, to settle out. I don't believe it's a temperature issue, however I will acknowledge that excessive temperatures on oil can deplete the detergents and additives in any oil quicker. But engines, their specified change intervals, and modern oils have virtually eliminated sludge concerns.<br /><br />BTW, if you want to split sludge hairs, I would recommend staying away from naphthenic-based oils, which are more likely to form sludge due to their lower breakdown resistance. I can't remember the last time I saw one of those though.
