How many people does it take to make something said a fact? When it comes to believing synthetic oil actually cleans engine deposits so well the engines develop leaks, well I haven't seen enough documented proof to believe it. I'm not saying that it doesn't or couldn't happen, but I think coincidence also plays a big part in this. You get several dozen people making this claim on the net and suddenly it becomes fact. With that said here’s what I think.
Three of the main advantages of synthetic oils, and there’s more, have over conventional oils are: 1. Its superior flow characteristics at very low temperatures. 2. Its superior ability to withstand extreme engine temperatures. 3. Its superior lubricating qualities. Do you live where the temperatures get very cold in the winter? I’m talking below 0 for long periods. Is the engine turbocharged, in your case, no? How slippery is slippery enough for normal everyday use? Conventional oil has been around for over 100 years and has been refined and improved along the way. Racers use synthetic oils because their engines see extreme running conditions and because synthetics have been documented to reduce drag on moving parts which frees up power.
My wife’s Catera has 122k miles on it and I change the oil every 5k miles with conventional oil. Even after several thousand miles after an oil change, the oil on the dipstick remains very clean looking. I’ll never switch to synthetic in her car. Your car has accumulated 103k miles on it using conventional oil with regular oil changes. The engine was designed to be used with conventional oil by highly trained Japanese engineers. If changing to synthetic oil makes you feel better, and there’s something to be said for piece of mind, do it. I also highly believe in the saying, “If it isn’t broke, don’t fix it.�