Bud

You can change to a synthetic at any time. NEVER overfill the crankcase. Too much oil can result in frothing of the oil. Don't use Fram filters. They are about the worst filter you can use. Toyota filters are not the best but better than Fram. Not all Mobil 1 oils are true synthetics even if they are claimed to be. When Castrol got away with using petroleum bases on oils they called synthetic, Mobil started using cheaper bases on their 30 weights to compete (5W-30, 10W-30, etc). 0W-40 and 15W-50 Mobil 1 are still made with synthetic bases. Mercedes specifies Mobil 1 0W-40 or 15W-50 but specifically does not approve the use of any of the 30 weight Mobil 1 oils. The gelling/sludging of oil in Toyota/Lexus V6 engines was caused by a change Toyota made to increase the temperatures in the heads of these engines. This was done to reduce emissions. This change resulted in the heads having too big a temperature differential with the block and the hot oil from the head gelled when it hit the cooler block. Frequent oil changes or the use of a true synthetic oil would have avoided the problem. Toyota made a production change to open up the oil passages in the heads to reduce temperatures (although they claim it shouldn't be a problem).