Confused Why Does Changeover Timing to Synthetic Matter

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Jun 17, 2003
I just purchased a new WRX 2004. The only facts I know about it is a that break-in is 1000 miles. The first oil change listed is 3750 miles severe. I already violated the 4000 rpm rule in the manual on the test drive and on occasion now at 75 miles. (its very easy to surpass [I dont know] ). Actually I'm a mellow driver. Anyway are there any facts out there about a switch over and why would it matter? Doesn't synthetic have similar properties to conventional oil just better? I was planning first change at ?????. My main reason for synthetic is the potential of high temps that are generated by the turbo and it "cooking" the oil. I saw a similar thread but was wondering of any written papers or information on the subject? I plan on using Mobil 1 as my trusted mechanic uses it and actually out of bottles. Mobil 1 website says it does not matter in FAQ. Still no idea when to change it out (I imagine at least 1000 miles). The car will sit for three weeks in August as I will be traveling to France. The car will be driven mostly for highway miles. [ July 14, 2004, 04:04 AM: Message edited by: harper ]
Given that synthetics are "slipperier" than conventional motor oils, and that "break-in" is really <i>controlled</i> wear to seat rings to their bores and mill other sliding parts, maybe it would be better to change out the factory-fill oil and filter at about 500 miles to discard left-over machining debris. Use the recommended viscosity range <i>conventional</i> oil at this time, and leave it in until the odometer indicated 3,750 owner's manual recommended 1st oil change point. At that time, if you want to initiate your favorite flavor synthetic (and another new filter), it would be appropriate with the least expense during the initial break-in period.
The current school of thought between the auto manufacturers and the oil companies is that it no longer requires a "break-in" period before using snythetics. Assuming that you believe them ..then the only reason I wouldn't use it is that I'd feel silly wasting expensive oil for the first few thousand miles just getting rid of the break in crap.
I think that 1500 miles minimum up to 5000 miles on the factory break-in oil is a good plan. The mating of the rings to the cylinder wall is most important...and the break-in oil is a constant. Once the engine is warmed up , select one gear higher and do some 10 second full throttle accelerations between 2000 RPM and 4000 RPM, folloed by zero throttle engine braking deacceleration. Do not lug the engine. 10 or 15 cycles like this will help to work the rings and create a good seal. Cehck oil consumption and MPG frequently. Once you see the rate of oil consumption decline,and/or MPG improves... then it is a good time to change to synthetic. IMHO
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