Well there's many variables to this topic. Such as warranty concerns, oil life doesn't neccesarily relate to filter life, etc... And I've never really been a member of the club that thinks oil sitting in my engine while the car is in the garage, is the same as oil being used while driving in the city and highway. But I will say my Z is an exception to my normal synthetic rules. In a former career I've met with Mobil engineers in the early 1990's. Before synthetic was as popular as it is now and before such things as "high mileage" and "extended performance" versions. Back when Mobil 1 was just Mobil 1. And people didn't feel the need to spend $3 for a qt of synthetic because a qt of crude was .80 cents. But even back then the engineers would tell me that mobil 1 was designed for 15K to 30K of life between changes. Their problem was in legalities in making such allegations. Would people change their filters more often or expect a filter to last 15K+ miles? With that said, all my vehicles (even motorcycles) run Mobil 1. In every car but my Z, I have a twice a year change rule. I don't pay attention to mileage, I change the oil before the winter months and change it again before the summer months. This includes a Durango Hemi that I bought new and now has 200K miles on it that runs great. Now the Z on the other hand with it's high tolerances and 5W oil that seems to evaporate like water gets a change about every 5K miles. But like I said because it's still in warranty, I'm a little more anal about it. Plus that little thimble size oil filter can't collect much before flow starts restricting. People need to do some research on synthetics before thinking their only gain is lubrication. If they did this, no one would buy crude ever again for their vehicles.
Crude is natural product pumped from the earth. No amount of refining can eliminate the waxs and varnishes within it. Synthetics don't contain any waxs or varnishes - Thus with crude you create sludge
Since it's a natural product, crude is made up of several different and varying molecules. Sythetic is preformed in a lab and all molecules are the same size - Thus lubrication is far superior
Thermal breakdown of crude occurs right around the normal operating temperatures of your engine, about 250 degrees. Synthetic breakdown doesn't occur until above 400 degrees. Along with cold viscosity, the cold operating temperature of synthetic is much lower than crude. Where crude loses it's effectiveness around +10 to +20 degrees, synthetics are good to -20 to -30 degrees.
Hope this helps
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