T6 is fully synthetic:
http://www.shell.com/rotella/products.html
I've been using T6 for several years and agree, it performs well in the 6.2
http://www.bobistheoilguy.com/motor-oil-103/
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( Oil Types – Synthetic / Straight varying Thickness )
Let’s look at the make up of synthetic based oils. A 10W-30 synthetic oil is based on a 30 grade oil. This is unlike the counterpart mineral oil based on a 10 grade oil. There is no VI improver needed. The oil is already correct for the normal operating temperature of 212°F. It has a thickness of 10 while you drive to work. It will never thin yet has the same long term problem as the mineral based oil. They both thicken with extended age.
Synthetic oils are derived in the laboratory. They are pure, usually nearly clear. I describe mineral based motor oils as a distilled, concentrated product. The impurities need to be removed from the raw petroleum. These oils are therefore less clean and contain many impurities. Again, the problem is really more of theory than practice but the difference does exist.
People repeatedly say that synthetic oils are more stable in a hot engine. I hear that they lubricate better.
The answer is yes and no. Oil molecules do not break down, just the additives. Generally, the synthetic oils do not have VI improvers so have less to lose.
There are some properties of synthetic oils that actually result in less wear than with mineral oils. These help increase your gas mileage as well. Due to a reduction of internal friction of the synthetic oil your engine will run a bit cooler. Wear increases as temperature increases, all other things being constant.
A main advantage that the synthetic has over the mineral based oil is the ability to lubricate at startup. Both types of oil have the same specifications at 104°F, 212°F and 302°F. It is the startup viscosity characteristics that separate these oils. Synthetic oils do not thicken as much on cooling. They have better fluidity as the temperature drops.
A synthetic oil that is labeled as 10W-30 is less honey like as a mineral based 10W-30 motor oil at startup. They both have a thickness of 10 at normal operating temperatures. At 75°F the synthetic is not as thick. At 32°F the difference between the two is even greater. At 0°F the mineral oil is useless yet the synthetic works fairly well. Just keep the RPM to a minimum.
At temperatures below zero you will not be able to start your car with mineral oils while the synthetic oils may be used to -40° or -50°F. Oils are so thick that the normal method of viscosity measurement is not possible. Instead we measure if the oil can even be pumped or poured. Again, we are only discussing a single category of oil, the multi-grade 10W-30 API / SAE grade."
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