Schaeffer doesn't push their full synthetic very much. I think internal testing has shown that for most applications, it isn't much if any more effective at protecting engines than their Supreme 7000 blend.
I tend to agree. In order to make it worth your while to use a 100% synthetic over a
good blend, you have to push your drain interval. For intervals up to (and even exceeding) 5,000 miles, the blend is perfectly up to the job and protects components no less than a full synth.
I know I am not terribly comfortable pushing an oil change much past 7,000 miles, regardless of brand or oil type. The dark color, the possibility that it could begin to shed suspended particulates in the form of sludge and deposits ... it's just not worth it to me. I'll keep my changes at and around the 5K mark ... and for that, the Schaeffer blends make perfect sense. They are very cost-effective at this point and I don't think I'm gonna get better protection with anything else at any price.
The only exception to this is the coldest winter months. This winter I'll be running Red Line 5W30 from early December through March or April. That'll be 6,000 - 7,000 miles. I had some on hand so why not? Next winter, I'm not sure what I'll use ... German Castrol Syntec? Chevron synthetic??
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Bror Jace