I want to extend my oil change intervals
I feel it's OK to extend oil change intervals using synthetic oils. There's really no reason to use them unless you can. Regular oils are good and cheap enough for normal change intervals. But, if you use a car in high mileage situation, where combustion by products are not likely to accumulate as much and you do it to compensate for oil break down, then yes. If you're an average miler of 15k to 20k per year but do mostly highway, yes. Stop and goer with frequent engine shut offs like many people do with fewer than average miles per year, than no.
Under ideal, high mileage, heavy highway use, 7500 to 10K mileage intervals are used regularly, and successfully by many agencies. We guys who drool over used police CV as used cars understand the less frequent but successful (10K around here), oil change intervals they have. Your tax dollar and pocket book would want it no other way. I know retired cops who do it now with their own vehicles. They're converts.
It's foolish and a waste of good money, to use synthetics and change oil too frequently (as with any oil type), except in very specific high load circumstances, or very cold weather applications. Frequent oil changes (3K or less) are often way over rated.
Bottom line; how you use your car will help determine whether it's a good idea.