I have the same car, but mine is an '03, purchased in March of that year. Nissan recommends mineral oils but I think manufacturers have their heads up their @$$e$ when they make mineral vs. synthetic recommendations.
My car's maintenance history has been a mess of overly-frequent oil changes due to freebies from the dealership (some connected to engine recalls) and my own anal-retentive compulsiveness.
However, this past April (at around the 17,600 mile mark) I dumped the Red Line 5W-30 I was using all winter and began using Schaeffer Supreme 7000 synthetic blend in 5W-30. A real Group II+ & PAO blend with a great additive package. I also changed out the crappy OEM Nissan air filter which was both warped and very dirty for a Purolator element.
My mileage, which had consistently averaged 28.3mpg during my first year of ownership, instantly jumped to an average of 31mpg.
I think four factors weighed in: The engine had finally (fully) broken in, the new air filter, the newer oil and the warmer ambient temps.
I'll be doing a UOA on this batch in a few weeks (I'll post results here in mid-August) and we'll see if this stuff sheared down any. Since the mileage boost was immediate and it hasn't changed throughout the interval, I seriously doubt it.
And after around 4,000 miles to date, I just checked the level on the dipstick and it hasn't budged from the full mark.
If I were in Florida, I'd run the same brand of oil, only in 10W-30 weight. If you live in Florida where it
occasionally gets down near the freezing mark, you
could switch to 5W-30 for the coldest months ... although I think that's just being extra picky. But then again, we
are at BITOG.
How about Exxon Superflo for your motor? That's a good question. Only a UOA will show you how this stuff is doing in your QR25DE. Of course,
any SL oil will be OK for modest (3,000 mile) oil change intervals.
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Bror Jace