Regarding Finklejag's original question, does anybody think that moving from Washington (sea level?) to Colorado (5,000+ ft?) has any impact on mileage? Does relative (or absolute) humidity have any effect on combustion efficiency & mpg?
simpleguy_68,
The short answer: swapping in a new filter now would easily take her out to 10,000 miles. I'd do one of three things if this Corolla were my car:
1) Assume that I used GC 'cuz it's as good as everyone says, so there should be no problem going a minimum of 10,000 miles on it.
2) Assume everyone's blowing smoke out their butts & switch to an oil I know can go that long, like Mobil 1.
3) Switch her over to a high-quality HDMO year-round, & get her onto 5,000 mile oil & filter changes for around $10/change.
Now, there are a few unknowns, like how much oil does the car hold, & is her commute a straight shot for 30 mi or is a lot of it in stop-&-go city traffic? Those answers might trend the GC changes down towards 10k mi rather than up towards 20k mi. Another plan might be to wait until 10k mi, then swap in a new filter, top up with more GC & go on to 15k. But this oil's too expensive (& too hyped here on BITOG) to use for only 8k mi intervals.
pscholte,
So what's the deal with GC? Is it truly some wunder brauen, or is it simply a pretender to the throne? Any good Group III oil should go 8k mi in a decent N/A engine.