Originally Posted by altiain
Umm... unless you're running a 50-gallon-sized oil filter, a typically oversized filter ain't going to cause low oil pressure problems. :?
However, an oversized oil filter can provide some useful benefits over a stock-sized filter, especially one as dinky as the OEM Miata one. For a car that gets autocrossed, time trialed, or tracked often, I'd definitely recommend a larger filter. Here's a short list of some of the benefits:
1) Larger oil capacity.
2) Better oil cooling due to the larger can surface area.
3) More filter medium, resulting in less oil flow restriction and longer serviceable life.
4) Longer engine oil usage.
Now #4 ain't that important (you do change your oil regularly, don'tcha?), but #1-3 can be important, especially for long autox courses, time trialing, or open track, where the car sees extended high rpm usage. High rpms mean high oil pressure. The higher the oil pressure, the more likely it is that the filter bypass valve opens, in which case the oil is completely unfiltered. Oiling systems have filters for a reason.
Using a larger filter means more filter medium for the oil to pass through, which mean less restriction and less pressure buildup on the "dirty" side of the filter, which means you have a higher likelihood of continued filtration during extended high rpm operation.
Slightly improved oil cooling at the filter and more oil capactiy are both secondary benefits of a larger filter, as both will allow lower oil temperatures during extended high rpm running.
Last, I firmly believe anyone who does autox/time trial/open track owes it to themselves to use full synthetic oil, as it - like the commercials say - better withstands viscosity breakdown at high temperatures.
I typically use Mobil 1 0w40 in my car, along with Mobil 1 filters. I think the OEM Miata size is M1-110, but I use '97-'03 Honda Prelude-sized filters (M1-104 in the Mobil 1 range), as they fit the Miata and are about 1.5 times the size of the OEM filters.
