OldShooter
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
@HarveyS, I am still waiting for your data to back up this assertion.... The filter is usually the weakest link.
And, while you're at it please provide some backup for this statement.... a cheap filter that can break down ...
Lots of people feel this way and it is an attractive argument, but it is based on a false premise: That frequent new filters offer more protection to the engine. This is not the case.I've always changed the filter when the oil was changed. Oil & filters are cheap, engine overhaul/replacement is expensive.
Inside an oil filter (at least all of the many I have examined) is a bunch of paper-like filter material. It is folded into pleats (to maximize collection area) and arranged around a metal core. Viewed from the top, it looks like a many-pointed star. The purpose of this material is to collect particles that would otherwise be circulating in the oil. Usually there are few particles, particularly with modern engines. If something is coming apart, there will be metal, but that is not what we are talking about here. (Incidentally, every time I have had an engine coming apart I have also seen a very obvious metallic sheen in the drained oil. Watch for it.) As the pleated material collects debris it will offer more and more resistance to flow. In the extremely unlikely event that this gets serious, a bypass valve in the filter opens and lets unfiltered oil pass. The theory is that the bearings will be happier with dirty oil than with no oil at all. But regardless, this is the beginning of the end.
So ... until the filter collects enough debris to cause a meaningful pressure drop, it really doesn't need to be changed and changing it provides no advantage in engine life. (IIIRC some hydraulic systems actually measure this pressure drop as a maintenance indicator.)
I'm not going to wade too deeply into the topic of synthetic oil, except to point out that oil serves two basic purposes: lubrication and collection of contaminants like nasty acids that are the byproduct of combustion. The main purpose of oil changes is to get rid of what the oil has collected. Some of this stuff gets evaporated when the engine runs at temperature; this is why oil change intervals are specified both in time and in miles. The theory is that someone who takes many short trips with the engine often not running at full temperature will accumulate corrosive chemicals quickly even though he/she never accumulates the miles. So he/she should change at calendar intervals. I have never seen an argument that synthetic oil is any different than mineral oil in performing this important function. For lubrication, though, synthetic has some advantage in viscosity at low temperatures. It also is less prone to breaking down at high temperatures; modern cars tend to run at higher temperatures to achieve very marginal improvements in volumetric efficiency.