Oil filter revisited

[Huskymaniac]

Here are the results based on some data and some estimates gathered from the service manual and oil filter data. The oil assumed was a generic, but high quality, 5W30 oil. The filter assumed was an oversized Purolator P1 or equivalent. Pressure and flow were calculated for 0C and 80C oil temperatures. Three different bypass pressures were used for the oil filter.

In the first plot you have the oil pressure (filter plus engine) and oil flow at 80C. The oil pressure never exceeds the maximum pump pressure so the flow shown is full flow as specified for our oil pump. Since the filter differential pressure never exceeds even the lowest bypass pressure, there is only one curve for pressure and flow. The second plot shows what happens at 0C. Notice that the pressure is above the maximum pump pressure at all RPMs, regardless of bypass pressure. The result is a greatly reduced flow which is well below the design flow rate for the pump. Compare to the first plot. Also, the filters do go into bypass at 0C. The only difference is at what RPMs they go into bypass. The result is that the filter which bypasses at a lower pressure will result in a higher flow rate. But you can see how minor that impact is. It is much less important than the oil temperature. The last plot compares oil flow for 0C and 80C. I had to use a log scale to even make it look reasonable. Each horizontal grid line represents a 10X increase in flow rate. Clearly the engine is starved for oil at low temperatures! I am going to re-do this for a 0W40 oil I am toying with using.

[svxfiles]

So, Tony,
If I want a bigger,
high quality oil filter on an SVX,
that never gets driven hard
untill its warm,
and has a budget,
what do you recommend?

[Huskymaniac]

Originally Posted by svxfiles

So, Tony,
If I want a bigger,
high quality oil filter on an SVX,
that never gets driven hard
untill its warm,
and has a budget,
what do you recommend?

I still think the Bosch 72158 is the best way to go. It is oversized and basically the same as the Purolator Pure One. The non-oversized Royal Purple 10-2808 filter may be an even better option but it is probably more expensive. Hell, the Bosch isn't exactly cheap. You could just stay with the basic Purolator you have been running. It doesn't filter as well as a Pure One but maybe I am just anal about filters and oil.

What I am thinking is that oil choice may be more critical for people that run in cold climates. I have been looking at some options. I know a lot of people like Rotella T6. It is a good choice from the standpoint of being good at high temperature, high stress conditions. That is good for an engine with turbos or with bearings with tight tolerances. The problem with the Rotella is that it is quite thick at low temperatures. M1 0W40, as an example, flows 20% better at 40C, 33% better at 0C and 52% better at -30C. You will get more oild to the engine, faster. Now, the M1 0W40 has an HTHS rating of 3.8 versus the 4.0 of the T6 but the euro car companies have a spec on HTHS for engine wear protection and it is 3.5. So, both oils meet it.

If someone was really concerned about their bearings and wanted an oil with an HTHS rating of 4.0 they could go with Redline 0W40 instead of the Rotella T6. The Redline 0W40 will flow 4% better at 40C, 18% better at 0C and 41% better at -30C. And it will still have an HTHS of 4.0. In addition, it uses an ester base which is really good for keeping good seals in good condition. And, it also has a ton of Molybdenum in it which coats metal parts and reduces wear on startup. This is good for minimizing that Subaru "tick". It is similar to John putting the Lubegard additive into the M1 0W40.

What I am leaning toward is shooting for an oil which just barely meets that euro HTHS spec of 3.5. That will probably be sufficient for bearing protection but it will flow much better at lower temperatures and it should slightly improve gas mileage. As I mentioned before, Acura is moving all the way to synthetic 0W20 oils as a way to squeeze out an extra MPG for CAFE regulations. But those oils do not have an HTHS of 3.5 and concern me from a wear perspective. So you have one camp that wants super thick oils for maximum engine protection and another that is pushing for thinner oils for better gas mileage and HP. I feel, shooting for an HTHS of 3.5 with the highest possible viscosity index is the best compromise. A high VI will give you the best possible low temperature flow for a given HTHS.

No surprise, but I did that analysis. The end result is a blend of Redline 0W40 and Redline 0W20. For an SVX with an oversized filter one would want 3 quarts of 0W20 and 4ish quarts of 0W40. The end result is a beefy 0W30. The HTHS is about 3.5 and, relative to the Rotella T6 will flow 37% better at 40C, 54% better at 0C and 75% better at -30C. And, again, you get lots of esters and molybdenum. Sadly, it would be quite expensive. If someone wishes to go that route, I would seriously suggest going with the Royal Purple filter and extending their OCI to at least 7500 miles to make it somewhat affordable.

With my blend of M1 5W30 HM and M1 0W40 I also get the magical HTHS of 3.5 but with slightly degraded flow relative to the Redline products. I am using the Bosch filter. For simplicity I really like the 6000 mile OCI I am using so I probably won't go to the more expensive Redline/Royal Purple combination on the SVX. On the new Acura, however, I am doing just that. The car tells you when to change the oil and it comes between 7500 and 8500 miles for most people. By the way, I am loving the 6MT and 270HP engine. Damn that car is smooth. I am getting 33MPG on the highway and 23MPG in the city. And, as far as I know, it still has the original plugs at 114K miles!!! I just hope there hasn't been too much wear by running that water thin Honda oil for all those miles.

[svxfiles]

PM sending;

[Huskymaniac]

Update:

The Bosch Premium 72158 is no longer available nor is the Mobil 1 M1-401 filter that was cross-referenced to the oversized L30165. For oversized filters, our options are decreasing. I am now going to use either the Purolator L30165 or the K&N HP-4001. The Mann filter is also a decent choice but not as good as the Purolator or K&N. The Purolator and Mann flow a little better but the K&N filters a little better. Flow only matters when revving high which should only be done when the oil is up to temperature. And if you plan on revving high and under high throttle, a really high flow filter might be in order like the one from Royal Purple. But that isn't oversized and it is expensive. For everyday driving, I think our best option is now the K&N "oversized" filter. And the good news is that it is currently cheaper on Amazon than the Purolator L30165. I just bought 6 of them.

[bwb3]

I have been using the L30165 Purolator (Porsche part). Stopped by O'Rielly Auto Parts. They didn't have the Purolator instead, WIX Filters #51287. I hope it is just as good, label says made by Affinia in North Carolina, USA.