Rick's Free Auto Repair Advice

Best Oil filter

Who makes the best oil filter?

If you’re here it’s because you’re looking for help in buying the best oil filter. Maybe you’ve already looked at a few oil filter reviews and “studies” already. But it you put any stock on those supposed studies, I’ve got some land in Florida I’d like to sell you. None of those “studies” are worth the paper or pixels they’re written on. They simply don’t duplicate real life engine conditions. You can read my take on those bogus studies here.

Oil filter media is application specific and that’s far more important than brand

The first oil filters used steel wool, wire mesh, screens, and felt. The next generation moved on to cotton and other fabrics. Then came disposable filters made from cellulose. Before synthetic oil and extended oil change intervals were around, manufacturers used only 8 different types of cellulose papers . Then things changed.

Keep that in mind as you review the numerous oil filter reviews and “studies,” because most are woefully outdated. Because, the filter media used in the test filters may not be the same media the manufacturer uses for the filter for YOUR vehicle. You simply can’t interpolate good test results from a part number to reflect the overall effectiveness of the entire brand. Keep in mind that manufacturers build their filters to match the needs of a particular engine.

Economy, OEM and premium oil filters

A high quality oil filter is built from quality components. First, it must have a quality filter media. Most economy filters are made with cellulose that’s only about 80% efficient. But a multi-layered premium filter is made with cellulose and synthetic glass fibers that are 99% efficient. That extra filtration traps more harmful particles and sludge. Next, the filter must have enough surface area to keep filtering for the full life of your oil change. Most people think that means a larder size filter or a filter that’s packed with more pleats — not true!

Again, this comes back to the filter media’s composition and efficiency. Some filters made with synthetic filter media can last far longer than a conventional filter twice the size.

Aside from the filtering media, the differences are in the filter pleat support, bypass valve, anti-drainback valve and end cap design and construction. Economy filters, (like the one shown here) have a plastic core best oil filter brandtube that only partially supports the filter media. The premium quality filter, on the other hand, has a metal mesh core support to reinforce every pleat.

oil filter media

A bypass valve opens during periods of high pressure. It allows oil to bypass the filter media and drain down the core tube. Because if the filter media gets totally plugged, the oil pressure can destroy the tin can. Some car makers install a bypass valve in the oil pump, so those filters don’t need the valve. The economy filter shown above skipped the traditional metal spring-loaded bypass valve and relies
instead on a combination anti-drainback/bypass valve. The rubber valve collapses during high pressure cycles. That allows the oil to drain down the center tube as well.

Finally, the filter must have some type of anti-drainback valve to prevent

cut away views of oi filters

Economy oil filter with nitrile anti-drainback valve versuse a premium filter with a silicone anti-drainback valve

dry startups on vehicles where the filter is mounted on its side or at an angle. Economy filters use a Nitrile valve that can harden and crack after 3,000 miles. Premium filters use a silicone anti-drainback valve that can last the entire length of an extended oil change (7-10,000 miles). It’s easy to tell the difference between the two materials—nitrile is black. Silicone is either orange or light gray. You won’t find silicone valves on economy filters—they just can’t afford to use those costlier materials.

Oil filter dirt holding capacity specs are a red herring—kinda

Engine oil filters must do these three things well:

1) Remove the size of contaminant considered to be most detrimental to that particular engine. This is based on engine material design and clearances, so it’s different for every engine.

2) Have enough contaminant holding capacity to last the recommended service interval.

3) Provide contaminant capture yet allow oil flow as required oil pressure specs, even at cold temps.

Those requirements can create contradictions. For example, a filter that captures smaller particle sizes may also restrict oil flow at cold temps. In addition to restricting oil flow, it may clog faster and go into bypass mode where it stops filtering completely.

Engine Contaminant discussion

So before we even talk about contaminate capacity we have to understand what it is. There is dirt, and then there’s dust. Most people think engine contaminants come into the engine from outside. Not true.

Think about how dirt can enter an engine. It can come through the air filter and into the intake. Any dirt that gets past the air filter is going to go into the combustion chamber, not your oil pan. Yes, some dirt could possibly move into the pan via piston ring blowby. Most likely though it’ll be burned during combustion. Besides, preventing dirt entry into the cylinder is the air filter’s job, not the oil filter.

Dirt can also get pulled into the crankcase via the positive crankcase ventilation system. The intake is constantly sucking blowby gasses out of the crankcase. That air has to be replaced or the crankcase would be running a negative pressure. But the replacement air is coming from the intake duct after the air filter. So any street dirt that gets into the oil got there because of a problem with the AIR filter or a leak in the air filter box, seal, or duct.

But here’s the key to understanding why street dirt is almost irrelevant. Almost all late model engines monitor intake mass airflow to properly calculate air/fuel mixtures. A leak in the intake air duct, a leak that could introduce dirt into the crankcase, would also cause a drivability problem. An air duct leak letss in UNMETERED air. The PCM sees a lean condition caused by the leak and adds fuel to compensate. So you get a high idle speed and poor gas mileage.

Bottom line: The air intake systems on late model cars are sealed much better than the systems used on carbureted engines.

Sludge is really your engine’s #1 enemy

This is what sludge looks like on an oil filter

Sludge is caused by oil, soot, water, viscosity improver breakdown, and

oil filter caked with oil sludge

This is what sludge looks like on an oil filter

acids from combustion blowby gasses. The oil filter’s ability to trap sludge is FAR more important than its ability to trap dirt (yes, it’s important to trap dirt but if your air filter and intake ducts are properly maintained, you won’t get dirt in your engine).

Dust, on the other hand, comes from deteriorated gasket material, residual core sand from the casting, and worn metal. Some filter manufacturers list a dust holding capacity in grams. But as you’ve seen so far, dust is far less of a problem than sludge.

Here are the best ways to create sludge:

Short trips after a cold start—oil doesn’t heat up enough to evaporate excess water, raw gas, and blowby byproducts. Stop the engine and all that liquid mixes with crankcase oil to create sludge.

Pedal to the metal driving

Extending drain intervals beyond the oil’s useful life

Driving while low on oil

Driving in hot conditions

Viscosity improvers are polymeric additives that uncoil to “thicken” oil at higher temperatures—like adding flour to thicken gravy (except the coils contract again when cold). Unfortunately, these coils aren’t very good lubricants so they shear (the coils get cut) during periods of high torque and high temp. As the VI shears, it accumulates at the bottom of the crankcase, mixes with water and gas and forms sludge.

Running oil beyond the recommended drain intervals not only damages the VI additives, but exhausts the other additives like dispersants, detergents, anti-corrosion, and anti-forming agents. Also, running your engine when it’s low on oil puts tremendous stress on the remaining oil, causing it to degrade much faster.

Economy versus premium oil filters

Today filter manufacturers use well over 80 different types, and they range from cellulose to synthetic glass, to a combination of both. Cellulose filter media excels at trapping dirt particles. Synthetic media excels at trapping sludge and combustion byproducts. That’s why these filter comparison “studies” are baloney. They simply don’t duplicate real engine conditions. In the latest studies, the authors heat the oil to make it break down. Great. But in order to create sludge you need more than just heat. You also have to introduce combustion byproducts in real world amounts and subject your samples to hundreds of heat/cold cycles. Not a single one of these studies does that (that I’ve seen).

So where does that leave you as a buyer? Well, putting no stock in filter studies for one. Next, understand that all filter manufacturers make several different quality levels, so buying by brand alone doesn’t work.

How to buy the best oil filter

If you’re running conventional oil, have under 100,000 miles on the odometer, drive under the car maker’s severe conditions (as defined in the owner’s manual) and you change your oil according to the manufacturer’s recommended intervals (usually 3,000 miles), you can probably get buy with an inexpensive filter. It’ll most likely be made with cellulose filter media. It’ll most likely have a nitrile (versus silicone) anti-drainback valve. But those are fine because you’ll be changing your oil according to the recommended schedule. If you don’t change your oil and filter according to the manufacturer’s schedule, you darn well better install a better filter.

If you meet all of the above conditions but have a higher mileage vehicle, move up to a better filter. As engines wear, they produce more blowby and that increases your chances of sludge. A higher quality filter will do a better job capturing sludge particles.

If you’re running synthetic oil, buy the best oil filter that’s made with synthetic filter media or a combination of synthetic and cellulose.

The oil filter size issue

I can’t tell you how many times I’ve seen car enthusiasts brag about how they found a larger oil filter for their engine. They’ve convinced themselves that their oil filter now captures more crud. Really? Didn’t you read the part about how filter media is chosen by application? In my discussions with oil filter engineers I’ve witnessed them laughing out loud at this one. Why? Because large filters often have less efficient filter media so they can provide enough flow and less pressure drop. So don’t kid yourself by using a filter other than the model recommended by the manufacturer. You didn’t design the filter. You didn’t design the engine. You simply don’t know what’s inside every filter and the filter manufacturer certainly isn’t going to tell you because it’s a trade secret.

Finally, Rick’s opinion of cardboard oil filter end caps

Every one talks about how Fram used cardboard end caps in their economy filters, as if metal end caps are superior. The entire discussion is simply B.S. and you should put no stock whatsoever in the cardboard versus metal end cap controversy.

The role of the end cap is to prevent oil from bypassing around the ends of the pleats. Filter manufacturers glue the ends of the pleats to an end cap. So the effectiveness of the end cap depends on its ability to bond the pleats to the end cap without allowing oil seepage through the cap or the glue. Nobody actually uses cardboard, not even Fram. Instead they use a resin impregnated fiber board. Resin impregnated means it’s soaked in a plastic resin under pressure to make it impenetrable, get it? The resin impregnated end cap actually seals better to a fibrous pleat than a metal end cap because it’s a resin-to-resin bond. So, if the end cap is impenetrable and it bonds well to the filter media pleats, what’s the issue?

To secure filter media pleats to metal end caps, filter manufacturers have to flood the caps with enough adhesive to prevent the possibility of oil bypass in the event the adhesive breaks away from the metal end cap. I’ve talked one-on-one to the engineers from many oil filter manufacturers. All of them would prefer to use resin impregnated end caps because they cost less, bond better, and actually perform better than metal end caps. But they feel they can’t because of all the marketing hype surrounding metal end caps. So they use metal end caps simply because of marketing.

©, 2015 Rick Muscoplat



Posted on by Rick Muscoplat

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