Aftermarket fuel filters

[Mr Mower Man]

Can anyone explain to me how an aftermarket fuel filter can claim to be a replacement for an OEM filter when the micron ratings don't match? Take the Briggs & Stratton 691035 filter, for instance. It has a 40 micron rating. The Stens aftermarket replacement (120-562) is rated at 30 microns, Rotary's (7998) is rated at 60 microns, and Oregon's (07-107) is rated at 80 microns. Am I really using an aftermarket equivalent with one of these filters? Or does it really not even matter?

Furthermore, is a paper filter with a 75 micron rating any more or less effective than a screen filter with the same micron rating (like the Briggs & Stratton 394358S)? It seems to me that a paper filter would be superior to a screen filter, though I don't really have any data to back that up. Or, again, does it really not matter?

Thanks

[bgsengine]

Can anyone explain to me how an aftermarket fuel filter can claim to be a replacement for an OEM filter when the micron ratings don't match? Take the Briggs & Stratton 691035 filter, for instance. It has a 40 micron rating. The Stens aftermarket replacement (120-562) is rated at 30 microns, Rotary's (7998) is rated at 60 microns, and Oregon's (07-107) is rated at 80 microns. Am I really using an aftermarket equivalent with one of these filters? Or does it really not even matter?

Furthermore, is a paper filter with a 75 micron rating any more or less effective than a screen filter with the same micron rating (like the Briggs & Stratton 394358S)? It seems to me that a paper filter would be superior to a screen filter, though I don't really have any data to back that up. Or, again, does it really not matter?

Thanks

Micron rating is just that - the smallest particle , measured in microns (A micron is a unit of length equal to one millionth of a meter) that will pass through the filter media.

So a 60 microns filter will block particles that would pass through a 75 micron filter - media does not matter whether it be screen or paper - micron rating will be the difference. Many of the aftermarket parts do not have a guaranteed micron rating - they will often be typographical errors, or they are "certified" by the manufacturer (from china) and the vendor just takes the manufacturer's word for it - manufacturing changes may result in different micron ratings but the brand may be using an old rating from a different supplier.. lots of variables.

Considering this: 40 microns is 0.001575 inches 60 microns is 0.00236 inches , 75 microns is 0.00295 inches and 150 microns is 0.00590 inches

Do you think you could even SEE a piece of dirt that is .0015" diameter suspended in a gallon of gas?

Micron ratings are specified so that any debris that does manage to pass through won't clog the smallest port or jet in the fuel system - if you put in a 75 micron filter where a 60 micron is specified, eventually you'll end up with a clogged carburetor. At the same time, a smaller micron rating can also affect fuel flow (read: gravity feed carburetors) so putting a finer micron rating filter in a system where a coarser rating is specified can affect fuel flow in the system.

So, we'll use OEM product wherever we can but if we have to put in an aftermarket filter somewhere, we'll use something that is at least close to the original rating, if we have any specification available, failing that we'll put in a filter between 60-75 microns

[tomw]

I would only emphasize that you want to select a filter that meets the application of gravity flow or pressurized. A gravity flow system would need a 'looser' (larger micron) filter than a pump system because the pressure developed is dependent on height and fuel level in the tank. A pressure system can force fuel through a smaller aperature and does not depend on height nor tank fuel level.
It was in the reply, but worded a bit different. In short, be sure to note whether the filter is for a pressure or gravity system.
tom

[Mek-a-nik]

I would only emphasize that you want to select a filter that meets the application of gravity flow or pressurized. A gravity flow system would need a 'looser' (larger micron) filter than a pump system because the pressure developed is dependent on height and fuel level in the tank. A pressure system can force fuel through a smaller aperature and does not depend on height nor tank fuel level.
It was in the reply, but worded a bit different. In short, be sure to note whether the filter is for a pressure or gravity system.
tom

Welcome to the forum, Tom.
I used to be careful about pressure vs. gravity filters, too. But I've seen plenty Craftsman, (or AYP), lawn tractors with B&S engines that have a gravity system (red filter) but have a pressure filter (white filter) installed. Machines that have never been serviced before.
Beats me.

[bgsengine]

Welcome to the forum, Tom.
I used to be careful about pressure vs. gravity filters, too. But I've seen plenty Craftsman, (or AYP), lawn tractors with B&S engines that have a gravity system (red filter) but have a pressure filter (white filter) installed. Machines that have never been serviced before.
Beats me.

Acrually the color is not proof of micron rating - MTD's OEM filter for the same 150 microns is white but looks identical to the briggs 75 micron filter - and many aftermarket filters do not make that distinction either - color is not a proving factor You'd have to cut the filter apart and inspect the element to be sure

[KE4AVB]

I must be really lucky here I have installing 25 micron (Stens 120-436) filters on those riding mowers with gravity feed systems for several years without problems. It the small push that I am install those pancakes on mostly because they coming in without any filters.

[Skywatcher]

Greetings All

Where I live, quite a few farmers use truck mounted crop sprayers powered by various makes of engine. Although the Honda engines have the in-tank fuel strainer and some of the brand-B engines are factory fitted with the 150 micron filters, it's not unusual to find a layer of really fine silt in the bottom of the float bowl. Even though this silt is fine enough to pass through the filter, it still plugs the main jet when the silt layer gets more than ½" thick. I've found that the Stens 120-436 filter works on equipment where the fuel tank is more than 6" above the carburetor, for machines with less fuel head height, I prefer Stens 120-562 as it seems to give less flow resistance. On machines where the bottom of the tank is the same height as the carburetor (gravity fed), a pancake strainer like Stens 120-014 is usually the only option.

The only place I use a 150 micron strainer is between the fuel tank and the fuel pump, then put a paper element filter between the pump and the carburetor too much flow restriction on lower fuel tanks. When installing a paper element filter (Stens 120-436) it should be installed that the dirt accumulates outside the element so you can see when it's dirty. If the dirt accumulates inside the element, you have no way of knowing how dirty the filter is until the engine starves for fuel and quits. All the best,

Sky

[KE4AVB]

Stens 120-436

• Stepped fittings for both 1/4' ID and 5/16" ID Fuel lines
• 23-28 Micron
• Overall length longer than 120-562

Stens 120-562

• 1/4" ID Fuel Lines only
• 30 Micron
• Overall shorter than 120-436

Both filters have flow direction marked.