Oiling Foam Filters

[Merkava_4]

Is is completely necessary?

I know Briggs & Stratton says to submerge it in 30 weight and then squeeze out the excess, but it still makes a mess of the air cleaner over the long haul.

[bgsengine]

not if done properly , and no not submerge but you only need enough oil to saturate the foam - Probably a couple teaspoons depending on element size.

Oil is critical to proper operation of the oiled foam filter - a dry filter will not trap finer dust, so putting in the oiled foam element without oiling it is not much worse than no filter at all. (Note- Not all pre-filter elements are oiled - some are, some are not, best to consult repair manuals on that point)

What I always did for them was on a new filter, oil doesn't want to soak in, so I'd pour out a little from the quart and just rub it in across the foam to dampen it and break surface tension, then I could add more oil, squeeze, add oil and squeeze until I started squeezing oil out (after doing it often enough you can just tell by the weight of the filter when you got enough oil) and then squeeze out excess into oil drain pan, wipe hands with a rag, then wrap filter in the rag and squeeze more until I couldn't squeeze out any more oil, at that point, oil film on the filter element tends to stay in place, never had any problems with oil messes dripping off the filter. Alternatively you could buy some of that spray on filter oil (it's like bar oil, it has high-tack additives to it making it sticky) often sold for performance (like K&N) and ATV air filters... but even that if applied to excess can cause the same drippy mess as an air filter that hadn't been completely squeezed of excess oil.

As far as long haul, eventually you might get some drip if the engine were to sit without running for long enough, or not serviced regularly. (air flowing through filter fights against gravity causing oil to drip down)

[creia]

While the foam filter may effectively stop grass clippings or other larger particles and debris, I do not believe that they will do much (If anything) as far as stopping dust. Dust getting into your bore would be abrasive and cause scoring. The oil on the foam will attract the dust particles and hold them. I have always oiled the foam filters in all of my vintage Briggs engines.
Michael

[38racing]

the 691 cu tecumseh vtwin manual specifically says not to oil the prefilter. It's a thin square foam.

[bgsengine]

the 691 cu tecumseh vtwin manual specifically says not to oil the prefilter. It's a thin square foam.

Yeah. foam pre-filters up directly against a paper element is kind of a no-no on oiling... - As a rule of thumb, if I didn't have manual or repair instructions saying otherwise, I look at the pre-filter element and how it sits in relation to the paper primary element.. If the foam sits directly on the paper, don't oil it (oil would soak into the paper) but if the foam and paper are separated by a mesh or other barrier (typically steel or plastic) from the paper itself, then I'd generally lightly oil the foam.