Well, started by rinsing it from the inside to the outside with warm water. Got a bit of the easier stuff out - small vegetable matter, some feathers, etc. Then dunked it into a bucket of warm soapy water (dawn liquid) for 30 mins with gentl agitation. Pouring this out, I was amazed as the amount of fine black stuff that came out. Repeated this twice and on the last rinse not much more came out. So, its drying now. One bummer is that the pleats did not hold their shape well and many have become wavy or wobbly in appearance. Using the water, I could move them back and forth, so I straightened them up a bit. Now, the filter is drying, so it could take up to a day as nothing more will drip out of it, though I can feel at least a pound of water is trapped in there. CDan and I suspect this was not a Toyota unit, so a proper OEM might tolerate cleaning better. My hope that it would be servicable again are dashed. Pleat displacement has left ares that would get high flow for a while, then plug before having filtration take place broadly across it's media surface. But I'll keep it on hand in the event Mt. Rainier blows and we get caught by the ash plume before getting the loaded 80 out of town. This area got over a foot of ash from St. Helens and people tell me an air filter would quickly clog. So it would at least get us out of town and heading East ahead of the plume. DougM (fessing up the REAL reason he wants a back-up air filter.