The pan on my auto had a mag already in it from the factory.
I work for a Goulds pump distributor and we have Mag drive pumps that use very strong magnets, some of the high temp pumps (3296) have Sumarian Cobalt magnets which are made for high temps.
I have a bunch of old ones stuck to just about everything in my garage, on my Jeep and truck, could even stick a small child to one if they are getting in the way. Once i was workin on one of the pumps and got my wallet too close and when i went to use my debit card it wouldn't work, ruined every card in my wallet.

 

I use them and I love them. I have 2 back-to-back on my PTO cover filter on the NV4500. I think they are 1½ x 1½ x 3/8. I saw the inside of the filter, and they certainly catch the metal. If you are working with a wrench around them, the magnets will grab it out of you hand and scare the heck out of ya.

A strong buy.

 

 

I use a pair of rare earth magnets to pull my gooseneck trailer. One in a bracket mounted in the bed, the other mounted in the neck of the trailer. The one in the bed can be rotated to reverse polarity. It makes it really fast to hook and unhook the trailer. It is also really great when passing people up in the mountains. Sometimes there isn't enough room to get the truck and trailer both by the vehicle I'm passing. I will rotate the magnate with the switch in the cab till the trailer unhooks, then as I move away to pass I rotate it part way back to pull the trailer back near the car i just passed. Then when I get unough room i pull back in the other lane and turn the magnet on full and suck the trailer up behind me.

 

I've been using rare earth magnets for awhile also. I purchased the high temp kind for use on the oil pan and filter. Also put a few on the front and rear diff, even though they already have em'

 

Dang, I thought I was the only one doing that.
I had to go wireless for the trailer brakes though and use a large magnet with the pole reversed to keep the gooseneck off the ground when disconnected.