After a 110-stop Friday, I found a light amber drop on the cardboard I slide under the front subframe — engine oil or brake fluid, and what’s your quick tell for coolant vs trans fluid on the ground? I wrench on my own car and go by color/smell to triage fast, but I want to compare notes.
On the cardboard under the subframe, I do a quick water-drop test: drip a little water on the spot — if it spreads and thins, you’re looking at coolant or brake fluid; if it beads, it’s engine oil/ATF. For a “light amber drop” I’d then finger-rub and sniff — old ATF can go straw-amber and has that varnish smell — but wet pavement can fake the spread test; did it feel dry-slick like brake fluid?
After that “110-stop Friday”, dab onto a white napkin — coolant wicks a halo, ATF stays centered; colors lie sometimes.
I go by feel — rub a fingertip in it, then rinse under water: coolant goes from slick to squeaky and smells a bit like “maple syrup,” engine oil stays slippery, and trans fluid feels thinner with a detergent tang. @nwilli63 your halo trick pairs well with this rinse test.
Quick tell I use is a $5 UV keychain light — coolant usually glows yellow‑green and dries with a crusty ring, while ATF keeps a reddish tint and stays glossy; dyes can mislead, but the glow rarely does. No UV? Circle the drip with chalk and check in an hour: glycol gets a bit tacky as it dries, trans stays slick. @white25, ever notice the mini rave when a radiator weeps?