I am huge on the brake and coolant test strips, but be careful…
I always checked history on a customers vehicle to see prior recommendations as well as the maintenance history… I have worked with great mechanics that I would trust anything they said that a vehicle needed but I always did random shop checks just to keep them on there toes as well as always double checked the mechanics that seemed to rubber stamp the WO’s…
Anyway, we got a new batch of coolant test strips and I noticed a lot of guys that didn’t normally recommend coolant flushes had recommended them even on vehicles that I wouldn’t think would need them and it threw up a red flag to me, not hard to do lol, so I did recommend a few mileage only based flushes and informed the customer that I didn’t see any issues and that the coolant looked good so they may have had it done elsewhere, then I got one from a very trusted mechanic that brought me the test strip (as most did) and said it failed but the coolant looked great, I checked history and the same mechanic had just flushed it last service… So I checked our new coolant in the 150 gallonish tank and it failed, so I said don’t use that coolant and so I ordered a few different gallons and makes of coolant from a few different parts houses and tested them and they failed… So I went over to a guys box that hardly every used them cause I new he had some old ones and ALL the new coolant we had checked out great even the few vehicles that were still there that had thrown a red flag up…
Bottom line is, always check your new strips against known new coolant, as I had to throw away thousands of new test strips as well as inform corp to send out an email for the other shops… But that was the only time that happened…