I've been very lucky on my last five of 6 used car purchases, an 84 240D, an 85 300D,an 87 300D, 91 Volvo, an 86 Corolla, and a 95 SAAB ..
On the unlucky choice, my 240D, which had a bad engine, I was lucky because it led me to Shop Forum.
On all of those cars, I did do a thirty minute visual inspection and a test drive, but I did not do compression tests, high speed driving /braking tests, or any prolonged technical inspection.

Thats not too say I'm lazy, over confident or naive. I think the reason I bought those five vehicles was based on instinct, and I wonder whether any of you do the same? I'll bet more of us use Instinct to buy used cars than we think.
Instinct is hard to define, but I guess some of it is based on our judgement of the owner and our feelings about the car and then you throw in things like how much you have slept and ho much coffee you have drank.(Too much coffee would lead to incorrect instinct.) I'm wondering whether my continued use of Instinct in buying used Diesels or cars in general is valid and whatyou feel about it.
( In my case, I'm surprised I didn't make more mistakes, because I am very naive. )