Whenever I look at a used car or truck, I looking over the car - truck as mentioned here.Then I pop the hood. I look at all the fluids. Trans should be red and not smell burnt, unless it is a manual trans. The radiator should have green or red fluid, not rust. The engine oil should be brownish, not dark black, or gray. The power steering fluid, should be yellow, or red. After that, I have whoever comes with me, watch the tail pipe when I start the engine. No smoke is good. After it runs for a few seconds, I rev it to 1200 to 1500 RPMs and listing for knocks. Then to 2500, 3500 RPMs. Not holding any of the revs for long. All the while my helper is watching the tail pipe for smoke. When driving the car - truck, I press the brakes to load the engine in each gear while pressing the gas. No need to hold for long, just long enough to see if the trans is slipping, and the engine is taking the load. A few seconds is all you need. The more I can find wrong with it, the better price I can buy it for, if there is nothing major.