: High risk, but high reward for those who know how to spot a runner quickly. Conclusion

: Pull the oil dipstick; if the oil looks like chocolate milk, the head gasket is blown—walk away. If the transmission fluid smells burnt, the gearbox is failing.

: If the Check Engine Light is on, use a cheap OBD-II scanner to see why. Some codes are simple (gas cap), while others (catalytic converter) will cost more than the car is worth to fix. Where to Shop