What has occurred in all these cases is that you did not get the tune-ups that your car needed, and as a result you have wear and breakage of key engine components. It is a case of false economy or failure to take proper care of the car at the proper time.

If a car is using a lot of oil you have one of two situations to handle at once:

1. Oil is leaking out of the engine. The engine is sealed off. However, the seals are made of rubber and they do wear and let oil through. If a seal to the outside of the engine is leaking then you will get oil leaking outside the car. The oil can be seen on the outside of the engine or on your driveway.

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2. You have a leaking seal inside the engine. The lubrication system is designed to move the oil around to the parts that need it but to seal off the oil from going elsewhere. If the seals going into the valves are worn, oil trickles in between the valve and the valve sleeve and it will then trickle down into the cylinder head and burn. If the piston rings are worn oil will get sucked out of the engine and into the cavities of the cylinder head, again getting burned.

If the car is misfiring (spluttering, running rough, stalling out, etc.,) you have a problem with the spark plugs or a cylinder. It could be bad spark plugs due to carbon build up or contamination, or they have gotten too wet. The spark plugs are just two electrodes with an arc (a gap between them and the electricity creates a spark in trying to pass). They wear down after a while which is why you have to change them regularly during tune-ups. If it isn't the spark plugs then it is an engine problem.

To summarize, engine problems can include:

a) cooling system problems

b) lubrication system problems

c) bad valves or incorrect valve clearances

d) bad pistons or piston rings

e) a broken seal or gasket

f) the timing coordination between the valves the pistons and the spark is off

g) insufficient spark

An engine in good condition will be well cooled, well lubricated, well sealed, well sparked, and well coordinated. Of course it has to be well fueled too!