1998 Corolla with 95K miles

I have an excellent car that runs like a charm. But it is getting old and I want to keep it running for another decade. (if possible!). So do I need to change my spark plugs now?? I do not see any drop in mileage and the car runs pretty smooth. I have never changed my spark plugs ever.

What does your owner’s manual say about changing the plugs? Regardless, if they’ve been screwed in that long you run the risk of them getting stuck in there. Carefully remove them. When replacing, spread anti-sieze compound on the threads.

Have you done any upkeep,changed fluids besides oil,water,trans,brake and power steering fluid?
Have you ever done water pump,timing belt? It is time,past time for all of this.
Find someone you trust or good local shop,ask around. Do not use tire,trans or quick lube places and do not do a flush on auto trans.
Yes this stuff costs but if you keep stuff done by the book there is no reason it will not make 250,000-300,000mi

To me, a 12 year old car with its original spark plugs sounds suspiciously like a car that has not had various types of necessary maintenance.

The first step is to open the glove compartment, take out the Owner’s Manual, and see what maintenance procedures are listed for 30k miles, 60k miles, 90k miles, etc. Note that each of those mileage driven intervals also has an elapsed time value, such as “90k miles or 90 months, whichever comes first”. Somewhere in that list, there is sure to be a listing for spark plug replacement, along with other vital items such as replacement of the air filter, fuel filter, coolant, etc. If these items have not been done according to the elapsed time intervals listed in the maintenance schedule, then truthfully I don’t see this car making it for another 2 years without major, very expensive repairs.

Perhaps I am wrong about other maintenance items having been skipped, and if I am wrong, I apologize for the assumption. However, even if the only maintenance item that has been overlooked is the spark plugs, that does not bode well either. As Goldwing noted, spark plugs that have been in place for 12 years are likely to have seized in their threads, thus leading to damage to the cylinder head when they are removed. Luckily, that type of damage can be repaired, but damage to the cooling system from not changing the coolant will be expensive to repair, and other parts of the car are negatively affected by keeping air filters and fuel filters in place for too long.

Even if the maintenance schedule does not list changing the transmission fluid, that should be done at the next service. When trans fluid is not changed every 3 yrs/30k miles, trans failure can take place any time after ~90k miles, and is pretty much of a sure thing after ~125k miles. When the transmission on an older car fails, the cost of overhaul almost always exceeds the book value of the car, meaning that the car is then “totaled”.

For the sake of your wallet, I urge you to open that manual and compare your maintenance receipts (you do keep them, I hope!) to the listed maintenance procedures. This makes a major difference in both the longevity of a car and the amount of money that it costs to keep that car running.

I have done a decent amount of maintenance on this car. Lets see… I do a transmission flush every 15K miles or so a coolant flush every 30K miles, changed my serpentine belts, resurfaced my rotors and changed out my brake pads, replaced the brake fluids in the process. I haven’t changed the steering fluids yet. I do have a good mechanic to take my car to and he sends me a quote every time about the spark plug change. To me it seemed like the risk of not changing the sparks was not so much… Now that you mention seizure of the threads, I will probably take it in.