Mineral oil it a common name for non-synthetic oil.

Really? Whenever I see mineral oil, I think of the stuff you buy in the drug store...

Learn something new every day :D

Is it necessary to replace these at every oil change? Why would this part wear?

I don't know. Some people replace em and some don't. I don't replace mine every time, maybe every other oil change. Every time you tighten down on the drain plug, it squashes the washer even more. Eventually it becomes totally flat and doesn't function anymore.

my oil is changed once a month

i drive over 120 miles a day. every day :( :( :(

I change it every 2500-300miles with Mobil 1 or some other synthetic blend.

I think this subject has been beat to death on every board I have looked at over the years. I can speak from experience as I regularly drive a car for over 150,000 without any oil consumption. The manufacture has spent a great deal of money and time testing their products in every situation you will ever come in contact with. They want their product to work well so they publish a maintenance policy with regards to what will be a responsible schedule to insure their products last for a long time (at least 100,000 miles).

That said; I put about 5,000 (give or take 500 miles) miles on my cars before I change the oil. I change the filter at the same time as the oil. I rotate the tries every other oil change. I have never had an engine fail in over 30 years. At one time I was driving mostly highway miles (1,000 per week) and in six years logged up almost 300,000 miles without any oil consumption. I now drive in town (0 – 45 MPH) in Florida. I have held to the same oil change schedule and have not had any engine failures. I use regular oil (not synthetic) and mostly go to the dealership for oil changes. They always give a discount to people that buy cars from them. In Orlando, my dealer changes the oil and filter for 14.99. Why would I want to change the oil for that? Look at the Mazda home page and follow the link to your dealership and you will most likely find a discount coupon for a oil change at least.

The dealer wants to make money and has a “dealer suggested maintenance schedule” that they would like everyone to follow. It allows for more money in their pockets over the life of the vehicle. It does not insure a longer life of the engine. This is not in your best interest, only theirs. Trust the manufacture, They have done a good job of testing their product and have hundreds of thousands of owner driven miles to back them up. Having major failures in their products is not a good advertising policy. They would go out of business in a short time if their products were failing in a short time for any reason.

Mobil1 @ 15,000 and new filter every 5,000. I had 4 cars that had >150,000 on them before selling them with out any problems using this schedule.