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Oil Change Intervals

I own a 2001 Eclipse, of which I am the original owner. From day one I have used the same place to change my oil and have always had them use a quality synthetic blend meeting all requirements specified by the manufacturer. Despite the owner’s manual indicating oil changes at 7.5K miles, I’ve adhered to a 3K change policy. However, here I am at nearly 9 years to the day of ownership and am still just shy of 80K miles. At this level of driving it takes me at least 4, maybe even pushing 5 months to log 3K miles. I know they used to say to change at 3 months or 3K miles. As I understand it, blow-by and other contaminants can break down an oil with time, as well as through use, so am I damaging my vehicle by waiting for 3K miles, or should I be changing to a 3 month, regardless of miles, policy?

You’re actually changing it much more frequently than you need to.

In days long past, when engine’s were built with parts simply made to +/- drawing tolerances and carburators were intentionally pouring in more fuel than could be fully combusted in order to get suffucient power (the droplets were too big, they coalesced in the manifold, I’ll skip the full dissertation), unburned fuel used to get past the rings along with some combustion byproducts and dilute/pollute the oil. Oil needed changing regularly.

Today’s engines are so “tight” and todays fuel metered so perfectly (not a molecule is wasted) that oil stays much cleaner much longer. I use 5,000 miles or 6 months as a standard now. Many use even higher numbers, like 7,500 miles or one year.

Let me know if you decide to sell your Mitsu. Yours is one of the best maintained I’ve seen on this forum.

I would just change it every 3,000 or 6 months, whichever occurs first. You’re doing good, don’t worry about it.

Thanks guys, I appreciate the feedback! I used to be a mechanic, mostly front end work, but more than 20 years separates me from this profession. I’m glad to hear that tighter tolerances and fuel injection seems to have lessened the issues of old, and that engines can withstand these longer intervals, especially with modern lubricants.