[MSCW list] Oil for N/A's

Timothy Metzinger tim.metzinger at outlook.com
Mon Oct 9 02:02:41 CEST 2023

Others have commented, but I'll add my two cents.  Synthetic oils are ABSOLUTELY "compatible" with older engines.  They meet or exceed all the standards for lubrication.  In fact, they're so good that they can "slip by" oil rings and some seals and gaskets, and your car may burn oil as a result.  If the leaky seal is a front or rear main seal, you may spot some oil outside the car.  The synthetic blends made for high mileage cars add things that will cause seals and gaskets to swell, but can't do anything for worn rings except stop them from wearing any more.  

My NA 1.6L was on M1 0W40 from the time I got it, (with 18 years and 130K on it), and eventually the engine needed to be rebuilt as it was using (though not LEAKING) oil.  But on the rebuilt engine, I used M1 5W30 from break in until the crash (about six years), and it NEVER needed oil between fill-ups and the oil analysis had me changing the oil at 10000 miles or on year.

My 2015 NC had 30000 miles when I bought it in 2020, and it's been on M1 0W20.  I started out with changes at 5000 miles, but over the past three years and 40000 miles I've never needed to add any oil, and based on the oil analysis I now change the oil and filter every 11,000 miles or annually.

As previously noted, a good synthetic will likely keep the engine from wearing.  Significant engine wear issues requiring rebuilds are gonna be very rare.  I can expect seals and gaskets to need replacement, just because age and thermal changes are what kill those components, NOT wear.  Really, you need to start thinking about oil as two factors - what does it do for metal-on-metal wear, and what does it do to/for the seals and gaskets?

So I agree with Richard - if your current engine isn't dripping or burning oil, put a high-mileage synthetic in it, and increase your change intervals - the old "3000 miles" interval doesn't make sense for modern synthetics. If you're not racing it, 5000 miles is probably fine, although I do recommend oil analysis guiding you as you find your new change interval.

-----Original Message-----
From: MSCW <mscw-bounces at lists.mscw1.com> On Behalf Of Benita Jenkins via MSCW
Sent: Saturday, October 7, 2023 8:42 AM
To: mscw at lists.mscw1.com
Cc: Benita Jenkins <jenkinsbenita at yahoo.com>
Subject: [MSCW list] Oil for N/A's

Mazda Sports Cars of Washington (MSCW), Social Group List Serve

I just read that synthetic oil  may not be compatible with some older engines! Synthetic motor oil may cause leaks or damage to the seals and gaskets of some older engines that were not designed for it. This is because synthetic oil has different properties and additives than conventional oil, which may not suit the specifications of some engines.  I am curious if any MSCW members have any experience/opinions on this?

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