Did I ruin my engine?

I think I started my engine on the way to ruination and I do feel
stupid.

Vehicle is a simple Voyager, 1994, with 203,000 miles.
It was not smoking although it has the infamous 3.0 liter Mitsubishi
engine.
Very tight engine considering the miles and its heritage.

I was changing the oil every 3000 miles.

I let the oil go for 4,500 miles and 9 months instead of the usual 3
months.

But what is worse, I added 2 quarts in 9 months of plain SAE 30 weight
oil.

It had 5W-30 Conoco-Phillips semi-synthetic blend which was doing well.
Before I would add 10W-30 regular oil to the blend. My poor logic was
that SAE 30 is a single weight and less interfering with the 5W-30 and
since the temps were above 32 F, should not matter.

Now idling, I hear something. It idles rough. It is smoking at idling.
Don't think this is normal. But under way, it does not smoke and is
quite smooth. The engine sounds fine if moving along and not idling.
That is encouraging. Don't hear any strange noises when moving.

Also, did not replace the oxygen sensor for many months. Did quite a
bit of non-highway driving. Was told this cannot harm the engine but
only the catalytic converter. Not sure about all of that. The mileage
is quite good even with these problems.

I hear the valves tapping upon starting. Usually goes away in 2 minutes
now. Used to go away in about 15 seconds.

I am not sure if the noise I hear is the alternator going, motor
mounts, or other things fixable. I'm concerned about valve damage,
engine knocking, and even piston slap. If I did do damage to the
engine, which seems unlikely, but something occurred and it may or may
not be a coincidence.

What do you all think? Tell me even if it's not pleasant. I think I
pushed the poor engine to accelerate its aging. It's too old to take
even the slightest abuse.

 

The Mitsubishi 3.0L is notorious for upper engine/head valve noise. Using
synthetic oil and warmer weather seems to help it quiet down sooner. Live
with it or rebuild the heads.

make sure you change the timing belt every 60K miles and keep the oil full.

The noise could well be an alternator bearing or water pump or such, but is
probably just the valves not getting oil which as I said seems normal for
this engine.

Bob

 

I don't think you've influenced its life all that much. Mixing weights is
not ideal, but it's not really bad enough to cause rapid wear. The thing has
200k on it already, so you can expect some wear and tear issues no matter
what you do.

 

What synthetic oil would you recommend? I gather a 100% synthetic is
now okay to put into very high mileage engines? Previously this was a
no-no because of possible leakage of engine seals with the pure
synthetic. But this turned out to not be the case, I gather.

If the timing belt breaks prematurely, this should not ruin the engine
because it is a non-interference engine? Or can it do any damage?

 

I use Mobil One 10W-30 full synthetic on my 135K Mitsubishi 3000SL with the
3.0L engine. It badly needs the heads re-done, but continues to plug along
.... it takes about 3 or more minutes to quiet down and sounds a lot like our
washing machine till then!

Bob

 

There's diagreement on that from a
dissolving-old-sludge-residues-and-clogging-the-galleys-or-lifter-ports
standpoint. I'm a firm believer in that being the case, though there
are many that will (and do) violently disagree with me. As my
grandmother used to say, you pays your money and you takes your chances.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')