I’m about to work on a 1997 Honda Civic DX that has over 250,000 miles on it. A couple of days after doing a routine oil change, the oil light started flickering. I checked the level to make sure that it wasn’t low and it was fine. I did, however, switch from a
5W-30 to a 5W-20 that last oil change so that might be what’s causeing the problem (even though the recommended oil for that car is 5W-20).  I’m planning to use the MMO to knock out some sludge and grim from poor maintenance practices by the prior owner. I’m also going to replace the oil pressure switch to rule out a faulty switch bring on the light. Hopefully that will help the engine and fix the flickering oil light. After I do the cleaning cycle witht the MMO I’m going to use synthetic high mileage oil in conjunction with 20% MMO to help keep the engine sludge free. I am trying to find Mobil 1 5W-30 High Mileage Motor Oil to replace the conventional oil that’s in there now, but I can’t find the stuff anywhere. Seems like everyone sells the 10W-30 stuff but not the 5W-30 when it comes to high mileage synthetics. Have any idea where I can find a website or a store that will sell it or order it? Also any advise or changes you would make to this plan?

Also, I have heard that switching from conventional oil to synthetic oil in high mileage vehicals can cause oil leaks. It this true and if so will MMO help prevent oil leaking due to this?

I’ve never seen Mobil-1 high mileage around here either. Just the standard and extended service stuff. I would say that any store like Autozone or Advance could order it for you.

Any time you use a product that cleans deposits from the engine, you run the risk of opening up small passages in the gaskets that might only be plugged due to old grime and crud. I have never had this happen and I don’t believe that it is as common as some people would lead you to believe. Good luck and keep us informed.

Ok, thanks. I’m going to try switching the oils and see what happens. I’ll post the results here after it’s all said and done.

Just switched from Mobil 1 5-30 high mileage to Mobil 1 Advanced Fuel Economy 0-30.  Picked up almost 2 more MPG!  Got it (and the high mileage 5-30) at Wal Mart.  I’m in NW Arkansas.  I also add 4 oz. of MMO at every fill up.  I drive a `99 Old Bravada with 144,000 miles on it.  Haven’t had it long-had 139,000 when I bought it. 

I have heard of a few cases with older engines where synthetic oil cut so much sludge loose it could plug the oil filter.  I’ve never had a bad experience when swapping to synthetic myself.  However, you may need to change oil earlier the first couple of oil changes as it does clean out your engine.

I finally found some (Mobil 1 high mileage 5W-30) at an Auto Zone, but I had to drive a ways to get to it. I just did a oil system flush with GTX conventional high mileage oil with 25% MMO, drained the oil again and refilled with Mobil 1 high mileage with 20% MMO and a new high performance Mobil 1 oil filter. Hopefully this will not only clean the engine, but help it get some lost power and smooth operation back from its old age.

kirby - 05 March 2010 05:28 PM

I have heard of a few cases with older engines where synthetic oil cut so much sludge loose it could plug the oil filter.  I’ve never had a bad experience when swapping to synthetic myself.  However, you may need to change oil earlier the first couple of oil changes as it does clean out your engine.

A similar thing happened to me with my youngest daughter’s car.

My youngest daughter had a 1990 Ford Probe that I switched to Amsoil when she purchased it with 87,000 miles on it. The Amsoil dislodged sludge in the engine to the point of causing restrictions in some of the oil passages. My mechanic suggested MMO to try to flush out the restrictions in hopes that a disassembly would not be needed. It worked and I’ve been an MMO fan ever since.

Well it has been almost 2 weeks since I did the oil change with MMO and everything seems to be working fine. No leaks as far as I can tell and hopefully it is in the process of cleaning out that engine. I’ll just have to continue to wait to discover just how well it works with such a high mileage vehical.

Hmmm, according to the Amsoil lookup guide, no Civic engine of that year calls for 5w20. Could be wrong, but maybe that’s why the oil light came on?

If your engine was pretty sludged up, I’d change the filter half-way thru the OCI. If the filter gets plugged up and goes into bypass mode, you’ll not be removing additional sludge. Filters are pretty cheap and I’d rather know I was doing the best I could to clean the engine up.

CAC7 - 04 March 2010 07:14 AM

Also, I have heard that switching from conventional oil to synthetic oil in high mileage vehicals can cause oil leaks. It this true and if so will MMO help prevent oil leaking due to this?

This is a complete myth. Switching from conventional oil to synthetic oil will not cause leaks, even in a high mileage engine.

-Techniker

That is true, my car has 191k on it and i switched to synthetic 6k miles ago. Before that I ran Dino oil with MMO twice and then switched to synthetic, runs great.

Same case with a 01 buick regal with 91k, first time switching to synthetic and runs great as well. Prior to that I ran dino with MMO for 2k.