Hey All,

I've been reading ALOT of information on running Mystery Oil in the fuel systems.
What many people are concerned about is; the Mystery Oil eventually causing failure to catalytic converters.
Has anyone have "Cats" fail, due to gasoline additives?

I've been running Mystery Oil in my fuel for about 6 months now; on my '07 4.6L F150. Just wondering if it's starting to cause some issues with the "Cats".
I haven't noticed a power loss of any sort.

What do y'all think?
I'm not trying to "ruffle" any feathers; just been reading too much on the subject, I guess.

Thanks!

 

I guess my question is WHY are you running oil in the fuel system ? What good is it doing ?

 

Hey Steve,

I've always ran Mystery Oil in my trucks, especially as they started getting "older". One of the reasons, to keep the fuel pump assy. conditioned and lubed-up. (I know what your thinking; the fuel pump assy. is designed to be submerged in gasoline.) When Ford and many others started designing vehicles with parts and assemblies that were lighter in weight; neglecting the focus on longevity; case-in-point, PLASTIC Intake manifolds. I'm on my second intake manifold, at only 100,000 miles.
I figured, let me do what I can to extend the life of the truck. That being said, I need to find-out if running Mystery Oil is actually harming the Cat.'s on this '07 F150. My last '95 F150 had the original Cat. on it; and the original fuel pump and injectors, when I sold it with 250,000+ miles on it. I ran Mystery Oil in it all the time, once it hit around 75,000.
The other reason; is Mystery Oil is supposedly good for the injectors also.
I miss that old '95 F150. It had the ole 4.9L straight six in it; way more "working" torque than the 4.6L. The old 1/2 ton trucks were as tough as the 3/4 ton trucks are today; but they were also worse on fuel economy.

Have a great 4th of July!

 

Oil or excess fuel inside the CATS is not going to be a good thing.. Nobody can tell you HOW MUCH before you screw up the CAT.. I sold my 2001 with the original fuel pump and manifold at 250 K miles. ( Manifold has nothing to do with the oil usage)... I have a 2002 now and original manifold at 175 K miles... I put a new fuel pump on a month ago for " general maintenance"... I also changed out the starter motor and alternator at 150K miles... not due to failure, but "general maintenance".

 

Hey Steve,

When I mentioned that I was on my second PLASTIC intake manifold; I wasn't implying it had something to do with the Cats.
I was just bringing up one of many things on the trucks today; that are bad engineering decisions.
Another bad idea: the 4.6L has it's spark plug journals straight up and down; so lots of "goodies"
Collect in there.
I miss the old trucks hahaha!

Have a great one!

 

I've used MMO before but now only use Startron stabilizer/cleaner. I use this in every gasoline engine on the place. I pretty much stopped using MMO after noticing it gums up over time. I saw this in my air tools and I also had trouble with a 2-cycle trimmer - I was adding some to my 2-cycle mix and over time I started to have a lot of trouble with it. All I did was stop using MMO in my mix and the trimmer is about 75% cured. As much as I liked MMO in the past I guess I have to now say you can find better things to use. In my experience of 20 years using Sta-Bil and Startron, if you want to preserve your fuel system and have less carbon build-up, its the thing to do. I've never had to have fuel system service on any vehicle in this time and the cat. converters stay sweet.

 

Saxman,

Thanks for the reply, I'll look into Startron.
I wonder if Marvel changed or "modified" their formula of Mystery Oil, over the years. That's not good if it's "gumming" things up.

Have a great one!

 

I have also heard that Sea Foam will plug up your converters, have you heard anything about that?

 

No, never that one before. I really don't think MMO will either unless you really overdose the fuel with it.

 

A cat heats up from unburned hydrocarbons to much unburned hydrocarbons can heat up the cat to much but you always want the cat hot enough so it helps clean up that tail pipe. will oil in the fuel system cause your cat to fail honestly that's just a personal opinion and I would believe that most of that oil would be burned from the combustion procces anyways and that little extra amount that makes it threw probably does not even make a difference in the life of the cat

 

a leaking fuel injector can damage a CAT...... don't take much "extra".

 

There was a guy on the van forum who ran a transport service and had 4 vans over 1.3 million miles each(!)

3 were 5.4's and 1 was a 4.6 if I recall correctly. He did not use snake oil additives. The vans got oil changes every 10k miles if the drivers remembered to take them in. Gasoline additives are a waste of money in modern engines IMO. In my early years of driving, I bought into additive advertising and put all kinds of stuff (including MMO) into my gasoline and oil to try to make my engines run cleaner or better, or burn less oil, whatever. In retrospect, there was no magic.

Modern gasolines have additives that provide all the detergents you need; use Top Tier fuels to make sure you are getting a good slug of additives in regular gasoline and you should be fine.

Unless your engine has over a million miles on it, it is not "older" based on how far the mod motors can go with reasonable care and maintenance.

George

 

very well said George........ 100%

 

LOL! Go for it! You do your thing and I'll do mine. I can use my own experience as proof, but you have no proof that I'm wrong - only mule-headed smugness. All fuels do not have adequate or Tier 1 levels of additives. Many of us also are forced to use E10 which is known to deteriorate rapidly and cause various problems in fuel systems. In my case, I believe all three of my vehicles are 'special' and require extra additive (cleaner/stabilizer such as Startron or Sta-Bil). One is my truck, which has fuel injection and is subject to sitting for weeks at a time. This is a bad situation for any fuel much less E10. I don't want to have a stuck injector. 11+ years now and 26,000 miles and it still runs perfect.
Two, my KIA Sportage turbo; there have been problems with the 2.0L T engine. It puts out 120 HP/Liter which is pretty stout, and KIA insists that it is to use regular gas. I use Tier 1 mid-grade fuel w/Startron and special synthetic oil. After two years I only have 18000 miles but it continues to run great. I stand on it fairly often as I have always done with cars but with this one its particularly enjoyable. With AWD and a 'sport mode' button, nailing it from a stop produces only acceleration, no wheelspin.
Three; the Honda Odyssey with Variable Cylinder Management. This engine type has had problems resulting in major work or replacement. Apparently the 'off' cylinders experience oil fouling which fouls the plugs and eventually damages the cylinders. In this I use special synthetic oil and the Startron. Anytime I get the chance to drive it I tend to let my fat right foot bear down on it at every opportunity - the point being to use those 'off' cylinders and hopefully keep all cylinders clean as the system enriches the mixture containing the extra detergents/solvents. These will throw clues when they start to go bad, including oil consumption, premature oil darkening and rougher running. So far under my ministrations and nearing 50,000 miles, we enjoy smooth, powerful performance with no symptoms. This hulk can get 30-31 on the interstate at 75 MPH with the AC blowing. After owning this, I probably would not buy another Honda. Its a pretty good vehicle but it has aggravating problems like rotors that produce pulsation and have to be refaced/replaced, and of course the specter of engine failure along with some other things.
So, I hold that depending on your vehicle, special treatment, such as premium synthetic oil and certain fuels/additives may be what you need to ensure long life and smooth performance.
Finally, I always have to laugh at the anti-oil/fuel-additive guys because of one fact - additives over the years, going back to the 1920s, eventually became standard in the 'off-the-shelf' oils and in pump gas. So what is happening is the 'snake oil' of today eventually becomes 'the latest thing' in the major brand products. Of course, I do not imply that everything out there will eventually turn out to be useful - some things really are 'snake oil', but you have to have a 'feel' for what you need and exactly how you expect it is going to help you.

 

I do put Sta-Bil in my lawnmower/snowblower gas can (and wish I could buy gas without alcohol in it), and will admit that I dose my garage queen 1991 BMW some Sta-Bil for winter storage (I drive it under 1000 miles per year). I have not owned any engines with VCM and have avoided direct injection so far, but don't believe that much more than Top Tier fuel could help engines with special problems. For instance, the early German DI engines did carbon up intake valves but no fuel additive could help that because there was no fuel that made it past the back sides of the intake valves. You could force-feed Seafoam thru the brake booster hose and clog the catalytic converters....better to remove the intake manifolds and walnut-blast the intake ports and valves.

If an engine has a design deficiency, there are times when additives are officially recommended. For instance, Subaru EJ engines were known to eat head gaskets, and Subaru sold and recommended a specific "cooling system conditioner" that was basically stop-leak to head off seepage. There is no manufacturer that recommends Marvel Mystery Oil but many manufacturers recommend Top Tier fuels and I buy Top Tier over 95% of the time (making an exception when I have to stop at a turnpike plaza on vacation or something).

I have also had some excellent results eliminating torque converter shudder issues on my old Ford van using Shudder Fixx (which is basically a friction modifier like limited slip additive), and recommended the stuff to a friend with an Odyssey--and it worked for him as well. So I am not totally anti-additive but adding something like MMO to fuel for a 4-stroke engine with catalytic converters is not useful for any reason I could imagine.

Thinking that a 100k mile engine is "high mileage" and has special needs for MMO is not realistic IMO--this is no longer the 1960's and I can see far more danger than benefit in using this stuff. Mod motors routinely go 500k miles without additives and a few of them go over a million miles, again without additives. So in this particular discussion, I will call MMO "snake oil" but will endorse Sta-Bil for storage, Top Tier fuel for a regular diet, and, if needed, Shudder Fixx for torque converter shuddering.

Full Syn oil is something I would use if the mfr required it or if I was running a turbo engine with high output. For a basic engine like a Ford 4.6 V8, Motorcraft syn blend is fine. (I ran full syn in my van for about 20k miles when I got a case for 99 cents a quart, saw no improvement in performance, consumption, or gas mileage.) If you want to lengthen oil change intervals a bit, full syn is fine also. But the guy with the 1.3 million mile vans did not use synthetic oil and wasn't even sure what brand his service guy was using.

George