Decelin and Techron

[outermarker]

I read that both Decelin (better than TCP) and Techron are approved for Continental and Lycoming engines. Does this also mean these two products won't harm the sealant used for Mooney fuel tanks? Will MMO harm the fuel tank sealant?

thanks!

[EricJ]

16 minutes ago, outermarker said:

I read that both Decelin (better than TCP) and Techron are approved for Continental and Lycoming engines. Does this also mean these two products won't harm the sealant used for Mooney fuel tanks? Will MMO harm the fuel tank sealant?

thanks!

No, it doesn't mean that.    Airframe approval is separate from engine approval.    This is why the limitations in the aircraft POH and specs in the aircraft TCDS drive rather than what's in the engine TCDS.

[outermarker]

I assumed as much. I was hoping from all the past and present owners that someone, or many, have used these products and could provide testimony that the products won't harm the fuel tank sealant.

[EricJ]

10 minutes ago, outermarker said:

I assumed as much. I was hoping from all the past and present owners that someone, or many, have used these products and could provide testimony that the products won't harm the fuel tank sealant.

I wouldn't recommend putting MMO in the fuel tank, although some do that.  It may increase the likelihood of a tank leak.   It's more often an oil additive, especially just before an oil change.

[varlajo]

I know several pilots who add some MMO to their oil for the last flight prior to oil change. I wouldn't dump MMO or any additives into fuel tanks though. 

[N201MKTurbo]

When I bought my old Cessna I acquired a gallon of pure TCP. It was added to the fuel to keep the plugs from fouling. The O-300 in that plane was designed for 80 octane fuel. 100LL fouls the plugs and the TCP was supposed to help. 
 

I worked on fueling systems for jet drones. The engines did not have an oil system and they were lubricated with fuel. TCP as added to the JP-10 to lube the engine.

https://www.prattwhitney.com/en/newsroom/news/2017/08/03/small-but-powerful-the-tj-150

 

[Pinecone]

Back in the days when 80/87 was going away.  A number of people believed that a bit of MMO in the fuel reduced the incidence of sticking valves from the excess lead.

TCP worked quite well but you had be careful handling it as it was very toxic.

And FYI, MMO contains a bit of TCP.

[OR75]

5 hours ago, outermarker said:

I read that both Decelin (better than TCP) and Techron are approved for Continental and Lycoming engines. Does this also mean these two products won't harm the sealant used for Mooney fuel tanks? Will MMO harm the fuel tank sealant?

thanks!

curious where you read that 

[1980Mooney]

7 hours ago, outermarker said:

I read that both Decelin (better than TCP) and Techron are approved for Continental and Lycoming engines. Does this also mean these two products won't harm the sealant used for Mooney fuel tanks? Will MMO harm the fuel tank sealant?

thanks!

 

2 hours ago, OR75 said:

curious where you read that 

Because Decalin is not approved for any Certified Aircraft Engine.

From the Decalin Chemicals web page  https://decalinchemicals.com/products/decalin-runup-fuel-additive/

"Decalin RunUp is not approved for use in the engines of certified aircraft but it has the same active ingredient, Tri Cresyl Phosphate as our previous product."

Perhaps the comment came from an Experimental Aircraft owner.  Decalin states "Lycoming clone users have reported very good results when using this product."  It is not approved by Rotax either but some people use it.

Same thing with Techron.  Some Experimentals may experiment with it but it is not approved for any aircraft application.  

The only approved Fuel Lead Scavenger Additive is Alcor TCP - and that is only approved for Non-Turbocharged engines from Lycoming, Continental and Franklin.

TCP Fuel Treatment | Alcor, Incorporated

On some of the Experimental Owners sites, owners comment that they prefer Decalin over Alcor TCP for price but also because they complain of the harsh chemicals in Alcor TCP.  That sounds like a "red flag" for use in our tender Mooney wet wing fuel tanks......

 

[PT20J]

MMO isn't going to dissolve your fuel tank sealant. It is mineral spirits, a little oil of wintergreen, a bit of TCP and a couple of dichlorobenzene isomers to dissolve carbon and lead deposits. https://marvelmysteryoil.com/pages/sds

 

[1980Mooney]

38 minutes ago, PT20J said:

MMO isn't going to dissolve your fuel tank sealant. It is mineral spirits, a little oil of wintergreen, a bit of TCP and a couple of dichlorobenzene isomers to dissolve carbon and lead deposits. https://marvelmysteryoil.com/pages/sds

 

That may be true.  However, many years ago I used MMO routinely as a fuel additive to reduce lead deposits.  I started to notice spots on my old graying wing walk getting darker - like where a screw was under the black wing walk.  And the wet spot did not go away even after I discontinued using MMO.  My theory is that the screw might have been leaking just a very tiny bit - so little that it would normally evaporate away the AVGAS without darkening the wing walk.  But I believe that the MMO left behind and deposited some of that oil of wintergreen as it evaporated resulting in a darkening circle/spot on the grayed weathered wing walk.  I stopped using MMO after that.

[PT20J]

1 hour ago, 1980Mooney said:

That may be true.  However, many years ago I used MMO routinely as a fuel additive to reduce lead deposits.  I started to notice spots on my old graying wing walk getting darker - like where a screw was under the black wing walk.  And the wet spot did not go away even after I discontinued using MMO.  My theory is that the screw might have been leaking just a very tiny bit - so little that it would normally evaporate away the AVGAS without darkening the wing walk.  But I believe that the MMO left behind and deposited some of that oil of wintergreen as it evaporated resulting in a darkening circle/spot on the grayed weathered wing walk.  I stopped using MMO after that.

Maybe. But the amount of methyl salicylate in MMO is small and you are only supposed  add 4 oz per 10 gal of gas. 

[1980Mooney]

14 minutes ago, PT20J said:

Maybe. But the amount of methyl salicylate in MMO is small and you are only supposed  add 4 oz per 10 gal of gas. 

I typically added it before long trips. The night before the trip I would fuel at the self serve to a total of 80 gallons on board - 40 gal per side and then pull it back to my hangar.  Once I got it back in the hangar I immediately added 16 oz MMO to each side - most in the main and some in the Monroy outer tank.  The MMO would seem to run to the bottom of the tank.  Even after vigorously shaking the wings up and down it would not mix well in the main tank.  Samples from the tank drain would be mostly MMO which I poured back in the tank.  By the next morning it was better dispersed, but the tank was exposed to uneven concentrations during that time.

Adding the MMO while simultaneously fueling was not ideal.  Sometimes I was fueling in the dark.  During the day, other planes might be waiting for the lone self serve pump and I didn't want to be diddling around measuring and adding.  It was easier to do it back in the lighted hangar....but still not ideal.

[Pinecone]

Premeasure two 16 ounce bottles of MMO.  Add one to one side, fill tank.  Go to other side, repeat.  No waiting.

[1980Mooney]

2 hours ago, Pinecone said:

Premeasure two 16 ounce bottles of MMO.  Add one to one side, fill tank.  Go to other side, repeat.  No waiting.

Other than the cost, inconvenience, bottles didn't seem to seal tight after opening if stored in plane, and the smell it leaves on you after you touch anything with it, I could not detect that Marvel Mystery Oil did anything other than make the satin gray exhaust deposit on a properly leaned tail pipe a slightly browner shade of gray.   If it actually did something beneficial that could be documented, everyone would be using it and it would be preblended in all fuel.   Perhaps that is the "Mystery "in it.....

[EricJ]

4 hours ago, 1980Mooney said:

Other than the cost, inconvenience, bottles didn't seem to seal tight after opening if stored in plane, and the smell it leaves on you after you touch anything with it, I could not detect that Marvel Mystery Oil did anything other than make the satin gray exhaust deposit on a properly leaned tail pipe a slightly browner shade of gray.   If it actually did something beneficial that could be documented, everyone would be using it and it would be preblended in all fuel.   Perhaps that is the "Mystery "in it.....

It works well as an oil additive in some cases, and some have found benefit as a fuel additive.    It's been used in aviation since before WWII and was shipped in 50 gal drums for use in the big radials in WWII.   MMO has a long history of beneficial use in aviation, but it's certainly not a cure-all and needs to be used carefully IMHO.

It does seem to be heavier than fuel, and if you add even a little bit at the top of a tank of 100LL and then take a sample from the sump, it'll be clear or discolored and smell funny almost immediately.   Some people think it makes the fuel at the sump smell like paint thinner.

Since many tanks have been patched over the decades with unknown methodologies, it is not unheard of that a non-leaking tank may start to leak a bit after the addition of MMO.    In the case I was involved with a previously non-leaking tank started leaking (weaping a little in two spots) and stopped leaking after the MMO was run out of the tank, so perhaps the sealant hardened back up a bit.  I know of another case with a PA-28 tank that leaked after the owner started using MMO.   The history of that tank is unknown as well, but it can happen.   On the other hand, many people use MMO in their fuel regularly and don't experience leaks.   I suspect tanks that have been patched with non-standard or non-approved sealants may be the most susceptible, but that's a guess on my part.   The tank that sprung two leaks and then fixed itself looked like a calico cat inside, so it appears to have been patched over the years with a number of different sealants.    In any case, I suggest using MMO in fuel tanks cautiously, at least initially to see whether it causes any problems.

[A64Pilot]

21 hours ago, Pinecone said:

Back in the days when 80/87 was going away.  A number of people believed that a bit of MMO in the fuel reduced the incidence of sticking valves from the excess lead.

TCP worked quite well but you had be careful handling it as it was very toxic.

And FYI, MMO contains a bit of TCP.

I have seen more than one R-1340 that will stick exh valves unless MMO is added to the fuel.

Having said that I don’t run any additives in my airplane.

Unless things have changed MMO is not approved, but it’s been widely used for decades, probably before I was born. Who formulated it and what it was formulated for is an interesting story.

https://marvelmysteryoil.com/pages/our-story

I have heard but do not know that’s it has changed ownership and they changed the formulation, I don’t know if any of that is true. It does keep my air tools clean and I think lubricated.

Edited May 13 by A64Pilot

[Pinecone]

8 hours ago, 1980Mooney said:

Other than the cost, inconvenience, bottles didn't seem to seal tight after opening if stored in plane, and the smell it leaves on you after you touch anything with it, I could not detect that Marvel Mystery Oil did anything other than make the satin gray exhaust deposit on a properly leaned tail pipe a slightly browner shade of gray.   If it actually did something beneficial that could be documented, everyone would be using it and it would be preblended in all fuel.   Perhaps that is the "Mystery "in it.....

Find some of the old MMO quart cans.

The place I saw it helping was in engines there were designed for lower than 80/87 octane running on 100LL.

[PT20J]

A couple of mechanics I know swear by MMO for flushing stuck rings. Use the Savvy procedure using MMO as the solvent.