Mouse Milk for AvGas Stains

[Nick G]

I saw on a previous post that someone had great success using mouse milk to remove a gas stains. Not sure if the details but has anyone used it with any success?  I’ve read all the threads on out other suggestions to remove stains, but it seems like limited success with everything else. 

[redbaron1982]

I guess it depends whether you're referring to 100LL or G100UL. Assuming that you use 100LL, then in my experience, stains are super easy to remove. I only got stains in a very small leak I have on one of my sump drain, it get heavily stained in blue. Usually I take it out with some WD40, not sure if it is the best, but it works for me. As it is on the lower part of the wing, it is not easy to see if there is a very faint staining left behind, for what I can tell, there is not.

[Nick G]

5 minutes ago, redbaron1982 said:

I guess it depends whether you're referring to 100LL or G100UL. Assuming that you use 100LL, then in my experience, stains are super easy to remove. I only got stains in a very small leak I have on one of my sump drain, it get heavily stained in blue. Usually I take it out with some WD40, not sure if it is the best, but it works for me. As it is on the lower part of the wing, it is not easy to see if there is a very faint staining left behind, for what I can tell, there is not.

Yes, 100LL. I e tried MEK and polishing compound. The stains have been there for a while. WD40 eh???

[redbaron1982]

Be careful with MEK, is very agressive. I heard people also use 100LL, yeah, kind of fight fire with fire. The logic behind using 100LL is that the stain comes from the fuel evaporating and leaving behind the dye. So with fuel you could remove the dye and as long as you remove the 100LL with a rag, it should be good.

[Nick G]

Just now, redbaron1982 said:

Be careful with MEK, is very agressive. I heard people also use 100LL, yeah, kind of fight fire with fire. The logic behind using 100LL is that the stain comes from the fuel evaporating and leaving behind the dye. So with fuel you could remove the dye and as long as you remove the 100LL with a rag, it should be good.

Yea I’ve seen that method too. I think it’s soaked deep into the paint. Does the WD40 remove all of the stain? You think it would work for soaked in stains?

[redbaron1982]

In my case, I've let the small leak from the sump drain build up a stain for several months, you could even feel a bump due to the heavy accumulation of blue pigments. WD40 removed all. I don't know what your specific case is and if this method would work.

[Nick G]

22 minutes ago, redbaron1982 said:

In my case, I've let the small leak from the sump drain build up a stain for several months, you could even feel a bump due to the heavy accumulation of blue pigments. WD40 removed all. I don't know what your specific case is and if this method would work.

It’s worth a shot. Mine is a surface stain that I keep wiping with a rag. 

[N201MKTurbo]

I use MEK. If you have good polyurethane paint, MEK usually won’t hurt it. I would try the MEK on somewhere inconspicuous.

If the stain is soaked into the paint, you are kinda screwed. MEK works best. It may take the paint off along with the stain.

[Nick G]

58 minutes ago, N201MKTurbo said:

I use MEK. If you have good polyurethane paint, MEK usually won’t hurt it. I would try the MEK on somewhere inconspicuous.

If the stain is soaked into the paint, you are kinda screwed. MEK works best. It may take the paint off along with the stain.

Thank you. 

[R Van Dyck]

I use spray Carb Cleaner on a rag and poof its gone. Like the other fellas are mentioning about the paint watch out. I have had deep blue under the wing and around the caps. A little dab will do ya...

 

Fly Smart

Ryan

[MikeOH]

I've always been successful with just using 100LL.

I'd sure recommend trying that before moving on to other chemicals.

[Nick G]

On 8/13/2025 at 7:07 PM, R Van Dyck said:

I use spray Carb Cleaner on a rag and poof its gone. Like the other fellas are mentioning about the paint watch out. I have had deep blue under the wing and around the caps. A little dab will do ya...

 

Fly Smart

Ryan

I may give that a try. Thx!!

[Nick G]

On 8/13/2025 at 9:05 PM, MikeOH said:

I've always been successful with just using 100LL.

I'd sure recommend trying that before moving on to other chemicals.

I tried just spraying WD40 on it and no luck. 100LL is next. I’m afraid it won’t get the deep stubborn long time stains but maybe I’m wrong. Hopefully I am!

[MikeOH]

3 minutes ago, Nick G said:

I tried just spraying WD40 on it and no luck. 100LL is next. I’m afraid it won’t get the deep stubborn long time stains but maybe I’m wrong. Hopefully I am!

Honestly, if it doesn't work I'd move on to rubbing compound, followed by polishing compound and wax before I used nasty chemicals that might really damage the paint.  If the stains are that 'deep' I think rubbing them out will be a lot easier to control the location and amount of paint removed.

[outermarker]

Smirking here...the question was if anyone has used mouse milk to remove the fuel stain.

"I saw on a previous post that someone had great success using mouse milk to remove a gas stains. Not sure if the details but has anyone used it with any success?  I’ve read all the threads on out other suggestions to remove stains, but it seems like limited success with everything else."

So, to answer the question, I have not used mouse milk to remove the fuel dye stain.  

However, I have also removed the stain by using fuel on a cloth. The dye transfers to the cloth easily, without much rubbing effort.

[Shadrach]

As mentioned before, MEK works but is aggressive. 

Acetone is gentler on the paint but is nearly as effective as MEK at dissolving avgas dye. The main challenge with acetone is that it evaporates rapidly, especially on a hot day when rubbing a hot airplane.  It's boiling point of 133°F is 50°F lower than MEK. It's also more than twice as volatile in terms of its vapor pressure rating.  Storing it in the hangar fridge helps to delay evaporation during use.  It is also way easier to obtain than MEK and relatively cheap.

[DCarlton]

On 8/15/2025 at 9:52 PM, MikeOH said:

Honestly, if it doesn't work I'd move on to rubbing compound, followed by polishing compound and wax before I used nasty chemicals that might really damage the paint.  If the stains are that 'deep' I think rubbing them out will be a lot easier to control the location and amount of paint removed.

After getting bladders installed, I wanted all the gunked up fuel stains removed.  I tried everything; 100LL, Acetone, Mineral Spirits, maybe MEK; can't remember.  I ended up hiring a detailer to polish and wax the plane.  They ended up doing exactly what you suggest; rubbing compound, polish, sealer, and a lot of grunt work.  I have no idea how many polishing pads they went through; I doubt they could be washed and reused.