Water/Methanol - Does it go bad?

[Red Snake]

I have a Roe w/m kit installed. I have a large plastic tank installed and I don't drive my car very much. If the w/m tank sits all winter will the methanol evaporate and leave my mixture "weaker" or will the mixture be just as good next spring as it was this summer?

 

[mjorgensen Woodhouse]

It can, I would just drain and refill if you are concerned, cheap insurance.

 

[plumcrazy]

tom will answer i hope but i think it definitely does if its been opened before.

 

[Tom F&L GoR]

Yes, it is true that the methanol (which has a lower boiling point and a lower latent heat of vaporization) will be "lost" more quickly. In fact, it was of such interest to some grad students, they studied the evaporation rate of various water-ethanol mixtures. A 50-50 mix became a 71-29 mix after sitting out for a week. Keep a lid on the container and you can judge the effect by watching the container level.


Bayblab: Evaporation Rates of Ethanol Solutions
Fluids - Latent Heat of Evaporation

 

[Tom F&L GoR]

Yes, it is true that the methanol (which has a lower boiling point and a lower latent heat of vaporization) will be "lost" more quickly. In fact, it was of such interest to some grad students, they studied the evaporation rate of various water-ethanol mixtures. A 50-50 mix became a 71-29 mix after sitting out for a week. Keep a lid on the container and you can judge the effect by watching the container level.


Bayblab: Evaporation Rates of Ethanol Solutions
Fluids - Latent Heat of Evaporation

This seems like a good candidate for the "Questions" series.

 

[Red Snake]

Thanks for the info Tom. Looks like I'll drain and refill before I get the car out for the spring.


If there were data regarding the evaporation rate in a covered container I might be able to recalculate a "recharge" rate and just add some methanol to the mix. This test involved an open container so it's not quite the same circumstance.

 

[99 R/T 10]

Yes, it is true that the methanol (which has a lower boiling point and a lower latent heat of vaporization) will be "lost" more quickly. In fact, it was of such interest to some grad students, they studied the evaporation rate of various water-ethanol mixtures. A 50-50 mix became a 71-29 mix after sitting out for a week. Keep a lid on the container and you can judge the effect by watching the container level.


Bayblab: Evaporation Rates of Ethanol Solutions
Fluids - Latent Heat of Evaporation

The tank does have a lid on it. That being said, it should keep the mix close to 50/50(or what ever you want), correct? If you want to add insurance, just add a bottle of HEET(yellow bottle). 99.99 ****.

 

[Madduc]

But there is a small vent in the cap. So I wonder how much that would let the mix to evaporate? I drain the mix out when i put my car away for winter. Then I disconnect the lines from the nozzles and run some RV antifreeze thru it. Then in the spring put in a fresh batch.

 

[Tom F&L GoR]

Don't forget the student's test was with ethanol, not methanol. Methanol would evaporate more quickly. My $0.02 would be to note the fluid level in the closed, vented container, put a paperclip or pencil in the vent, and note the fluid level. Then assume whatever evaporated was the methanol and add back later. (99 RT/10 method.)

Methanol doesn't freeze until about -140F so I don't think flushing with RV antifreeze would be needed.

 

[Red Snake]

Don't forget the student's test was with ethanol, not methanol. Methanol would evaporate more quickly. My $0.02 would be to note the fluid level in the closed, vented container, put a paperclip or pencil in the vent, and note the fluid level. Then assume whatever evaporated was the methanol and add back later. (99 RT/10 method.)

Methanol doesn't freeze until about -140F so I don't think flushing with RV antifreeze would be needed.

Good idea.

 

[ViperBing]

Is there a way to check the amount of methanol to water mix, say by checking the Specific Gravity?

 

[Tom F&L GoR]

Yes, that should work. SG of MeOH is 0.79, water of course is 1.0.

 

[Madduc]

I use the RV antifreeze to flush out the pump mainly. Isn't the methonal ******* the pumps seals over time? Or could enough of it evaporate over the winter and leave a weak enough mix of water to then freeze in the pump or lines?