It’s career day at Alt-F4. Well, not really especially since I have never had the title of chemical engineer. However, I have done the job. A chemical engineer does a lot of scaling, unit conversions and process type work. I spent over four years doing very similar work early in my career.

So, why the heck do you really care what a chemical engineer does? Well, from a practicality standpoint sometimes you have to do some unusual stuff. In my case, I am still struggling with the leaf blower, I bought some 40:1 fuel thinking that was probably the ticket. I incidentally ran across the manual this week and discovered that it is supposed to actually take 16:1 fuel mix.

First, good luck finding a 16:1 pre-mix in the store. I don’t think any of the modern engines run that kind of ratio. If you are going to make it yourself, that is 8oz of 30 weight oil to 1 gallon of fuel. I don’t really want to make a gallon especially now that I have almost a full gallon of 40:1 that is not really useable in any of my other machines. Another added bonus is that I could make 40:1 into 50:1 in the same way to use in my trimmer or chainsaw. This avoids having a bunch of cans of different mixes lying around because I don’t use that much anyway.

Another thing that I don’t want to do is leave a bunch of fuel in the the tank. I don’t know when or if I will use it all. So, my plan is to make up 1 cup at a time of 16:1 out of the 40:1 that I already have. I have to do some relatively simple calculations so I can use the equipment that I have to do what I want.

  1. Work in units that are ten based (i.e. metric) for easier calculations

According to the manual, the tank is 16.5 oz. The conversion is 29.57 ml/ounce.

16.5 oz * 29.57 ml/oz = 487.9 ml of fuel in the tank, round up to 488 ml

2. Figure the oil component of the mixtures

If the tank was full of 16:1 mix then I will calculate how much oil that is by dividing the total volume by the ratio.

488 ml / 16 = 30.5 ml oil in a full tank

488 ml/ 40 = 12.2 ml oil in the tank in a 40:1 mix

Now, subtract the difference between what you need and what you have and that will tell us how much straight oil I would need to add per tank.

30.5 ml needed – 12.2 ml have = 18.3 ml oil to add per tank

3. There are simpler ways to do this, but I will do it again for emphasis to make up my mix per cup.

1 cup = 8 oz

8 oz * 29.57 ml/oz = 236.56 ml in a cup

236.56 ml / 16 = 14.79 ml oil at 16:1

236.56 ml / 40 = 5.91 ml oil at 40:1

14.79 ml – 5.91 ml = 8.88 ml oil needed per cup

4. Convert ml back to imperial measurement (teaspoons)

1 teaspoon = 4.93 ml

8.88 ml oil needed / 4.93 ml/tsp = 1.8 teaspoons oil per cup to make 40:1 into 16:1

I hope that I made my point that sometimes this kind of math can be useable. My points for doing this this way is to protect the machine from excess fuel in the tank and using what I already have have.