I have just purchased a "Ratio Rite" measuring cup to measure out my 2 cycle oil.
I would like to run Amsoil 100:1 at a 90:1 mix.
Here's my problem. The cup has lots of measurements.
Pints
CC
FL OZ
And a mix ratio for 1, 1.5, 2, and 2.5 gallons af gas. However, it only measures down to 70:1
What would be the best way to accurately measure a 90:1 mixture. The only mark on the cup lower than the 70/1 mark is 50cc. I'm not sure what my mix ratio would be at 50cc.

My only guess would be to put the cup on a digital postal scale and weigh it. Then fill the cup up to the 50/1 mark. Note the weight increase. Divide it in half to come up with a 100/1 mix. Then just add a teaspoon or so of oil to get close to 90/1.

I guess I could fill the cup to the 45/1 mixture for 1 gallon and pour it into 2 galons of gas. That gives me 90/1 right?
Or, I can fill it up to the 70/1 mixture for 1.5 gallons and pour it into 2 gallons which would give me 93/1 which is acceptable. Am I correct?

Crash90,

Check out the [link=http://www.bmeengine.com]BME[/link] website. Somewhere on the site is a handy chart showing how much to mix for several mixture ratios and amounts of fuel. This should help you out. Good luck!

I found the mixture chart. Its the last page of the users manual. For a 90:1 ratio you need 1.42 oz per gallon of gas.

Yes, I realize that. The problem is that the measure cup doesn't designate 1.42oz.

Oh, then take a ride to whatever store sells kitchen utensils in your area and get a measuring cup used for cooking. They'll get you real close, about as close as your going to get.

A good way to measure oil is with a 2oz syringe.
You can get one cheap at a farm store. Lots of hobby stores stick these too. (Sig brand)
The metric graduations make measuring easier, so I made a chart based on ml of oil.

I love [link=http://hemsidor.torget.se/users/b/bohjohan/convert/conv_e.htm]this site[/link] for making unit conversions.

Maybe others can make sure I'm correct about this since sometimes I have trouble with math. But if you want to mix 90:1, doesn't that mean that 90 parts are gas and 1 part is oil? So that's 91 equal parts? Right?

So by my thinking, you could take the cc equivalent of one gallon, using the conversion site above, and get 3785.4118 cc's in a gallon. Divide that into 91 parts and you get 41.5979 cc's per part. So now you could use the smallest units on your Ratio Rite (cc's) and measure out 41.6 cc's (that's one part). For the remaining 90 parts you just subtract: 3785.4118 - 41.5979 = 3743.814 cc's. Using the above conversion site, you convert to gallons: 0.98901103 Gal. Proving it back: divide 3743.814 by 41.5979 and you get 90 (90:1). It's easy to dispense exactly .989 gallons out of the gas pump.

for 1.5, 2, and 2.5, you can use 62.4 cc, 83.2 cc, 104.0 cc respectively on your Ratio Rite.

When you fill the gas can, you can despense exactly 1.484 Gal, 1.978 Gal, and 2.473 Gal respectively from the gas pump. I hope I'm right and I hope that helps.

Marl Bell

4 liters from the pump here delivers 104 fld ozs![>:] not the 135 fld oz. the conversion states.[>:][>:]
Would be interesting to accurately measure the gas if you are going to be accurate with the oil.

Thanks Guys. I got it figured out.

Don't get carried away with this. One, there really is no need...your engine won't know the difference between 85:1 or 95:1. Second, without the precision equipment of a chemistry lab you'll never get exactly 90:1. I mix a gallon at a time and hese day I tend to "eyeball" the amount of oil I use and I can't tell the difference from when I measured it out.