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The fuel/oil ratios displayed in column E are baseline values that vary depending on the engine data you will enter. Data entry cells are colored light blue. The needed variables for determining the ratio are the type of cylinder cooling and maximum RPM. To select a different type cylinder cooling just click onto the existing X and press the delete key. Then click onto the appropriate cell and press X and then the enter key. Column F displays the oil cost per gallon of gasoline at the listed fuel/oil ratios. Only the oils that are acceptable for your engine have their cost displayed. Since oil costs vary in different countries the spreadsheet allows you to change its cost per liter in column L. If you only have its cost per quart then multiply that by 1.05 to get the cost per liter. Prices are in USD. Only oils with less than 40% group 1 oil are acceptable for engines with power valves because group 1 oil burns too dirty. Only oils with a viscosity index of 120 or more are acceptable for engines that aren't used mostly at high RPM. There are 19 more oils in the calculator than what is seen from this screenshot:  The ratios displayed are baseline which means you can vary from it although I would discourage anyone from using much less oil than the baseline. I'd prefer people using even more oil for more protection. All air cooled engines should use a low ratio (up to 35:1) so that there is enough oil presence to cushion piston slap when the engine isn't running hot at high RPM. And it is best for peak power for water cooled engines to run between 30:1 and 40:1 but if you aren't racing and want to spend less on oil then just use the spreadsheets recommended ratio. But never use a higher ratio than what it recommends. Below you can see that the spreadsheet has 4 spaces for 4 other oils that you can enter if you know their specs (150C + 200C viscosity). The resultant recommended fuel/oil ratio will display in column E.  |