ethanol in gas bad for our cars?

Rice Nuker said
Alcohol has a low vapor pressure for its molecular weight but when mixed with petroleum the solution has a higher vapor pressure because the petroleum prevents the alcohol molecules from adhering to one another to to blocked polar bonds. Does the oil help abate this issue?

The effect you are talking about is a positive deviation from Raoult's Law of partial pressures. Yes, adding ethanol to gasoline increases the overall vapor pressure of the fuel, for sorta the reason you state. But, the physical/chemical interactions between ethanol and a light hydrocarbon in gasoline or a heavy one in an oil is pretty much the same- adding oil isn't likely to change the vapor pressure of ethanol in E10 gasoline.

Rice Nuker said
Is the advantage of oil additive because it adds lubrication properties to your fuel injectors or pistons or valve guides? Is this a desired effect because alcohol reduces the lubricity of petrol fuel?
Does it prevent alcohol from attracting water? Does it increase the caloric content of the fuel? How much oil are you considering to reach what type of result?

Well, the oil-based additives claim a lubricity effect- I dunno. They will not prevent ethanol attracting water, if anything, they may enhance that process. Ethanol decreases the caloric content of gasoline because ethanol has about 39% less energy per unit volume- that's because ethanol is already partially oxidized.