All vegetable oils are 100% fat, and have 900 calories per 100 gramm. It is not possible to reduce an oil's fat content by diluting it, this is only possible with hydrogenated oil (margarine). But low fat margarines are not suited for frying.
When dieting, you have two concerns. First, if you eat more calories than you use up, you get fatter. Second, if you eat just enough, but the weight regulating mechanisms in the body are not in "shedding fat" mode, you don't lose weight. Changing the oil has absolutely no effect on the amount of calories, you just have to restrict the amount of snacks to reduce calorie intake.
The second point could be influenced by oil choice, as different plants deliver oils with different types of fatty acids, and they could have different effects on body chemistry. But discussing such nutritional topics (not the calories count, but the effect of different food on body chemistry) is off topic here on SA, so if you asked more about this, your question will be closed. Anyway, I doubt that anybody here has such information at all. You either need to look it up in a nutritional information source you trust, or just pick any oil. The amount you can consume on a diet is so small that it probably won't make a difference.