White colored oil indicates water (coolant) in the oil. Gasoline would just dilute the oil and not change its color. Enough gasoline dilution and you could have a serious explosion in the crankcase.
Any radiator shop can check for combustion gasses in the coolant, but they won't be able to tell you how its getting there. Head gasket, cracked head, or cracked block are the usual places.
Pull the spark plugs and look for one (spark plug) that has moisture on it or has a rusty appearance.
Let us know what you find.
John
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