Ok,my mum messed up my dads car....

Only 20 ml? You can top it off with the rest of the bottle, add in some tranny fluid, engine oil, and then maybe the lead substitute. If it's a slant 6 or a small block it'll be fine!

Quick story: One time I guy I know with a slant 6 pickup was running low on fuel and he put in about 10 litres of diesel fuel by mistake. Before he started the truck I noticed his mistake and I laughed like an idiot for 10 minutes. Then I stopped laughing when he asked me for some cash so he could top off the tank with some gas. Well, he put in another 25 liters (gas this time) and it ran a little smokey for the next little while, but that slant burned off the diesel no problem. He was probably runing about 30 litres of gas to 10 litres of diesel that week.