You don't want to use antifreeze just to free up the engine. I don't know why people pay $25 a gallon for fuel. If you mix it yourself it costs less than $10 per gallon. In fact you don't even have to use fuel, you can use methanol which is only about 3 to 4 bucks per gallon, cheaper than antifreeze. But to free it up you only need to open the exhaust port and fill it with fuel, let it soak overnight. No need to fill a huge bowl with fuel. This will not remove burnt on varnish but will remove dried stains. However it may soften varnish so it may be a good pretreatment before using Dawn power dissolver or antifreeze.