Golf 3 have a hard start and later discover that it's mixing petrol and oil. What's the problem

That other answer is suspect , If rings are damaged you will not get compression full stop , you changed head = the head or gasket ??? you should have run compression test just screw into plug socket , If your cylinder is down in compression, it indicates the problem cylinder, It can be due to rings or cracked head or bore , or gasket , come back when you know compression readings , If you have gasket blown the cooling water in rad will mix with oil and show foam . and compression, petrol mixing with oil is due to petrol not cutting off , where is petrol mixing in the sump?

Check the fuel pressure.

Smoke coming from exhaust is sign of a few things wrong. Either the petrol -air mix is not correct and rich fuel mix is going in. Worse oil seal leak. This means engine oil from sump is finding its way into engine cylinders and igniting with petrol. A sign that engine could be damaged soon. This needs to be addressed quickly - piston rings may be loose also.

Without knowing vehicle make or model it is hard to suggest anything further.

diesel motor parts and petrol motor parts are not rely compatible ether use diesel to diesel and petrol with petrol

Bad radiator, blown head gasket.

Hi Marsha, Many people mix brands of oil specified for either petrol engines and the same is true for oils specified for diesel engines if topping up, but it's not a good idea....It is a very bad idea to use an oil specified for one type of engine in the other. I would suggest never mixing oil manufactured for a diesel engine in a petrol engine or visa versa. The reason is that the diesel engine is dirtier than a petrol engine and manufactures of oil formulate it to have more cleaning chemicals than that used in petrol engines....Mixing the two can result in a build up of sludge which can actually block the lubrication system of the engine causing in some cases severe damage. Regards John

Change air filter, oil, spark plug, cable to battery, When changing the oil, there is no need for a new filter. Just wash the old one with carb clean. Held in by 3 small bolts beside the drain plug. Check the rear end oil (90 weight) use the upper plug. Fill till it runs out. Grease the front end. Change the fuel filter. Drain the carb if it is going to sit thru the winter.

HAVE U TESTED YOUR IGNITION

okay start hear turn key three times in a row there should here the fule pump prime ie a whizing noise you may not here this so now check the dash look for engine light it might flash if it dose it might be a code this is stored in the computer in your car .now this is where it gets tricky you need a code reader.but now what is the fact the year of the car and is it flueinjected tbi or carb and what year im not saying im a expert there a lot to go over start with check your manule then all ie oil coolent the right way by the book''''''I think it:is a seneser oil or coolent if the vw golf is 82 or newer but it dose matter what country the is in .in germany from 1975 the vw rabbit was a golf so it would help to know but find vw dealer there not cheep but they know golf I will say this if you smell petrol do not srart the car look for a leak if you find one fix it now dont wait it will cause a fire

try to change the fuel filter first. Then check the fuel pump if it's still good. might need some cleaning since it was not running for several months