What oil + filter and petrol do you use for your ek1? general questions

[eeko]

False. Additives are not shit.

Additives in oil are a good thing. But they break down over time.

Thats the advantage synthetics have over mineral oils.

Is that why my car runs a little rougher after 7-8k kms since an oil change with synthetic?

Cause the additives break down and it runs worst?