I wouldnt recommend putting it in your engine oil, if youve got any sludge accumulation in your engine it may strip it from the metal and end up in a bearing oil passage or clog your oil pickup screen.. plus im sure it changes the viscosity of the oil and may cause it to break down sooner.

however, it does work wonders when used through a vacuum line. ive also found that a good throttle plate and iacv clean does a very good job. it usually comes in an aerosol can and you can spray it in the passages to the IACV and to clean oil off from around the butterfly valve. i do this nearly daily on numerous differnet cars as part of toyota scheduled maintenance.