A lubricant composition for a direct injected, boosted, spark ignited internal combustion engine that contains at least one non-sulfur-phosphorus containing zinc compound is disclosed. This disclosure also relates to a method for preventing or reducing low speed pre-ignition in an engine lubricated with a formulated oil. The formulated oil has a composition comprising at least one oil soluble or oil dispersible non-sulfur-phosphorus containing zinc compound.

The present invention provides a magnetic viscous fluid and a mechanical device with both improved drag force during excitation and improved rubber-resistant properties. The magnetic viscous fluid comprises a magnetic particle and base oil, wherein the base oil comprises ester base oil and non-polar base oil, and a non-polarity index of the base oil is in the range of 10 to 45.

The present invention provides a magnetic viscous fluid and a mechanical device with both improved drag force during excitation and improved rubber-resistant properties. The magnetic viscous fluid comprises a magnetic particle and base oil, wherein the base oil comprises ester base oil and non-polar base oil, and a non-polarity index of the base oil is in the range of 10 to 45.

The present invention provides a magnetic viscous fluid comprising a magnetic particle, at least one selected from ester base synthetic oil, ether base synthetic oil, and alkylnaphthalene having an alkyl group with 10 to 20 carbons, an inorganic cation exchanger with a siloxane bond, and silicone oil.

The present invention provides a magnetic viscous fluid comprising a magnetic particle, at least one selected from ester base synthetic oil, ether base synthetic oil, and alkylnaphthalene having an alkyl group with 10 to 20 carbons, an inorganic cation exchanger with a siloxane bond, and silicone oil.

The present invention provides a magnetic viscous fluid and a mechanical device with both improved drag force during excitation and improved rubber-resistant properties. The magnetic viscous fluid comprises a magnetic particle and base oil, wherein the base oil comprises ester base oil and non-polar base oil, and a non-polarity index of the base oil is in the range of 10 to 45.

The present invention provides a magnetic viscous fluid and a mechanical device with both improved drag force during excitation and improved rubber-resistant properties. The magnetic viscous fluid comprises a magnetic particle and base oil, wherein the base oil comprises ester base oil and non-polar base oil, and a non-polarity index of the base oil is in the range of 10 to 45.

The present invention provides a magnetic viscous fluid comprising a magnetic particle, at least one selected from ester base synthetic oil, ether base synthetic oil, and alkylnaphthalene having an alkyl group with 10 to 20 carbons, an inorganic cation exchanger with a siloxane bond, and silicone oil.

The present invention provides a magnetic viscous fluid comprising a magnetic particle, at least one selected from ester base synthetic oil, ether base synthetic oil, and alkylnaphthalene having an alkyl group with 10 to 20 carbons, an inorganic cation exchanger with a siloxane bond, and silicone oil.

The present invention provides a magnetic viscous fluid comprising a magnetic particle, base oil, an inorganic cation exchanger with a siloxane bond, and silicone oil. A difference AB between a solubility parameter A of the base oil and a solubility parameter B of the silicone oil is 1.3 (cal/cm.sup.3).sup.1/2 or more.