Kia Optima: Recommended LubricantsTo help achieve proper engine and powertrain performance and durability, use only lubricants of the proper quality. The correct lubricants also help promote engine efficiency that results in improved fuel economy.
Engine oils labeled Energy Conserving Oil are now available. Along with other additional benefits, they contribute to fuel economy by reducing the amount of fuel necessary to overcome engine friction. Often, these improvements are difficult to measure in everyday driving, but in a year’s time, they can offer significant cost and energy savings.
These lubricants and fluids are recommended for use in your vehicle.

*1) Refer to the recommended SAE viscosity numbers on this page.
Recommended SAE Viscosity NumberOverdrive Clutch Control Solenoid Valve(OD/C_VFS). Specifications
Specifications
Direct control VFS[35R/C]▷ Control type : Normal low type
Control Pressure kpa(kgf/cm², psi)
500.14~9.81(5.1~0.1,72.54~1.42)
Curren ...
Removal
Brake Booster
1.
Turn ignition switch OFF and
disconnect the negative (-) battery cable.
2.
Remove the air duct (B) and air
cleaner assembly (A).
...
Underdrive Brake Control Solenoid Valve(UD/B_VFS). Description and Operation
Description
Underdrive brake control solenoid valve(UD/B_VFS) is attached to the valve body.
This variable force solenoid valve directly controls the hydraulic pressure inside
the underdrive brak ...