Shell Helix Shell Helix High Mileage Oils This range is developed for older, high-mileage engines, and is formulated with anti-wear agents to help slow down wear - helping to prolong engine life. Shell Helix Fully Synthetic Motor Oils Shell Helix fully synthetic oils are manufactured from 100% synthetic base stock and high quality additives to achieve higher performance levels than both synthetic technology and mineral oils. Shell Helix Semi Synthetic Motor Oils Shell Helix semi-synthetic or 'synthetic technology' oils make use of both synthetic and mineral base stocks to achieve higher performance levels that can be formulated from mineral oils alone. Shell Helix Mineral Motor Oils Mineral motor oil is a fraction of naturally occuring crude oil with the right properties for lubricating engines. Shell Helix mineral motor oils help to protect your engine against harmful sludge.