Synthetic gel is man made and is blended from various chemicals and has molecules that are uniform in weight and shape. Due to the uniform molecular structure, synthetic gel has the following advantages - Synthetic gel is more slippery than petroleum based grease because of the uniform length of synthetic gel molecules allows them to slip and slide more easily over each other. The result is reduced friction and a faster spinning bearing Synthetic gel vaporizes at higher temperatures then petroleum based grease. Synthetic gel runs smoother at all temperatures whereas petroleum based grease forms deposits at high temperatures and solidify at low temperatures. If you use petroleum-based grease, your bearings will eventually gum up.
Synthetic gel has greater film strength than petroleum grease.
This means that synthetic gel is less likely to be pushed out from between two metal surfaces where there's a lot of pressure. Greater film strength protects bearing parts longer and better. Synthetic gel is more expensive than petroleum based varieties but the performance advantages far exceed the cost. Synthetic gel, lasts longer, lubricates better and will give you a competitive edge. In fact, a small gap is present between the inner side of the shield and the outer side of inner race.