dilesh...synthetic oils as the name suggests is man-made...pure n a lot less susceptible to break down in extreme conditions such as high n low temperatures...but normal engine oils on the other hand r natural mineral oils n contain paraffins...they break down a lot faster formin sludge that lines ur engine (thats of course if u dnt change ur oil in time) plus they'r not as protectiv as synthetics...hence the significant price difference...synthetics cost 3 times as much cos they last 3 times as long relativ to a mineral oil's life...thats the difference in a nutshell