Caltex Havoline available at Petrol Stations is not the Synthetic one, they have stopped selling synthetic, dont know why.
They renamed their CXT line to Havoline.
Previously they were selling Havoline Synthetic and semi-synthetic, CXT was not labelled as Havoline.
ZIC fully-synthetic oil is good for newer cars, if you have an old one with 1 lac kms on it, then go for thicker oil, the best available (and is available since i was 5, i dont know before that lol) is Caltex 5 STAR, great life, keep the engine in good shape, very dependable, buy it from company-operated petrol station, Also its very pocket-friendly !