As you all know, Fiat recommends an engine oil change every 15,000 km with Selenia fully synthetic. Now in Indian driving conditions ( start stop traffic, pollution and dust , more idling ), is this adequate or should the oil change be done more frequently - like every 7,500 km ? Will this promote longevity of the engine ? Service manual recommends air filter to be changed more frequently if the environment is dusty - no mention of oil change. Searching on the internet mostly recommends oil change at 5,000 miles. What do you guys think ?