Another reason I tried 5w40 was the fuel consumption. This was a last resort option since my 2012 swift is giving me about 320-340 kms in 40 liter tank (within karachi). I tried tuning from two separate suzuki 3s, switching to original air filter, new spark plugs (suzuki oem), hi- octane fuel (total, hascol), recharging AC refrigerant, maintaining tire pressures and getting throttle body serviced and injectors cleaned. Another guy told me to get the brakes checked (see if they are not getting partially stuck) and to check the fuel filter.
After oil change, only brakes and fuel filters remain to be checked. If anyone has a suggestion, im all ears. Total kms on ODO are 71000