yeah its the viscosity that harms the engine. the reduced flow rate rises the temperature and can also harm the water pump which pumps the coolant. i read that 25:75 mixture results in better cooling of an engine. ideal for summers. rich mixture for colder weathers. i talked to them today morning and they have accepted their fault. i pity all those whose linea runs on concentrated coolant. till date they never used water and said they will follow the manual from now on. injectors cleaning is not mentioned anywhere in the servicing schedule!! strange. how can they miss that. its nice to get them serviced once in a while. my friends honda city's manual says injectors to be cleaned every 7500kms or so. even i made it a point to get cleaned every 20k kms.