sir, can you give us the specific car brand/model?

a lot of the resident gurus here can give you some ballpark fuel mileage numbers for the usual 1.5L/2.0L car. pero imho, unless you're upgrading from a relatively old 1.5L engine up to a very new 2.0L engine, baka di magkalayo ang mileage. i've heard some talk about the new 1.6L VVTi engine having comparable mileage to a standard 1.3L engine.

pero kung same generation of cars/engines, if both cars are stuck in traffic, chances are the 1.5L car will have an edge pa rin B)