2.0L Engine vs. 1.5L Engine

[niky]

Like the others have said, there are so many variables that it's impossible to categorically state that all 1.5s are more fuel efficient than all 2.0s.

Older engine designs tend to use more gas. And heavier cars tend to use more gas than lighter ones. I had a 626 with an FSDE engine that got only 5-7 km/l. My Lynx has the exact same 2 liter engine, but it's lighter and the engine is tuned differently, giving it more power, and the Lynx gets 8-10 km/l in the same traffic conditions.

Older carburated and EFi cars are guzzlers compared to newer state of the art direct ignition engines, because newer designs use less gas at idle and tend to be tuned better.

Between a brand new direct injection 1.5 subcompact and a brand new 2 liter compact or light midsized, the 1.5 will typically do 9-11 km/l in rush hour traffic, while the 2 liter compact will do about 7-9 in the same conditions. In terrible traffic, a 1.5 can do 7-8 whilst a 2.0 can do 6's. On the highway, it's more gearing dependent. A 1.5 should be able to do over 20 km/l in "super-tipid mode while a 2.0 should be able to hit 14-16, depending on the gearing and the weight of the car.