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How much difference is there in fuel economy between a manual and an automatic vehicle and which would be more economic - an 1800cc automatic or a 2000cc manual?

Charmaine

from the "Ask Jack" archives - 14 December 2009

It's a tough question to answer because there are a number of variables. In general terms a manual will always, in theory, be more economical than an automatic. A manual transmission provides a more direct link from the engine to the wheels while the automatic relies on oil pressure and a fluid connection between the engine and transmission to supply the drive. There is always a loss of energy because of the automatic set up which makes the manual better regarding fuel consumption.

Having said that, manufactures have worked very hard in recent times to narrow the gap as most people (especially Kiwis) prefer automatic cars.

As a ball park comparison I would suggest a difference of around half a litre per 100km could be achieved with a manual over an auto if the cars were driven in identical conditions and the same driving techniques were used.

This is where it gets interesting and complicated as driving techniques are the key to saving fuel.

Regarding the question on a 1.8 litre engine being more economical than a 2.0 litre; It would depend on the power to weight ratio in some cases. If for example a 1.8 litre engine was used to power a large and heavy vehicle, then the consumption may suffer or if the vehicle was loaded for a long journey. A 2.0 litre engine may not struggle quite so much and therefore the consumption may be equal or better.