@popi, there are so many variables one needs to look at beyond engine capacity....you will find (as was illustrated on SK recently while the passat debate was t its peak) that even if you take two different 1800 cc cars, the results are different.

Some variables, IMHO:

1 - Vehicle weight - I find my 1796 cc rather sluggish because of its weight vs BHP ratio and sometimes it can be outrun by a 1500 cc g-touring (i.e. an overpowered beer can). If you took a Mercedes Actros (without a trailer) and a BMW 725 to Runway 1 at JKIA, the Actros will invariably outrun the BMW at some point...
2 - Body type and aerodynamics - I do not think an landrover with 3000cc can outrun a toyota mark II.
3 - Tyres - not just the tread (or lack thereof), but the width i.e. if a tyre is 14x80x185...its the 185 I mean - not the profile (80)... - I see may people rushing to upgrade the width from 175 to 195 (or 195 to 225) - this increases drag where the wheels meet the road (but the upside it offers greater stability on corners, defensive swerving, etc).
4. Driving habits - staying too long in a low gear - if you gave two people the exact same cars with only 10 litres of fuel and ask them to drive down Mombasa Road at midnight, when traffic conditions are the same for both, one will invariably get further than the other. Staying too long in a low gear, revving too hard on acceleration (like matatus), harsh "start stop" motoring. etc
5. Driving Speed (this may either be dictated by traffic conditions or driving habits) - there is an optimum speed (abt 80-90kph) when consumption is at its best....push it ober 100 and MPG starts to drop. Crawl along t 60kph and its still inefficient,

Sorry I cannot comment on EFI, WFI, etc...
My three optimistic 2010 naira....

How about diesel versions? Me thinks there is little difference among the various eng. capacities e.g. the vx-4200 cc and the noah-2200 cc dithoro wont give a very different milage (~12 kpl) kweli?

@Djinn has captured the key variables


... throwing in my thoughts:

Another variable might be the terrain - I've found that driving down to MSA from Nairobi is potentially cheaper per km than up towards Naivasha, Nakuru since the road is flatter.

Torque vs HP:
low rpm for a max torque from what i've read up (being doing a lot of that lately) generally translates to better consumption for that engine capacity. Typically diesels have max torque at < 2000 rpms. However, I've seen a good number of petrol engines that have max torque from like 1700 rpm - (was looking at the VW engines at this time). Many petrol engines typically have max torque at a pretty high RPM.

@ noinvestor If you have 2 corolla nze with different cc or as you say 'all things held constant' for sure higher cc equals more consumption

>>> generally true. though the way people drive is fascinating to watch.

Many people hardly service their vehicles as well.

@simonkabz

That VX is HEAVY!! - 2.5 tons should consume more than that i think. almost 1 ton heavier than the townace.

Incidentally I've done 14 km/l with a full compliment of passengers + a large sack in the boot on a 2L petrol. - for a VW TDi that would be nothing to write home about though...

@mukiha goes to show that we could save quite a bit in our economy if all roads were smooth

Very interesting discussion. Driving style therefore is a key factor. I find that in a manual car, I tend to go to gear 5 maybe twice or thrice as fast as many guys I've seen... and nowadays I try to keep to 80 - 90kph, maintaining RPMs of slightly under 2000. However, traffic jams just jumble up everything. I see the benefits on long trips, though.