@kanda,u r spot on. Selecting OD OFF while cruising essentially disengages gear no 5 (correctly referred to as the overdrive) n the thing simply shifts downwards to gear no 4. This can also be achieved by simply flooring the accelerator. The effect of the OD is therefore ONLY noticeable at speeds above 80kph. Driving in town with the OD OFF is the height of ignorance,there is no effect as the speeds r low hence lower gears. A simple rule of thumb,when driving any car,ensure the warning panel lights are all off,including the OD light. @mburu,ensure the premio isnt 2000cc /D4 engine.

The only reason why some people are still alive is coz its illegal to shoot them!!

@simonkabz & @kanda; you are both spot on.

The greatest factor in fuel consumption is not the size of the engine,nor the transmission system (auto/manual/4wd/2fwd/2rwd Awd etc)! It is in the way you drive!! Consider this: they who delivered my Mazda Familia 4wd AT from the port to Nairobi consumed 60 litres of fuel on the journey. When I go on holiday to the coast with the car nearly fully laden,I consume about 40 litres on the returm journey.

Same car,same trip and one driver takes 50% more fuel. And dont say that he cheated me. No,he's my buddy and I know how he drive....he imagines he is Shekar Mehta!!!

On this overdrive thing: it is confusing....in some cars it is labelled OD and in others it is labelled LOCK.

If your car is labelled OD:
Engaging the overdrive means that the car will automatically shift up to one gear ABOVE that set on the lever. Thus if you place the lever in position S (1),then the AT will shift up to gear 2....and when the lever is in position D (3),the AT will shift all the way to gear 4 [not labelled on the lever].

Disengaging the overdrive means the car will not exceed the set gear...infact you can drive it like a manual car starting from gear 1-to-2-to-3. However,the gear ratios of an automatic are very different from those of a manual car...gear 1[auto] is equivallent to something like gear 0.7[manual] and gear 3[auto] is equal to approx gear 3.8[manual]!!

If your car is labelled LOCK
When you engage the LOCK,you lock the car in the gear sellected on the lever...it will not shift up or down.....a very useful function when driving in heavy traffic,up steep hills,when stuck in the mud etc

When you disengage the LOCK,you release the gears and the car will shift up to one gear above that set on the lever [this is equivallent to engaging the OD]

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When driving an AT in normal conditions (no heavy traffic,no steep hills etc),you can save a lot of fuel by 'forcing' it to shift upwards earlier. You do this by releasing the accelerator momentariry and then pressing it down gently [not to the floor!!!!!!]. That way,you get it to gear 4 at about 50km/h instead of the 100km/h if you leave it to decide.

But; if you love your speed and quick accellerations,then you shouldn't be discussing fuel efficiency - whether the car is MT or AT!!!

Behind the gardens...Behind the wall...Under the tree (Including: Red...Dark Blue...Yellow)

@Kanda,

We are essentially saying the same thing.Taking off O/D simply means that you are shifting the car to the next lower gear thus giving yourself more power at hand (or is it foot?).

@Mukiha,

True most A/T GBs have four levels .,but there are models with higher levels.The highest this far would be the Merc G7 A/T gearbox with 7 levels



Yombo dhier....!!

@Njunge and Tuvok - then how come I have been able to outrun an Toyota Carib (travelling together),plus various other automatic cars (i.e. men under the influence naturally behaving badly) - esp from a standing start - ok I agree most times I have had a few cc on them but sometimes its dead even. Maybe I am burning fuel too rich?



The problem with equality is that we desire that it be with those that have more than us rather that those that have less

What is the optimum engine RPM for good fuel efficiency?

@Chaka - RPM will depend on engine and gearbox size. While both a BMW 520 and a Mini 850 will both idle at 800-900 rpm if you tried to reach 60kph in gear one in the mini (i.e. very high rpm like 3500rpm roughly because of high gear ratios) you would spoil the engine. But you could even get t0 60kph in the BMW at a lower RPM (i.e low gear ratios)

The problem with equality is that we desire that it be with those that have more than us rather that those that have less

@ tuvoc,
I'd say your D4 premio performs similar to mine. I've floored it to nairobi - malindi and it did 14km/l and for town running it does over 10km/l.

@simonkabz,what have you heard about this engine? I'd like to be forewarned.

Is this D4 engine similar to that of Rav4?

In man prudence,in woman patience - Jacob Cats