@McReggae;

Not quite so categorical.

OD will actually save fuel at ANY speed. Reason is that the vehicle will shift to a higher gear with OD than without.

@Chaka;

It depends on your car. Listen to the engine while driving: if it sounds 'too loud' then you are wasting fuel,if it 'purrs' then you are driving efficiently. Listen to it carefully.

Having said that,once the vehicle is in motion,the optimum RPM will be the one the delivers the greatest torque...check the engine performance curves in the cars manual to get the exact RPM that delivers greatest torque.

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@djinn - If you'd read the rest of my comments,I'd also mentioned that according to manufacturers specs,the MT car would pick up speed slightly faster than a AT. (e.g for 0-60mph: 10.3 for the Toyota Avensis 4Dr Saloon 1.8 VVTi T3-S (03 Edition) vs 11.4 for the Auto version). 15 seconds still seems alot IMHO.

Also were you using an identical car for your 'test'. There's a 1600cc Frontwheel carib which has 161.7bhp (NICE!) and the 4WD carib which has just under 120bhp..



Another useful link on fuel economy: http://www.fuelacademy.com/taylors_tips.html

@majimaji - the Rav4 D4 is the 1AZ-FSE while the corona premio D4 (up to 2001,early 2002) is the 3S-FSE engine. From what I've read online the 3S-FSE is the first gen D4 while the 1AZ is second gen. I think there's a few other engines after that e.g. 2AZ-FSE. The 1AZ-FSE (and probably 2AZ-FSE) is the same engine for the D4 version of the newer premio models.

@simonkabz - i'd be curious too as to the issues with the Direct Injection. My pal with a Mitsubishi GDI says that it could be due to poor quality fuel (+ maybe bad air&fuel filter). Not sure how true that it is but makes sense keeping in mind how the DI engine works.

Also check out this article from (of all places,Uganda's Sunday Monitor).

http://www.monitor.co.ug...ne_all_about_72614.shtml

Very interesting conversation here,lots of facts,myths and lies (or ignorance). We all agree that fuel efficiency relies on several factors key of them being driver behaviour. However,maintenance,traffic pattern,quality of fuel,fuel octane rating,vehicle load,tyre pressure,road surface,tyre rating etc all affects fuel efficiency. Driving a 3 litre engine does not necessarily mean you spend more fuel than your buddy who is drives 2 litre. All the mentioned factors plays a role.

With regard to Manual or Auto,offcourse Auto offers more comfort than Manual but has obvious implications. Most people will complain of wear on the part of the automatic gearbox,which is off course expensive to repair and or replace. Wear of the gearbox points at the driving behaviour/style. The gearbox is meant to last the lifetime of the vehicle,the mistake we make is while driving in traffic,we still retain the vehicle in 'D',thats forward drive. The gearbox is made of many rotating parts,which get damaged because they clash with each other. Offcourse this is gradual process but it does take place and 2 to 3 years down the line,the transmission will not be as good. There is a big difference with the manual gearbox,because with manual gearbox,while in traffic,you only have three choices as follows:

a) Gear is still engaged,therefore the clutch is pressed in,so no clashing of parts i.e the engine is running but its not transmiting anything. Engine power is only transmitted when you start to release the clutch,releasing the clutch transmits power from the engine to the gearbox top shaft which passes this to the wheels to power the vehicle forward or backward.

b) Gear in Neutral,so no clashing of parts

c) You will try to balance the clutch and brake. When you do this,it does not take long before you visit your local mechanic with a clutch problem. If AT,this clutch balancing feature is missing,so lots of things will be going on in the transmission,causing wear. Improved models now have a transmission control module which liaises with engine control module for better cordination but still it cannot eliminate this wear.

If you want to enjoy longer service from the AT,simply observe this ' do not let the vehicle remain in D for long when its not in motion'.

Vehicle technology is very dynamic and now with Tiptronic and or CVT,you can get what you want. My car 'C class',has this feature with 5 speed automatic and 4 speed manual. I chose how to drive it depending on what I want at that time. One can shift from the top speed in D to manual speed,gear 4,3 or 2 depending on driving requirements.

Another important feature is use of 1,2 used with AT. Most users do not know how to use 1 &2. For example,if you are stuck in mud and requires maximum torque,simply shift to 1,you can also move from 1 to 2 just like in manual gearox.

For those driving in very hilly areas and one is descending - going down the hill,its very important not to rely on brakes so much because brakes get heated up and are likely to fade. To ensure you get support of engine brakes,shift transmission to 2 or 3 if fitted

Automatic transmission is the way to go,we have to learn how to use it properly

Hi all,
I have read a lot of stuff on this topic and i have seen a lot of myths being fronted as facts. Being a car freak,let me offer some info to assist.
Fact: Fuel consumption is largely a factor of driving habit,engine & transmission condition,engine design/type etc. more than whether its an auto or manual. Having said that,if all these factors are held constant,a manual has offers better/more horsepower,torque,acceleration,fuel economy than an auto. Check the figures on car specs and you will see a significant difference.
However,an auto is easy to drive hence its popularity.
Also,O/D in a car is overdrive,meaning access to a higher gear (like gear five on a manual) which leads to greater fuel economy,not greater power. On the other hand,some cars do have a power and/or hold button. The power one allows higher revs and max on teh torque curve of the car hence high acceleration. The hold button 'holds' the respective gears a bit longer. These buttons grants the transmission to max on the torque and/or revs hence giving better performance. The tiptronic system gives the best of both systems i.e. it allows the driver to change gears at their whim while also being 'clutchless'.
I hope that helps clear matters a bit.

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Rule No 2: NEVER Forget Rule No 1!!!

Doing neutral downhill am told destroys the AT gear box.Just drive downhill with it engaged.The vehicle has a computer to assist in power saving.

@ Mkimwa - best of luck with that ... being a Japan market vehicle, very hard to get. Been looking for a while with the corona premio 2000.