Fuel consumption experiment (Honda Mobilio Gas Mileage Review)

Hi there,

This week, I would like to share the partial result of my experiment regarding the gas mileage of my car, it's a Honda Mobilio1.5L M/T variant Yep, I'm a control freak so I prefer a manual transmission over an automatic one. The results here might not be directly applicable to A/T users. You  might also find some helpful tips on how to maximize the gas mileage for your car.

I travel about 35km to and from work daily and I observed that my fuel consumption varies from 10-14km/L. This of course maybe due a lot of variables like traffic conditions, vehicle load, driving style, etc. Let's define the constant and variable factors that can affect the result. This will also allow us to formulate a definitive conclusion on the results.

For now, let's assume the following as "constant" variables:

    a) Traffic conditions - on the average, I encounter an average of 1 hour of traffic every day.
    b) Load - It's always just me and my car, no passengers
    c) Length of travel - 35km total, to and from work.
    d) Same fuel type  - at least 90 octane unleaded gas.
    e) Same route
    f) A/C always on and on the same thermostat setting.

The variable (w/c I have full control) is just my driving style. Let's define it as mode1 & mode 2. I decided to make this as the variable since I observed that the fuel consumption varies a lot as I shift my driving style. To fully understand these modes, I assume you have a basic understanding of how a car transmission works and the principles behind automatic and manual car transmissions.

These are some of my readings on fuel consumptions.



I wasn't able to take pictures of lower readings (starting from 10.2km/L). I just snapped this every morning as I observed improvements shifting my driving style. I want to be sure on what mode am I really able to improve fuel consumption.

Mode 1:
This is like driving an automatic transmission. The stick is "engaged" most of the time except during full stop. And so, a lot of engine braking is applied. As long as the car is moving, the stick is engaged on the appropriate gear, even in cruising conditions. I observed the "ECO" indicator is on most of the time especially when cruising. This requires less movement of the stick, especially when I'm on the 5th gear already.

Mode 2:

This makes use of the flexibility and total control offered by manual transmission. The stick is frequently disengaged and is mostly on neutral especially on cruise conditions. By disengaging the stick, the car can run up to 80kph w/ the tachometer on idle reading. The car is accelerated to an appropriate speed then, along with anticipation on the traffic ahead, it is either shifted up (i.e, open traffic ahead) or disengaged (i.e. approaching a traffic jam). Also, the RPM is kept at a minimum using higher gear vs speed ratio. The ECO indicator goes out most of the time especially when the stick is disengaged and the tach falls to idle reading (around 750rpm) even if you're still running a good 40-60 kph.

Before I started this experiment, of the two modes, I observed that consumption reading is better (higher) when mode 1 is used since the ECO light is on most of the time. And this is what confounded my  judgment based on my knowledge of how you save fuel vs how the ECU actually computes the fuel consumption. And so, I performed this experiment to confirm. 

As you know, the engine RPM is directly related to engine consumption. The higher the RPM, the more the engine consumes fuel. Since in mode 1, the RPM is above idle most of the time, then this should be consuming more fuel than when it is on idle reading (which is mostly the case on mode 2). I'm not sure of this but maybe the ECU is only computing the fuel consumption when the ECO indicator is on. Using mode 2 and cruising at 60-80kph, the ECO indicator goes out since the ECU thinks you are idle or in a complete stop. But then, the ECU also should also be monitoring your speedometer. Even if the tach is idle, the ECU should be able to assume that you are covering a lot of ground (and saving fuel) due to the speedometer reading.

Here's what I've done so far to confirm whether my assumption is correct or not. As soon as my fuel gauge is almost empty (2 bars left on fuel gauge) I loaded up 25.6L of fuel (1K Php).

I drove the whole time using only mode 2 until the fuel gauge is back at the same reading. Below is the reading of the total mileage covered after consuming 25.6L of fuel.

Doing the math, the fuel consumption is about 12km/L. That is pretty nice already. 

(Better than the figures posted by Carguide.PH on their review of the RS CVT model w/c is at 9.2Km/L only. This may be better compared with the result of the second installment of my experiment. I managed to pump a 17.7Km/L reading on a highway, btw)

I then topped up with the same amount of fuel. This time, I will be driving using only mode 1 until the fuel gauge is back to my baseline. I will post the complete results once done.

Well, that is all for now. I'm pretty optimistic on the full result.

Have a great weekend!

***If you have facts that can help clarify my confusion, please share on the comment section. I'm also exploring other available references (that doesn't add up to how I understand modern engines) and this experiment is part of my research as well.

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Update 8/4/2016

And after weeks of test run, the results are in.
Using mode 1, here is the reading I got using about the same amount of fuel.

Doing the math, consumption is about 11km/L.

That's a difference of almost 25km less during my mode 2 run. In my case this equates to almost a day of fuel savings.

These results of course may vary depending on how the criteria(s) stated earlier can change as well. I can only assure you that the differences are close enough for me to formulate a valid conclusion.

But as per my results, I will continue to use mode 2.

It would be interesting to know how your Mobilio fuel consumption is doing so far. Please let me know in the comments section.


Drive safe everyone.

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