What really determines fuel efficiency of a vehicle?

Mitsubishi Outlander 2007 model.

Hi Paul,
I drive a 1995 Toyota Hiace Super Custom 3.0L turbo diesel. Recently, the driver lent the car and the person who drove it did not check the water level. It overheated to an extent of the engine shutting down.
The cylinder head and gasket were burnt and some other small parts, which were replaced.
But now the problem is that the radiator consumes so much water and requires refilling everyday after an average drive, which was not there before the incident.
The temperature gauge has also adjusted from where it used to be after an average drive. Could there be problem with it?
Advise me,
Coleb Butungi.

Dear Mr Butungi,
Ordinarily, a vehicle engine should not have its coolant fluid topped up as frequently as you seem to be refilling yours. There is a likelihood that your engine has a coolant leakage which caused the cylinder head and gasket damage in the first place.
I suggest your mechanic inspects the engine block to confirm that the core plugs are not leaking due to corrosion damage. Carefully inspect the rubber hoses and metallic coolant pipes both in the engine bay and in cabin ventilation heating system.
This system uses engine coolant to warm the passenger cabin.

The water pump, thermostat housing and radiator bottom or side compartments should be scrutinised for hairline cracks, which tend to leak coolant when pressurised after the engine warms up. The often-neglected radiator cap should be examined for damage because it serves as a relief valve, which facilitates coolant exchange to prevent heat and pressure build up in the cooling system.
Confirm that the thermostat is replaced with a genuine one rather than eliminating it from the cooling system. To protect the engine cooling system, renew the coolant fluid after the repairs.

Hello,
I read in one of your previous articles that fuel efficiency of a vehicle is not determined by its engine size (cc). You were comparing different vehicles and said a newer one with a 2,000cc engine had more kilometres on the litre than the 1,800cc type. This was eye-opening and is changing the way I gauge vehicles. I have, for example, been driving a Prado 3.0L turbo diesel and it seems to be more fuel efficient than a 1997 model that I drive once in a while. My question therefore is, what is the criteria for finding out the fuel efficiency of a vehicle before purchasing it, because it has become apparent that I cannot rely upon engine size or mere speculation.
Mathew Owomukama

Hello Mathew, the fuel efficiency of a vehicle is not always determined by size of its engine because there are other intervening variables such as the valve train and fuel delivery technology of the vehicle in question.
Ordinarily, the bigger the engine size, the more fuel it should consume. However, development of newer engine variable valve timing technology (VVTi) and fuel delivery systems such as the Direct 4 (D4) or Gasoline Direct Injection (GDI) has improved fuel economy of bigger petrol engines. Innovations in newer diesel engines such as turbo diesel with intercooler or Common Rail Diesel injection have given bigger diesel engines better fuel economy.

Before you buy a new vehicle, ask for the engine specifications to confirm whether it has the newer and more efficient technology mentioned above. Fuel efficiency can also be determined by purpose and size of the vehicle you want to buy. For instance, if your transport needs are for four passengers, buying an eight-seater minivan is not a fuel-efficient decision. Body size and design of the mini van demands more fuel than an ordinary four-seater saloon vehicle.

Dear Paul,
I own a manual Pajero IO 2000 model that has been running well for last two years. It has just clocked 100,000km. But now there is a kind of thudd and jerk feeling on clutch release especially when shifting to gears 2 and 3. What could be the cause?
Denis

Hello Denis,
The kind of noise and experience you describe when you engage gears and release the clutch of your Mitsubishi suggests the presence of a damaged gearbox suspension or mounting. Suggest to your mechanic to check it out. During the inspection, it may also be a good idea to inspect and confirm the condition of the differential carrier mounting bushings.
When they fail, you are likely to get a thud and jerk after you release the clutch after shifts, especially from lower gears. At your vehicle’s mileage, I would not be surprised to find worn out bushings. On the side of caution, carry out the full 100,000 kilometre inspection which should cover your timing belt, fuel filter, all suspension components as well as fluids (engine coolant, gearbox oil, brake fluid) and brakes.

Thank you for technical information on vehicles that you provide. I am considering the Mitsubishi Outlander 2,400cc 2007 model. Please advise on performance, fuel economy, and spare parts. How does it compare with SUVs like RAV4, Toyota Kulger, Honda CRV, etc.
Thanks, Denis

Hello Denis, the 2007 Mitsubishi Outlander is a Cross Utility Vehicle, which combines the attributes of a medium Sports Utility Vehicle and a hatchback saloon vehicle. Its road handling qualities are a fine mix of saloon car like road holding and SUV comfort.

Outlanders’ unibody integrated chassis and body frame combines well with the independent suspension (front McPherson struts and rear multi-links) to ensure good road holding when manoeuvring at high speeds around sharp bends on the highway. This Outlander is spacious and does not feel cramped up like the smaller RAV4 or CRV. Its compact design makes it feel easier to drive around than the Toyta Kluger. The 2007 Mitsubishi Outlander with a 2.4 litre 16 valve DOHC petrol engine is quite nimble and punchy thanks to its MIVEC Variable valve timing intelligent drivetrain, which works well with the INVECS smart Continuous Velocity Transmission. This drivetrain and valve train combination enhances fuel economy (Highway 13km/l; Urban 10 km/l) while delivering an impressive 125 kw of power. The Outlander’s comfort credentials are underscored by its spacious and well thought out interior. The icing on the cake is the seven seat option it offers.

Maintenance will be pricy, especially if you buy a car with over 100,000 kms on the clock. However, what you pay is what you get. In case, you end up with the CVT gearbox make sure it is serviced with dealer-approved CVT transmission oil to avoid damage. Parts supply options are also limited compared to Toyotas. None of your other car choices offer a combination of economy, performance and comfort all wrapped in one package. Denis, follow your heart.