Pros and cons of diesel-powered motor vehicles

Wednesday March 18 2020
car engine

A 3D illustration of a car engine. Motor parts as crankshaft, pistons in motion. PHOTO | COURTESY


Hi Baraza,

I am considering buying a diesel car for fuel efficiency, preferably automatic transmission. The options are an XTRAIL diesel, a BMW 120D 8AT or a 118D Nissan Quashqui diesel.

Please share your views in terms of their efficiency, reliability and cost of repair.

The car is mostly for daily use to work between Ruiru and Likoni Road. The size does not matter because I intend to have a Forester XT as the bigger car for long runs to my upcountry home.



Greetings, Namesake-of-Pendragon,

You started off by saying that you are considering buying a diesel vehicle and I went “Now, this is a thinking man”; then you added “automatic transmission” and I thought “Here is someone who pays attention to my articles”. You then proceeded to list three vehicles and that is the point I realised I had made a terrible mistake.

I thought you were planning on buying an SUV or 4WD pickup. Turns out I was wrong.

Yes, diesel is good for efficiency. It is also good for torque, which is then multiplied by the wet clutch in the automatic transmission. That is why we love this exact combination in off-road rigs and commercial vehicles. However, in off-road rigs and commercial vehicles, these diesel engines come with, shall we say, a surfeit of cubic inches under the bonnet; which is good for natural power development and an unstressed engine life.

Not so with small vehicles.

I have driven a few small vehicles with even smaller diesel engines and I must say the engineering capability of the builders is impressive, but you cannot run away from the laws of the universe, which is why I am very averse to this type of car, impressive as it may seem. You see, under certain circumstances, diesel engines are rubbish. Let me explain.

Diesel engines may develop a lot of torque for their size, which is a good thing, but the power developed from that torque comes in one large burp before it disappears, which is not a good thing as far as drivability goes. Diesel engines also cost more to maintain, and they come with a turbo (or four) which makes for some interesting developments. Small diesel engines cannot be fitted with large turbos or else they will suffer lag like you cannot believe. So they need small turbos. These small turbos tend to act funny at high altitudes; where the air is thinner and less dense, there is a possibility of over-spooling (the turbo spins too fast), which may sound awesome in theory but is detrimental to the life of the turbo.

There are other attendant complications with diesel engines, more so with those that have direct injection and are fitted with particulate filters (DPFs), which are kind of compulsory in this day and age of environmental awareness - just look up “Dieselgate” on the interwebs for a prime example. These tend to be trouble hotspots if the diesel engine is of subpar quality and/or the owner/operator is unfamiliar with Feeders Off the Black Pump.

Long story short, you don’t really need a small diesel engine. The petrol versions will work just fine – or even better; and the premium you pay at the pump (pun intended) will be quickly compensated for in maintenance costs and outright drivability. Plus, diesel fuel stinks. Now that you mention exclusive city use, then the BMW 1 Series makes more sense than the two Nissans, which are larger and therefore not very ideal comparatively for town use; but then again you mention Likoni Road, which for the longest time has not been in pristine condition, in which case... just save yourself a headache and get the X-Trail.

Mazda, Suzuki, Ford or Mercedes? Help me decide


I previously owned a Toyota Premio (2008 model) 1800cc, which served me pretty well despite the tiresome seat while driving.

I’m doing some due diligence before I switch car brands. I’m considering the Mazda 3/Mazda Axela both 1600cc (what is the difference between the two?), Suzuki XS4 (1600cc), Ford Focus Trend (1600cc) and a Mercedes B180.

Please tell me what you think using the following parameters: purchase price, fuel efficiency, availability of spares, maintenance cost and resale value. I am not closed-minded on the above cars, but a different opinion would also be appreciated considering I have a small family.

Kind regards,


Hello Anthony,

First, the parentheses. There is no difference between the Mazda Axela and the Mazda 3; the name varies according to the market it was initially sold in. Now:

1. Purchase Price

The internet is everything. A cursory look at a hugely popular car-selling website yields the following results:

- Mazda Axela: Sh1 -1.2 million, with a low of Sh960,000 for a 2012 car.

- Suzuki SX4: these are dirt cheap in comparison, hovering between Sh750,000 to Sh850,000 for a 2012 car. I saw one at Sh980,000; sold by someone who clearly doesn't want to let go of the car or is ambitious to the point of being unrealistic.

- Ford Focus Trend: this showed the widest variance and made the least sense in pricing, appearing like the price increases with age, which is not how things work. What am I on about? There was a 2014 car selling at Sh1.1 million (and another at Sh930,000). A 2013 model needed Sh1.3 million to find a new home. A 2012 car seller asked for Sh2.3 million to relieve him of his property. See the pattern here?

But this is all trifling when a cousin of a friend of an uncle of a partner of a client of my company is selling a 2017 2.3 RS EcoBoost AWD version at Sh6.5 million; or the equivalent of six 2014 models. Sure, the list of features on that car is as lengthy as it is impressive, and it packs a 350hp turbocharged motor; but spending the market value of a used Mercedes-Benz E63 AMG (which, with 550hp, has 200 more than the Focus RS) on a tiny little Ford hatchback with a 10-speaker SONY radio will be hard to explain to your wife and friends, even after they hear the sound coming out of that radio. It’s a jungle out there.

- Mercedes-Benz B180: all I seemed to find were 2012 cars and they all cost the same: Sh1.5 million. Some undercut others at Sh1.3 million but what is 200 large here and there when you have already strayed into seven-figure territory? You could get a 2007 car and shave off an entire million from that asking price, which is what I’d do...

2. Fuel efficiency

I keep insisting and will keep insisting this is directly connected to the weight and excitability of your right foot. Keeping all driving techniques constant, whatever small variance exists in fuel economy among the four cars can easily be undone or reversed by environmental factors outside your control, such as traffic density.

3. Availability of spares

Mazda, Suzuki, Ford, Mercedes... I believe all these brands have local outlets, though these outlets sell none of these models, but it never hurts to ask. If they don’t have the parts for these cars, get them on the internet. That said, the Mazda’s parts will be easiest to find given the growing ubiquity of Axela saloon cars compared to the others.

4. Maintenance cost

This will depend on three things: how you treat the vehicle, where you treat the vehicle and what you treat the vehicle with (a.k.a. “point 3 above”).

5. Resale

This is irrelevant. Look at the value the vehicle will bring to your life, not the value you will get when you sell it again, otherwise you’d be a car salesman. If resale value is so important, what happens when that vehicle gets into an accident? Or is stolen? Or repossessed? Or handed over to another family member? What good will resale value be to you then?

Cars depreciate, more so cheap mass-produced white goods like the ones you list. Do not expect a good price for any of those cars after a few years of use: models like the Axela are becoming increasingly common, which means the market will be saturated a few years down the line when you want to get rid of it. Less common models are less common because the demand for them does not exist and there is a phobia of dabbling in the unknown, so expect the market to be thin come resale time, which again means the vehicle will either rot away awaiting an inheritor or you will be forced to dispose of it for next to nothing. What then?

If you have a small family, get the B Class. At least then they get the bragging rights to declare “Daddy drives a Mercedes”, hoping they will not be asked to clarify which exact Mercedes it is, because the B Class does not embrace the traditional values of the Three-Pointed Star.

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