Sonet 1.0L Turbo Petrol vs Diesel - Should You Buy The Kia Sonet Diesel?

Update (Feb 16, 2022): Please refer to the latest mileage and fuel cost comparison of the Kia Sonet 1.0L turbo petrol and 1.5L turbo diesel models to help you decide which one is right for you:

Kia Sonet Turbo Petrol Or Diesel? Mileage & Running Cost Comparison

This knowledge will help us objectively answer, once and for all, which engine you should buy and why. We’ll compare the 1.0L turbo petrol engine of the Kia Sonet, which is available in HTK Plus, HTX, HTX Plus and GTX Plus variants and compare it with the Sonet diesel.

Kia Sonet Petrol vs Diesel - 1.0L Turbo Petrol vs 1.5L Turbo Diesel

Let’s start off with comparing the prices of the Kia Sonet 1.0L turbo petrol and 1.5L turbo diesel engine variants.

Upfront Cost - Kia Sonet 1.0L Turbo Petrol vs 1.5L Diesel

The price difference between the Kia Sonet 1.0L turbo petrol and 1.5L diesel options is literally ZERO for the manual transmissions. Since the on-road price will vary from state to state, we are only focussing on the non-existent ex-showroom price difference. But, you also have to take into account the registration fee difference between the variants you’re considering.

Here, we’re going to use the HTK Plus variant to calculate the major ownership costs but these should be proportionately similar for other variants too.

Some states charge a lower registration fee for small displacement engines and petrol engines. If there’s a difference in your state, then replace the Rs. 0 figure in the following table to give appropriate advantage to the cheaper model.

Insurance Cost - Kia Sonet 1.0L Turbo Petrol vs 1.5L Diesel

The insurance costs typically depend on the ex-showroom price of a car. Since the Sonet turbo petrol and diesel cost the same, you might assume that they’d cost the same to insure. And, you’d be wrong. There’s one more factor to consider and that’s displacement. Cars with less than 1000cc displacement have a lower insurance cost than cars with higher displacements. Therefore, it’ll also cost more to insure the Sonet diesel than it’d cost to insure the Sonet turbo petrol.

Expect a Rs. 4,000 - 7,000 price difference in the first year. The difference will also vary based on your selected insurer and add ons you choose. But, for a 7-year ownership period, let’s assume an average of Rs. 4,000 per year as the car’s value will also depreciate with time. So, the diesel car will end up costing you about Rs. 28,000 more for this duration.

Also read - Detailed Analysis - Sonet 1.2 Petrol vs Diesel - Should You Buy The Kia Sonet Diesel?

Performance - Kia Sonet 1.0L Turbo Petrol vs 1.5L Diesel

The Sonet 1.0L turbo petrol is a phenomenal performer judging by its power and torque figures.

The Kia Sonet’s diesel engine, however, makes 20PS less than the Sonet turbo petrol but has 68Nm more torque. If we assume each unit of horsepower and torque as worth Rs. 500, the Sonet diesel gains a Rs. 24,000 performance advantage over the Sonet turbo petrol.

However, there’s more to consider here. The Sonet turbo petrol comes with a 6-speed auto-clutch manual transmission while the turbo diesel gets a conventional 3-pedal, full-manual transmission. This new piece of 2-pedal manual transmission technology is also worth about Rs. 25,000, thus wiping out the diesel’s advantage.

In the real world, both the cars offer great low- and mid-range performance and offer great drivability at city-friendly RPMs. Because they are both turbocharged, they offer a meaty torque and a wider torque band, which greatly minimizes the need to downshift in situations where a non-turbo engine wouldn’t readily gather momentum without a gear change. They’re also both equally capable of cruising at relaxed RPMs on the highway and maintaining triple-digit speeds all day long without any hesitation.

To warp up the performance part, the Sonet turbo petrol engine barely beats diesel with its better power figure and a convenient transmission offering.

Fuel Cost - Kia Sonet 1.0L Turbo Petrol vs 1.5L Diesel

Calculating fuel cost is tricky because the price difference between petrol and diesel varies drastically from one state to another. So, we'll calculate the figures for a 70,000km ownership duration with a price difference of Rs. 0, Rs. 5 and Rs. 10 between the two fuel types. Then you can use the closest figure based on your city fuel prices.

Moreover, the real-world fuel efficiency also varies drastically based on factors like wheel alignment, tyre pressure, vehicle maintenance, driving style, traffic, weather and vehicle load.

To keep things even, we’re going to use the official claimed mileage figures. The Sonet 1.0L turbo petrol with ACMT claims to deliver 18.2kmpl while the Sonet diesel manual has an official mileage figure of 24.1kmpl. There's a difference of 5.9kmpl mileage per litre of fuel between the Sonet turbo petrol ACMT and Sonet diesel MT.

#1 - Rs. 10 Price Difference Between Petrol And Diesel

Let’s say the petrol costs Rs. 90 and diesel costs Rs. 80. With the fuel prices heavily in diesel’s favour, the fuel cost per kilometre tips Rs. 1.63 in diesel’s favour. Over a driving distance of Rs. 70,000, this adds up to Rs. 1.14 lakh.

#2 - Rs. 5 Price Difference Between Petrol And Diesel

If petrol costs Rs. 85 and diesel costs Rs. 80, then the per kilometre cost advantage in diesel’s favour is Rs. 1.35. So, for a 70,000km ownership period, the diesel car will save you about 94,000. That’s still a decent chunk of money.

#3 - Rs. 0 Price Difference Between Petrol And Diesel

If both fuels cost Rs. 80, then the diesel engine’s better fuel efficiency figure only gives an advantage of Rs. 1.14 per kilometre. So, over a course of 70,000km, the diesel engine will save you Rs. 80,000.

Routine Maintenance Cost - Kia Sonet 1.0L Turbo Petrol vs 1.5L Diesel

A turbo diesel engine has a turbocharger, intercooler, high-pressure director injectors and a few other pieces of hardware, which aren’t available in a normal petrol engine. However, here we’re comparing a turbo petrol engine with a turbo diesel engine. So, the routine service costs actually are similar for the Sonet turbo petrol and diesel. In fact, you’ll be surprised to hear that the Sonet diesel costs a shade less to maintain than the Sonet turbo petrol. Here’s the routine maintenance costs of the 1.0L turbo petrol and 1.5L turbo diesel engine of the Kia Sonet:

NOTE: These prices are as per routine maintenance schedule and declared by Kia Motors. GST is not included in the costs. Even without the GST, the above-mentioned service costs should give us a fair idea of how more the turbo petrol and turbo diesel engines might cost to maintain for a period of 70,000km and 1.0 lakh km.

Based on these figures, we can see that the petrol engine will cost about Rs. 1,600 more to maintain for an ownership period of 70,000km.

Verdict - Kia Sonet 1.0L Turbo Petrol vs 1.5L Diesel - Should You Buy The Kia Sonet Diesel?

Except in the fuel efficiency comparison, this comparison has been neck and neck between these two powertrain options.

Based on our comparison, the diesel engine is objectively coming out on top and justifying the price difference with better performance and mileage. It’s saving you Rs. 87,000 during a 7-year / 70,000km ownership period if the diesel in your city is Rs. 10 cheaper than petrol. If this price difference drops to Rs. 5 and Rs. 0, then for the same duration, you will end up saving Rs. 67,000 and Rs. 53,000, respectively.

Objectively, the Sonet diesel seems to make more financial sense if your state has a bigger price difference between the petrol and diesel fuels. However, there are still a few things you should consider:

1. Usage: This is the most important factor to consider. If you mostly drive in the city, especially in bumper-to-bumper traffic, then you might end up appreciating the auto clutch transmission of the Kia Sonet turbo petrol more than others. However, if you rarely get stuck in traffic and mostly drive on open roads and highways, then occasionally modulating the clutch pedal in traffic may not bother you at all.
2. Refinement: The diesel engine will be noisier than the 1.0L 4-cylinder petrol engine while idling and at regular city speeds.
3. Registration Cost: The registration cost for the diesel engine in your city may tip the scales slightly in the petrol engine’s favour.
4. More Driving: If you drive more or intend to hold on to the car for longer, then the diesel engine may turn out to be even cheaper in the long run. We have laid out the cost per km difference for different fuel prices for the two engines to help you calculate the difference based on your expected ownership mileage. Similarly, the table for maintenance costs includes the routine maintenance costs for up to 1.0 lakh km so you can gauge how it’ll affect your bills if you intend to clock more miles.
5. Depreciation: We haven’t included the resale cost as it’s difficult to predict how the market conditions may evolve in this decade. It may drastically affect the diesel cars’ resale price or even increase the demand.

We hope our detailed analysis helps you make an informed decision about whether to go for a Kia Sonet diesel and enjoy lower fuel costs or side with the convenience of auto clutch manual transmission.