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-   -   Base models are more fuel-efficient (https://www.team-bhp.com/forum/indian-car-scene/292118-base-models-more-fuel-efficient-2.html)

On the other side of this: Sports car manufacturers charge > $50k to shave off < 100lb of weight from their Competition/CS/GT3/ST/CSL/Piste... variants over their base variants.

At this price point, a vehicle bought is more for the aspirational need than just the utility. One would certainly aspire to have these features (minus the really unnecessary and heavy sunroof). Thus sacrificing a bit on fuel efficiency.

They may do what I do, and that is chuck out the spare wheel, jack and toolkit from the boot. Tonnes of weight is reduced!

Disclaimer : my cars are 99% driven in the city, and for short distances. Any long drives are well scheduled, and warrant a pre drive engine bay inspection, tyre pressure check and replacement of the boot's contents.

Your curious mind definitely piqued my interest, and so I made some quick calculations.

We recently came in possession of a Thar Roxx AX7L Diesel 4x4 M/T about two months back and it has already seen over 4000km of roads. I mention my car because it would be very similar to yours and let's say it's safe to assume I've driven it alone, with one extra person, two extra and so on... Just for the record, I am an extremely healthy adult and so are most of my friends. We weigh well in excess of the 75kg average you have used in your example.

My observations on the same route around the same time of the day have been that the Thar delivers consistent AFE numbers. I believe that a difference in weight of say 300kgs is way below the threshold for this brute to actually require any additional throttle input. What I am trying to suggest is, whether I carry 100kgs or 400kgs, the thar can pull it with the same minimum throttle input as it makes more torque than necessary very low in the RPM range. So, the difference you are trying to suggest will exist, may apply more accurately to a smaller engine, rather than your torque monster. Just adding to the list of variables from the top of my head.

But let's assume there really is a difference in the fuel efficiency of say 1km/l and make some calculations as follows:

• Assumption 1: Both you and I drive a little extensively and end up doing 1,50,000 kms in 5 years.
• Assumption 2: You get a fuel efficiency averaging 13km/l overall. I get a fuel efficiency of 12 km/l overall.
• Fuel consumed by you = 11,538.46 L = INR 10,86,615 (@INR 94/L).
• Fuel consumed by me = 12500L = INR 11,75,000 (@INR 94/L)

Which translates to about INR 90k over 5 years. At this point, maybe I'll make the money back on resale, and even if I don't it seems like a fair price to have enjoyed the comforts while having owned the car, as it was originally designed to provide. I have a great distaste for the addition of aftermarket electronics. Just my take on this.. Cheers. :)

Sir, sorry, but could not resist myself commenting on this. By any chance do you work in the Indigo Airlines or influence any decisions in the Indigo Airlines. I am asking, as the way Indigo airlines is on the weight reduction drive by removing every comfort material in their Aircraft including seat cushioning, I felt that this though process appeared similar. lol:

Scorpio N diesel Z2 and Z4 variant comes with a hydraulic power steering and a lower tuned engine. The lesser power engine might give a better mileage coupled with a little lower body weight but the hydraulic power steering also takes power from engine. So I don't think there is any considerable difference in mileage between the top and lower variant.

Car fuel efficiency is more dependent on the way we drive the car rather than the weight addition due to feature addition. My dad gets 10-15% more mileage since he is a sedate driver.

It doesn't make a huge difference in ALL cars. The overall weight would be nearly the same.

That said, I got my Brezza top-end ONLY for the 6 airbags. A friend and colleague has the middle variant and the fuel efficiency figures we get are almost exactly the same.

Agree, I think that the weight estimates are way off, would have been easier to just check the declared weight by the manufacturer!

Even leaving the weight out of the equation, modern car features require a good amount of electricity to function which is a differentiating factor.

I own a Ignis Sigma. Whenever I talk with other ignis owners driving their cars in similar roads in service centers, I can always make out a difference of ~.5 kmpl of real world mileage between our cars.

While it's a great thought exercise, but if the weight difference between the base and top variants was as large as 150kg, I have a feeling that we'll even need to do crash tests again. So, while I agree with the hypothesis that additional weight would result in an FE penalty, I don't think the actual difference in FE (between base and top variants) would be large enough to be consistent, repeatable and reproducible.
Having said that, if there's a difference in the tyre profile or width between base and top variants, that I think, would be a more consistent FE delta to look at.

Most base models usually come with steel wheels whereas the top end ones come with alloy wheels which weigh less. So the final difference in weight will be less than this calculation IMO.