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When it comes to fuel efficiency tests, the biggest factor in most cases is weight. The more the weight the more fuel would be needed to haul your vehicle across. This got me thinking, if that is the case, any variant of car, having the least number of features, should ideally be the lightest of all the variants. Therefore, it should definitely help in increasing the fuel efficiency.

So for example, let's take a particular vehicle - SCORPIO-N. It comes in 6 variants which are shown below
Z2
Z4
Z6
Z8 Select
Z8
Z8 Luxury

Let’s remove the models in the middle and just compare the base and the top model

So here are the features in Z8L which are not in Z2







So, an approximate total of 151 kgs, is a huge load to be carried everywhere all the time. Possibly, if we calculate the weight of the extra materials, used for fitting all this, like, wires, fuse, screws, tape, clips…etc, the weight might even cross 160kgs, which is equivalent to 2 healthy men.

Well, I don’t know about you, but I like to drive alone, in peace and surely without the 2 healthy men around :).

Hope this curious mind of mine, has brought up some doubts in yours, if yes, please feel free to share your views.

Agreed with the points laid in the first 2 posts, but it would barely make a difference of 0.5 - 1 kmpl (max) to the overall FE. As someone who anyway doesn't care about FE, please give me all the nice & enjoyable features instead of 0.5 kmpl more.

Although the weight does matter in fuel efficiency most of us don't even consider the same in a buying decision as the results are quite negligible, if one wants a higher variant for the features, one would go for it regardless of the negligible loss in fuel efficiency.

Moreover, in most models, the base variants have a differently tuned engine with lower power and torque as compared to the top-end variants and these also factor in the buying decision sometimes when all these add up, the fuel efficiency of the top-end models can even eclipse the base variants.

For example, in the Brezza, the base variants lost the Smart Hybrid functionality for a while making them less fuel efficient as compared to the top-end, so there are a multitude of factors apart from weight in considering fuel efficiency or a buying decision, but certainly yes, weight does matter for that small 0.5 to 1 km/l increase in efficiency.

I think more than the weight penalty, higher trims are less fuel efficient due to large tyres. Creta base with 16 and n line with 18. Same for many other 10 to 30 lakh models. There is an upside of 2 Rs from base to top in seltos, creta, Harrier (16 to 19 inchers) and many cars. VAG group has difference of an inch only in base to top and so do Maruti models.

It is obvious that more weight will have some effect on Fuel Economy (FE), but the rest of the points are not necessarily true.

This is not all necessarily true. Many of the features you listed are software features (like driving modes, Adrenox Connect, Alexa built-in etc) or hardware features requiring very tiny sensors that would add negligible wights (e.g. Auto-dimming rear view mirror or TPMS).

Further, some of the features that add real weight (like the 4x4 system you mentioned) fundamentally change the behavior of the car and hence the FE is no more an apples to apples comparison.

In short, the base variant and top variant might have different FE for a variety of reasons, and weight might be only a minor factor in it. Keeping aside the special features like 4x4, in most other vehicles, the weights of the top variants and base variants will not be that different to cause a noticeable change in FE.

As already pointed out above, it is also very likely that top variant also has a better tuned engine, maybe even a better tuned gearbox, and as a result, even higher FE than the base variant! And in cases of some expensive and exotic cars, the top variants might even have carbon fiber panels reducing the weight!

Thus, it depends on so many factors and any generalization will not be accurate!

General thumb rule is 10% increase in weight results in 5% reduction in fuel economy.

Assuming these features weight calculations are correct (150 kgs), top variant (2000 kgs) weighs 8% more than base variant (1850 kgs). That is, top variant offers 4% lower average fuel economy than base variant.

If overall fuel economy of base variant is something like 15 kmpl, the top variant will give 14.4 kmpl under the exact same driving conditions. If Scorpio-N gives just 12 kmpl, then actual difference in kmpl or Rupees per tankful will have even lower absolute value.

Not just weight:

• All onboard electronics
• ECU map and the amount of on-the-job training you've given rl:
• Manual AC vs ACC
• Weather
• Your driving on a given day
• Mood and optimism of Multi Information Display rl:

All these are put into play when you look at the practical FE on a given day and time.

Scropio-N is a specific case that has 4x2 and 4x4 in the mix. The official ARAI agency does release FE measurements for the 4x2 and 4x4 variants separately, which differ a lot more in terms of driving characteristics than just the absolute weight of hardware added.

I'm more interested in why you think electric adjust ORVMs, the little sensor for auto wiper and headlamps and especially gloss painted center console add 2kg each compared to the base trim counterparts.

Main difference in fuel economy comes from the width of tyres increasing in higher trims.

If I understand correctly, the nature of engines(read as de-tuned) in base diesel models might contribute to better efficiency? Along with above factors.

Also, I heard from an acquaintance(works in quality department in an automotive company) that there is a grading system for all components in a car wrt QA and components that gets higher score are used in higher variants and components that get just pass score(still acceptable) will be used in lower variants. Is this true?

Its not just the absolute numbers. The overall effect of various factors on fuel consumption varies by a large margin and this miniscule effect of weight gain can be negated by a lot of other factors. Just waiting 10 extra minutes or not on traffic lights will nullify this mileage gain.

I think the numbers are over-estimated by a good margin. Like many others who have made mods on their cars - like LED lamps, projectors etc: We dont see/use of this weight.

Also, many of the features you have mentioned are implemented electronically.

May be you can get the two variants weighed and then check the difference. Or may be check the documentation to find the exact weight difference.

Very interesting thread, never really thought about this on these lines. Surely, if you drive your car for 1-2L Kms then even 1 Kg of extra weight will increase the fuel burn. In the short term however, this fuel burn would be rather insignificant given the efficiency of modern engines, this is more of a long term game.

Yet, I am happy to sacrifice fuel efficiency for certain safety features like Airbags, ESP etc, as these have the potential to save our lives which in reality is invaluable and irreplaceable.

It was for the same reason that Automatic Gear Box usually had lower FE and the Indian car owners were reluctant to move to Automatic. (Higher Upfront cost, higher maintenance cost and low FE Vs Manual).

However, Recent advancements in Automatic gear box, worsening traffic conditions and higher knee cap replacement cost + recovery (Used this one on my Dad) are making people move to Automatic Gear Box.

Similarly, the Stock setup of the cars have improved drastically over the last few years and the R&D done to control the weight has lead to very less additional weight and negligible impact on FE.

Eg. Honda City has a Kerb weight range of 1110 KG to 1153 KG only.

Agree to your point of enjoying useful features than worrying too much about F.E.

But statistically, 1 Kmpl in a car giving 8 Kmpl (average) F.E leads to 12.5% gain/loss :D

Lighter weights of the base models should make them more frugal and eager with fewer lateral movements but also stop quicker. However, it would be too small a difference to notice, but still, there would be an improvement, IMO.