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On 5/22/2021 at 11:31 AM, UCyborg said:

2001 Volkswagen Polo with 1.0 petrol engine.

On 5/22/2021 at 11:31 AM, UCyborg said:

Mine is about 6.3 liters

I eventually picked up the habit of cruising at 110 km/h rather than 130 km/h on the motorway and that reduced the fuel consumption to little over 5.7 l/100km on that model.

That 4.5 l/100km figure is on the current 2022 model, after recently experimenting with cruising in 90 - 100 km/h range. Slower indeed gets you further.

Some time ago I stumbled upon this comment on YouTube, forgot which video:


A much better idea that has been proven to work (about 10% better gas mileage) in a regular gasoline engine car, is to accelerate briskly and then coast for a reasonable amount of time and repeat (if traffic allows). This is especially beneficial in low traffic conditions. Ok now for the details... Suppose the speed limit on a road is 50 MPH and you are at a red light with light traffic, instead of accelerating gently, which many people tend to think if fuel efficient (but really it is not), accelerate briskly and even 5 MPH over the speed limit (cuz it will only be briefly), then let the car coast down to 5 MPH under the speed limit and repeat (provided conditions allow). So basically you will be "bouncing" between 45 MPH and 55 MPH in this example. That is about 10% more fuel efficient to do that (especially is low traffic conditions) than if you went a constant 50 MPH. Since u r a mechanic, you probably already know what I am about to say next but I will mention here for your other readers... a typical gasoline internal combustion engine is MOST efficient (power output to fuel consumption ratio) at about 75% of it's maximum output power. For example, a car with 200 peak HP is most efficient when it is outputting about 150 HP. That is one reason why accelerating briskly helps save fuel. The other necessary piece for save fuel is the coastdown. Notice on cars with instantaneous fuel MPG displays that when you get off the throttle completely, the instantaneous MPG goes up to about 99 MPG. So think about it, if you accelerate briskly and get 10 MPG or less but then coast and get 99 MPG, it helps the overall mileage vs. driving at a constant speed. The best way to prove this is try it on a car that shows average MPG. Drive the same path using both techniques, the "standard" technique and the fuel efficient technique described here. You should see about a 10% improvement. Make the path more than about 5 miles otherwise it might not be enough to get an accurate reading.

That, I haven't experimented with. Those that encounter me on the road must already think I'm insane as it is. But, I get to listen to the music longer!

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I learned the speed-up-then-coast back when "hypermiling" was a big thing.

One of my "favorite" things to do is see a RED LIGHT over half a mile up the road and take my foot off the gas and coast the entire half mile.

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  • 4 weeks later...

Something I've been wondering about, this car has EFB+ battery installed. There's not much written about the plus part, seems to be a Volkswagen thing, they only have written on one of their sites that it has surface-active carbon additives for more effective power consumption and charging capacity. But carbon additives are mentioned at other places for EFB (without plus)...

The main part, the car keeps the battery charged at 80% max, supposedly to save fuel and reduce emissions, something about alternator not being run all the time by the usual means, but engaging when using engine for braking and using kinetic energy to run the alternator. I've noticed with the help of diagnostic interface that when the car is sitting for a day, battery discharges from 80% to 72%. That's a whooping 8%! The manual does mention something about shutting electronics down if it goes too low, but nothing specific, just that it can't prevent battery from going empty if you do something stupid like leaving the ignition on with the engine off.

So about EFB's longevity, while it's designed to operate better at reduced state of charge, I wonder if it would still be beneficial long-term to charge it every once in a while, given that the car is mostly sitting in garage for weekends and a week at a time few times per year.

Edit: Higher state-of-charge should still be the better state to be in.


Edited by UCyborg
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