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The Dutch, Scottish, & Indian people megathread (Driving economically)


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Fairly sure it's been proven that coasting downhill in neutral uses more petrol than leaving it in gear.
 

The one thing which I've always wondered is whether it's better to be cruising at 60km/h in fourth, or fifth, as most modern cars are geared to cruise comfortably in either. The tradeoff here is revs versus manifold vacuum.

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I'm getting about 16l/km  edit: 16km/Litre( 6.25l/100k), but that economy is a total lie because I'm also running 25:1 on 2T oil at ~$50/l. So around ($1.98 / 16km  fuel + ($50/16,/25)) = 12.375c/km fuel and  ~12.5c/km for 2T? (LoL, just realised).

 

A reliable friend who was watching his economy closely in a subaru and an audi said he got better $/l out of the BP 98 octane, because although it cost more per litre, the engine ran lower l/km. Unfortunately I'm not reliable, and cannot remember which of those vehicles that conclusion belonged to.

 

edit: Oh, and a McLachlan of the clan McLachlan, checking in. 

 

You spendthrift wastrels.

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Fairly sure it's been proven that coasting downhill in neutral uses more petrol than leaving it in gear.

 

The one thing which I've always wondered is whether it's better to be cruising at 60km/h in fourth, or fifth, as most modern cars are geared to cruise comfortably in either. The tradeoff here is revs versus manifold vacuum.

 

 and brake boosting, so yea I don't think anyone will agree with N is a good idea at any time in any car

 

the basic's are there, weight (less is good) tires, and calm driving & coasting to stops not hard on the brakes when you get there

 

edit : McRobert's checking in too and mums side is Maori so liek the Billy-T sumed it up we dont like paying for anything either

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Fairly sure it's been proven that coasting downhill in neutral uses more petrol than leaving it in gear.

Depends on the car, but largely, yes that's correct.

In my experience it's a fair bit of a gradient before it equals the engine braking though, I guess I was more meaning fairly gentle downhill bits.

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 and brake boosting, so yea I don't think anyone will agree with N is a good idea at any time in any car

 

Brake boosting and PS etc all work perfectly fine in neutral.

Even if your engine is off for some reason, you would get about 3-4 full pumps on the brake before you run out of booster.

It's becoming more common for cars to have electric PS as well instead of running from a belt on engine.

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The one thing which I've always wondered is whether it's better to be cruising at 60km/h in fourth, or fifth, as most modern cars are geared to cruise comfortably in either. The tradeoff here is revs versus manifold vacuum.

That's where it very much comes down to the particular engine. 

Probably less of an issue on modern VVTI motors buutttt

 

The relevant term here is BSFC (Brake Specific Fuel Consumption) 

Basically an engine has a sweet spot where it makes the most amount of power, for the least amount of fuel used. (Based on both rpm and vacuum)  

So the closer you can get to your engines point of best BSFC the better.

However since they generally dont give end users a BSFC map with your car your best bet is just to check with OBD2 or whatever.

 

Looking at this example here, the best power for fuel used would be found by holding the engine at the smallest "island"

Not sure what this graph is for but maybe a generator or something that's designed to just be held at max load at 1500rpm.

Some car engine BSFC maps that I've seen will have the "island" at say 2/3rds throttle and 4000rpm or something like that. On a VVT engine you'll find that the lines are further apart because it holds better efficiency through more operating conditions. So 3rd or 4th gear might be in the same efficiency region.

 

energies-08-03225-g004-1024.png

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Some of the crappy old shitters I drive will wear out their gearboxes prematurely if you coast in neutral excessively.

This is due to the speed difference between the mainshaft and layshaft and means that the mainshaft doesn't get lubricated properly. This is only really a problem with primitive gearboxes though.

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Around town I get about 6.5 L/100 km if I drive like a granny and put it in 5th as soon as possible.

 

Open road between 5-6 L/100 km, usually driving 100 km/h with a window down. I could probably get it down to 4.5 if I drive 80, but I don't want to hold up traffic/Starlet is pretty boring at 80.

 

These values take into account my odometer error of 7%.

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Thinking about it, the right units would be $/km, right?

 

I assume we're talking about getting best economy from the car we've got, as opposed to discussions about the VW supereconomy intermittent cycle hybrids from last decade? (Which is an interesting beastie. A supercar, with the super on a different axis).

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You don't have to baby your wagon along to get some sweet mpg, just a little bit more situational awareness as to what the road/traffic conditions are like ahead.

 

Case in point; When shifting the brother in law from Auckland to Ohope, I drove his Maloo with a shitload of stuff in the tray. He drove his Octavia, again packed to bursting point and the wife drove her car.

They know I'm always trying to reach a new personal best in mpg and give me shit about driving like a nana...

All set off at the same time, and I arrived in Ohope about 2 minutes after they did - despite the fact I'd stopped for a dart and taken a slash. 

Dash read-out in the Maloo showed 8.0L/100km and filling it worked out at 8.1

 

I bailed on a game of chicken with the fuel gauge in our Superb recently, I swear the needle was beginning to bend since it was already pegged on the E and it said I had 50km left.

Still, 1200km on a $42 fill was more than adequate...

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I recently picked up a 1997 Hilux with 22r engine as a work vehicle.  

 

Initial driving was pretty terrible, very low power, flat as under full throttle.

 

1st couple of tanks of fuel i was getting about 370km out of 50l of petrol.  7.4km/l or 13.5 litre per 100km.

 

So far ive removed the old rusty cat converter and replaced the front part of exhaust, leaned out the idle mixture screw (im pretty certain this only affects idle, nothing else), and its gone from idling at 12.8 : 1 to 15:1, and is around 13.5 at light to moderate loads, but is still 11.8 : 1 at full power.

 

On the weekend i removed the massive air stirrer on the front of the engine, as the viscous clutch was seized and fan was running at full speed all the time, and fitted a really decent elec fan.  It sounds way better now, and has a little bit of character, can rev out a lot better, and has way better throttle response and seems to have a lot more torque.  

 

On this tank (Z 95 octane), ive so far done 420km, and its not empty yet.  Im not sure where to go next, but looking at the secondaries and why its running turbo spec fueling is the next step, but need to pull the carby apart to adjust jetting if thats the case.

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Alfashark.

Wow that's amazing!

modern cars give incredible MPG.

 

I have a shitty 1992 Sentra station wagon on dedicated LPG.. 

It does 530 km or so to a 53L tank, much better on a long trip. I drive it like it's stolen.

Seems pretty economical for a $1200 car, LPG is $1.00l plus GST.

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Agreed, there's been some serious advances in the last 10 or so years.

 

The bro-in-law's Octavia could still be pedaled down to 6.0/100km, which is fuckin outstanding for a 1.8L 20v turbo with over 300,000km on the clock and it's been re-mapped to around 225hp for over 200,000 of those.

The sweet spot for the BSFC in that car, both prior to and after the re-map was 5th gear and pulling just on 3k/rpm at 115-120kph on a GPS.

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Haha..  I spent about 6 months monitoring my fairmont when I first got her, with a 2.9 rear she got about 28-30l/100km combined, driving like an absolute gran seemed to make no difference.. when I changed it to a 3.9 rear it got worse and went to 30+l/100km combined. My missus drove it as a nanny car to work and back (7mins away) with the odd local trip and used half a tank a week in gas at $1.20 a liter..

 

shit was awesome, and when I finally get her on the road she'll prob stay in the garage anyway because Rena

 

on the other side, had a Vtec domani the was frugal as fuck at about 5.2l/100 highway about 6 city.. 

 

hilux doesnt move from 10-10.5l/100km city or h/way unless you really give it to it, but normal driving/frugal no noticable difference

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