Questions tagged [fuel-consumption]

Use for questions related to fuel economy.

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28
votes
6answers
10k views

Do cars consume less fuel when in Neutral? [duplicate]

Imagine we're going down a hill and we're driving a manual car. There are two situations: If I put my car in neutral it will go downhill without any need for the injector to squirt fuel into the ...
22
votes
3answers
5k views

How do the latest automatic transmissions match the efficiencies of manual gearboxes?

Most people know that for old or even somewhat old cars, manual transmissions are more efficient. Recently automatic cars have become almost as efficient or even as efficient as manuals. I was ...
22
votes
7answers
312k views

Is idling bad for your engine?

If I sit in my car for 30-40 minutes with the AC and the car idling, does that "hurt" the engine, or does it simply waste gas and pollute the air? Would it be better if I turned off the car? A ...
21
votes
4answers
5k views

Does flooring the throttle while traveling at lower speeds increase fuel consumption?

I've noticed that in a manual transmission vehicle when going uphill I have two options: Downshift and press the gas more Stay in the same gear and press the gas more I haven't measured it but ...
19
votes
4answers
5k views

At what time of day/temperature should I refuel my vehicle?

I mean, should I refuel my vehicle in the morning? The reasoning is simple, in the morning the temperature is low and the density of the fuel would be higher and I get more energy per litre(or ...
18
votes
6answers
12k views

Will higher octane fuel improve towing power?

According to Will higher octane fuel improve gas mileage? higher octane fuel does NOT notably improve fuel efficiency. Will higher octane fuel, increase power while towing? I looked online and ...
17
votes
4answers
3k views

Are there any advantages of idling a vehicle vs. turning it off and back on again?

I was sitting outside, eating my lunch the other day, and a small bus (you know, one of the short ones) pulled up to the sandwich shop I was eating at. I noticed that the driver got out of the bus, ...
17
votes
2answers
6k views

how to optimize fuel consumption by changing the rear differential ratio?

Is it possible to improve the fuel consumption (decrease it) in my van by changing the rear differential ratio? I would like to optimize it for low-speed driving about 40 km/h (25 mph). Is it true ...
16
votes
8answers
260k views

What can cause a car to consume more fuel?

All over my long driver career, I had 4 cars (5 years). I always compare my fuel consumption with other people who have the same car. 3 times out of 4, I found out that my cars were consuming more ...
16
votes
13answers
253k views

Is the ECON button just a placebo?

I recently bought a Honda Civic that had this in the car: I have no idea what it does, and how it's supposed to help. Even Honda's website is ambiguous, just using a lot of fuzzy words to describe ...
16
votes
8answers
6k views

Is shifting to neutral on a decline more fuel efficient than keeping the gear engaged?

I always had the habit of shifting to neutral on long declines and using the brakes to slow down as needed. Intuition made me believe I'd be saving fuel as opposed to keeping a gear engaged. However, ...
15
votes
6answers
14k views

What makes two-stroke engines less fuel-efficient than four-strokes?

It is a commonly-held belief that two-stroke engines are less fuel-efficient than four-stroke engines, and some example BSFC figures appear to confirm this as well. But what is it that causes two-...
15
votes
2answers
101k views

How much does spark plug gap affect fuel efficiency?

I've read conflicting reports regarding how plug gap can affect fuel efficiency. For example, I've read that too small a gap won't cause a clean burn, or that too large a gap can cause misfires due ...
14
votes
6answers
27k views

How to improve fuel economy in high-mileage car?

I'm driving an 2003 Acura TL 3.2 with 177K miles on it. I bought the car with 110K miles on it. It seems to me that the car is not getting the same fuel economy that it did when I acquired it. I ...
14
votes
4answers
15k views

Does accelerating faster worsen fuel efficiency?

I've often heard that accelerating harder makes for bad fuel efficiency, but have yet to be given a sound explanation of why. Naturally this makes me question this advice. Now obviously when you ...
12
votes
7answers
28k views

Can a car AC unit be run on just the car battery?

This might be a silly question but I was wondering if a car AC unit be run off entirely on battery or alternator? As this could help in Preventing power loss during important times such as ...
12
votes
2answers
31k views

How does ambient temperature affect engine efficiency and fuel consumption?

I remember from my physics class that the ideal-gas Carnot engine is more efficient if the temperature difference between the heat source and the thermostat ("heat recipient") is larger (http://...
11
votes
2answers
3k views

Pulsar 180 - How Can I Measure the Mileage?

Could anybody please tell me how to measure the mileage of my Pulsar 180 bike accurately? I have tried by emptying my tank. I failed miserably, and I had to take my bike walking long distance.
11
votes
1answer
2k views

Brake Specific Fuel Consumption of 2-stroke vs 4-stroke

How much fuel do various types of engines burn per power output? I'm especially interested in naturally aspirated piston engines, and comparing two-stroke to four-stroke. The wikipedia article gives ...
11
votes
2answers
970 views

how can I measure the amount of fuel injected into a diesel engine in real time in a purely mechanic pre-OBD vehicle?

This is a Mercedes-Benz 308D van, year 1992, model 602.316. Pre-OBD, no electronics of any sort, everything is purely mechanical. I would like to retrofit a system which would measure the precise ...
10
votes
2answers
879 views

40MPG at 100MPH?

Around 1987-1988 I had a Ford Fiesta/Festiva. I was in the Army and regularly made weekend trips, driving from southern California to Central Washington a trip of about 1200 miles. I would leave in ...
10
votes
1answer
47k views

How does cylinder deactivation work?

I am still grinning from picking up a 2007 Chevy Silverado 1500 LT 4x4 with the extended cab. 146,000 miles on the clock and 5.3 liter V8 engine. It has displays for everything the engine is doing in ...
9
votes
3answers
60k views

Engine Size and Fuel Consumption

I have this weird misconception that the engine size is related to the amount of fuel being burned in one cycle(4-stroke engine). I know this is stupid but how does engine size relate to the amount of ...
9
votes
3answers
47k views

Is topping up the oil enough of an oil change?

If you use synthetic ester-based oil in a relatively new petrol engine, top it up regularly, and the engine runs very quietly and basically without any noise whatsoever (especially after another top ...
9
votes
6answers
5k views

Fuel consumption at same speed of different engine

I am wondering why two car running at 100 km/h for example with a 100 hp consume less fuel that an engine of 300hp. Even if I take a supercar lighter and more aerodynamics it will consume more. But ...
9
votes
7answers
17k views

Fuel efficiency and Shifting/RPM

I was reading a thread in a car forum where someone wrote: The lower the RPM, the less fuel you use, the less strain you put on everything.. Another person then replied, stating: Not true. If ...
9
votes
1answer
5k views

Does leaving the choke closed increase fuel consumption

I ran out of fuel using my outboard engine the other day, when I had checked the tank beforehand and thought I saw plenty of fuel. I had forgotten to open the choke for twenty minutes or so. My ...
9
votes
5answers
3k views

Will an old engine have worse fuel efficiency than a new engine?

I have a gasoline-engine car that is four and half years old and has been driven for 60 000 kilometers. I have noticed that the fuel efficiency is not what it was when the car was new. However, I ...
9
votes
2answers
18k views

Higher than normal fuel consumption - What could be the cause?

My 1997 VW Golf 3 is over-consuming fuel, I use 10 liters for 45km, My mechanic ask me to change the automatic gear-box because it is not selecting gear above gear 3 I change the automatic gear-box ...
8
votes
5answers
14k views

How to save fuel on downhill slopes on a motorcycle: clutch or neutral?

I have a two wheeler i.e. bike (Honda company, four stroke) which has four gear. While driving my bike, when I come to downhill slopes, I shift the motorcycle to neutral to save the fuel. (The slopes ...
8
votes
4answers
4k views

why do engines have so much unused horsepower?

I've looked at the power rating of an engine used in a Humvee (5500 lbs) and was surprised it's only ~190 horsepower, which is exceeded by many 4 door sedans. So an obvious question is why doesn't my ...
8
votes
3answers
2k views

Would not allowing my vehicle to downshift uphill be fuel efficient?

Would putting my car in Sport and leaving the transmission in 8th gear at highway speeds (using cruise) be more fuel efficient than leaving it in drive with full auto? I just noticed that while in ...
8
votes
3answers
30k views

Best way to repair a rotten fuel line?

I believe the feed line in my fuel system has rotted. If I'm going to cut out the rusted areas and splice a new line in... Is it best to flare a hardline? Is steel the OEM material? How would I ...
8
votes
2answers
882 views

For how long should I idle at a stop?

As I approach a stretch of road that has been single-laned due to roadworks, the sign-flipper spins the sign to STOP. Having been through these roadworks before, I know I'll probably be waiting at ...
8
votes
2answers
648 views

Driving slower at low constant rpms or driving fast to get to destination faster, which saves more gas?

As the question title says. I am a new driver and I understand that driving at higher RPMs can burn more gas faster. However getting to a destination longer would mean you were spending gas at a ...
8
votes
2answers
4k views

Low power, bad gas mileage, smelly exhaust after engine work

My 92 Civic has had low power (need to use at least one gear lower than usual to get the same power) and has been getting bad gas mileage (15-25mpg vs 32-42 mpg usual) since I replaced the head gasket....
8
votes
3answers
11k views

How much fuel does it take to start an engine?

I appreciate this is a question that can't be answered in facts and figures, so I'm after a general idea. I drive a 1986 Supra, which has a modest 2.8-litre engine. I often shut the engine off while ...
8
votes
3answers
4k views

Calculating MPG from MAP sensor (or converting MAP data to MAF data)

My 2002 Honda Accord V6 has a Manifold Absolute Pressure sensor (MAP). I understand that this sensor gives out information in pressure units (psi or equivalent). After doing a bit of research, I ...
7
votes
4answers
2k views

Are there any disadvantage to fuel efficient tires?

I'm in need of new tires and I saw some fuel efficient/low rolling resistance tires. Is there any disadvantage to this type of tire?
7
votes
2answers
14k views

Why does my engine perform poorly and get bad gas mileage after using fuel injector cleaner?

At the advice of someone at a local auto parts shop, I poured a bottle of fuel injector cleaner into my gas tank. This happened around the same time that I had a brake job done and rotated my tires. ...
7
votes
3answers
597 views

Engine Size and Fuel Consumption (cost of driving Audi TTS)

My boyfriend drives an Audi TTS 08 and recently has told me that it costs £15 just for 22 miles in petrol to see me, that's why I apparently don't see him much. When I confronted him about it, he said ...
7
votes
1answer
90 views

Does thick snow considerably reduce fuel economy?

Today there is a snowstorm in Finland, during which I noticed that slow speed driving might require pressing the accelerator somewhat more. This made me think whether driving on thick snow reduces ...
7
votes
5answers
13k views

Can I improve fuel economy by changing differential’s gear ratio?

I would like to use my Lada Niva for normal road travel, but at 3500 rpm at 100 kph it is not very fuel efficient. I don’t know what the current differential ratio is, but I assume it has been changed ...
7
votes
1answer
307 views

Why vehicles use fuel and how can fuel economy be improved?

Why vehicles use fuel? Where does the energy in the fuel go? Vehicle fuel efficiency is continuously increasing. Why is this the case? What technologies car manufacturers are using to improve fuel ...
7
votes
3answers
237 views

Gas mileage down significantly the last few tanks: what should I look for?

The gas mileage in my car is degraded significantly the last three tanks. What should I look for? Details of the vehicle are below, but this question could also apply to anyone who sees this problem ...
7
votes
1answer
44k views

What does a healthy spark plug look like?

The spark plug pictured here: Has some black carbon on the underside of the ground electrode and has black carbon on the "base" area below the centre electrode (not pictured). Is this normal and ...
7
votes
2answers
333 views

How much can sub-optimal octane affect efficiency or power?

Suppose a production fuel-injected engine is tuned for 93 octane fuel. As I understand it, the engine can still run on lower-octane (i.e., less knock-resistant) fuel, but it will pull timing to avoid ...
7
votes
1answer
796 views

Volvo 2.0D engine “self-oscillates” after changing timing belt and adjusting fuel-injectors

I recently had the timing belt and water pump changed on my Volvo s40 (2006 2.0D diesel). The mechanic also cleaned and adjusted the injectors. After the service I noticed that att some rpms the ...
7
votes
1answer
66 views

Gasoline grade manufacturer recommends vs what was used during testing

Toyota recommends to use regular(87) grade of gasoline, but tested cars with the gasoline grade 91(see user manual). Somebody know why they recommend to use grade 87 if they did not tested cars with ...
6
votes
4answers
3k views

Does the tachometer provide any indication of fuel usage?

So, I'm driving along on the highway with the A/C blasting when I notice the price of gas. It makes me think, "what can I do to increase my fuel efficiency?" Some of the tips I've heard have included ...