Use for questions related to fuel economy.

learn more… | top users | synonyms

13
votes
1answer
4k 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 ...
18
votes
7answers
116k 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 ...
13
votes
6answers
14k 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 ...
10
votes
8answers
1k 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, ...
7
votes
2answers
21k 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 ...
1
vote
3answers
2k views

Fast Idle and High Fuel Consumption

I just bought a Manual 97 Mazda Lantis 323 1.8L DOHC 16 Valve BP and I was amazed that it went through 1/4 tank gas ( about 12.5 liters or 3.3 gallons ) in one day after about 60 kilometers / 37 miles ...
9
votes
6answers
578 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 ...
7
votes
3answers
695 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 ...
6
votes
1answer
473 views

Oily Sludge in the Intake Manifold

When taking off the throttle body to clean my IAC, I noticed that there was a thick layer of oily sludge coating pretty much everything inside the intake manifold: I have two queastions: How did ...
2
votes
0answers
2k views

Fuel Consumption and other Fuel related data from basic OBD-II parameters [duplicate]

I want to know how can i obtain the values of Fuel Consumption, Fuel Economy and other fuel related information from basic OBD-II parameters like Vehicle Speed, RPM, TPS etc. I have noticed that not ...
15
votes
6answers
2k views

Why or why not increase engine efficiency by running the car “fuel-lean” (using a turbo or supercharger)?

Everyone wants their cars to use less fuel, right? I read the following passage about running the car fuel lean from this website: Run the engine fuel-lean, that is, use excess air. It is well ...
14
votes
3answers
1k 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, ...
8
votes
2answers
12k 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 ...
4
votes
5answers
947 views

Can I save money using E85 in my flexible fuel vehicle?

Where E85 Ethanol is available (not very common), the price per gallon is often lower than regular unleaded gasoline. Though I've read that fuel economy is commonly reduced by 20% or more, when using ...
6
votes
4answers
2k 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 ...
14
votes
4answers
829 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-...
8
votes
7answers
8k 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. ...
7
votes
1answer
4k 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 ...
2
votes
2answers
351 views

Mileage varies by driving at different speeds

I drive my car a lot. I do lot of experiments with speeds while driving. Following are my observations: Driving at 60 - 70 km/h gives maximum mileage Driving at 70 - 90 km/h gives good mileage ...
11
votes
1answer
711 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 ...
7
votes
2answers
112 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 ...
5
votes
3answers
5k 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 ...
4
votes
2answers
2k views

Car average mpg display correctness

I have been wondering about the correctness of the average MPG displays on modern cars. Mine in particular is a Renault Modus. What I did is fill the tank, drive around and then refill the tank to see ...
4
votes
2answers
63 views

Fuel Economy Gauge Modification

I have a little digital screen in my dash that re-evaluates my average fuel consumption (L/100km) every thirty seconds. How can I modify this to increase the reporting frequency? Preferably, at least ...
2
votes
3answers
639 views

Is Petrol usage Proportional to Gas Pedal position

I was wondering about this the other day. Is the petrol usage in the car only influenced by the position of the gas pedal? So for example if I take my foot of the gas and coast for 30 seconds, would ...
2
votes
2answers
1k views

Need to know about spark plug

What is the most suitable spark plug for Toyota 3A engine in Asia? (NGK/Champion/denso/BOSCH and also copper/platinum or iridium) Please explain the differences/advantages between them and how it ...