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11

letting the car idle isn't good for the car, especially with the AC on. What you're basically accomplishing is aiding in the car wearing without racking up any miles. With the cylinders firing, you are using several electrical components, putting some small amount of stress on the belts, etc. If you've ever seen ads for cars claiming high mileage but ...


9

No, the tachometer can not be related to fuel efficiency as the tachometer is measuring the amount of rotations per minute (RPMs) of the engine. In the same gear and at the same speed your tachometer will always be at the same RPMs. However, you can be at 2000 RPMs and be barely touching the gas pedal (or completely off of it) because you are coasting down ...


9

The key things you can to to keep your fuel economy: Keep it tuned up: for spark plugs and wires, go with the manufacturer recommended brands/default ranges. Additionally, you'll want to make sure you change the oil regularly, as sludgy oil will rob your motor of efficiency. Finally, a clean air and fuel filter will also go a long way to imrpoving fuel ...


9

This is an easy experiment to do: Fill your tank with unleaded. Drive a well-known standard route. For example, my commute is almost always the same from day to day. Drive to gas station and re-fill the tank with unleaded. Note amount filled and cost. Take the total miles driven from steps 1 - 3 and divide by the number of gallons filled in step 3. ...


9

Holding the clutch in is generally not a good idea. The clutch is designed to be used for very short periods between gears, and for holding in first when you are about to pull away. So if you are wanting to coast you should definitely do it in neutral. The difference between these two from a fuel consumption perspective should be marginal. From a safety ...


9

In a word: No. To add more to it: Absolutely Not. There is one huge thing which you have not taken into account. That being carbon which deposits from the air/fuel mixture burning process. Where does it go? Right into the oil (among other places). A small amount of blow by occurs which also forces this mixture down into the crank case. Now you have it in ...


8

Any tyre design is a balance between cost, grip, longevity, water displacement and rolling resistance. Change one, and chances are you'll adversely affect the others... Personally, I would always put grip and water displacement (which affects wet grip) above all the others on a priority list. The difference between those "fuel efficient" tyres and normal ...


8

You are driving a Saturn S-Series (My car for the last 8 years, which I am very happy to have.) You should definitely have much higher fuel economy. (19.6mpg is what you have. 33+mpg is easily achieved.) I would hardly be surprised if it is the ECTS (engine coolant temperature sensor.) These plastic temperature gauges fail with about 100% certainty. This ...


7

Aside from financial and environmental considerations, U.S. and Canadian governmental agencies say that idling produces various negative effects on engine components. During idling engine does not work at its most efficient mode, and the fuel combustion is incomplete. That leads to glazing of combustion chamber and reducing effectiveness of spark plugs in ...


7

The short answer is that yes, you can change your differential to optimize fuel efficiency. CAVEAT: it is almost certainly not worth it. Here's a very high level discussion of why there are better ways to achieve the same goal (better fuel efficiency): Think about how the air-fuel mixture in the engine is managed: for each revolution of the engine, a unit ...


7

As I said over here, mileage calculations are pretty easy: Fill your tank. Drive a well-known standard route. For example, my commute is almost always the same from day to day. Drive to gas station and re-fill the tank. Note amount filled and cost. Take the total miles driven from steps 1 - 3 and divide by the number of gallons filled in step 3. That's ...


7

The root problem here is that you are conflating several different terms. See Wikipedia for a calculation of horsepower from torque (tau) and rpm (f in this equation): If you assumed a flat torque curve, you can see that peak horsepower would continue to increase with RPM. In fact, if you wanted to increase your marketing horsepower for a new vehicle, ...


7

The most common causes (aside from poor driving habits) are bad timing bad sparkplugs low octane fuel* malfunctioning coolant temperature sensor blocked catalytic converter(s) malfunctioning MAP/MAF sensors driving with the parking brake engaged** having aftermarket wings on the car. tyres not inflated to the recommended pressure and a few others I can't ...


6

As a bald indication without other context, no, the tachometer is insufficient to tell you much about fuel efficiency. Your trip odometer and fuel gauge are your only truly useful (and built-in) measures. Reset the trip after a fill-up and make a mental note of when you hit the 3/4, 1/2 and 1/4 marks on the fuel gauge. While the fuel gauge might not ...


6

With regular driving the Air/Fuel ratio is kept constant at 14.7:1. So if a larger engine needs more air (more swept volume) per cycle then yes it will require more fuel. So the question boils down to which engine has more friction per cycle, and which car has more weight to carry around. The friction is measured in FMEP (friction mean effective pressure) ...


6

Some good points have been given already especially as far correct spark plugs and correct fuel go. Some other points, unfortunately, I can only describe as regurgitated 'car-care' sales drivel. I'm almost surprised that no one has mentioned that you should wax your car more often. Here is a list of things that are not worth your money and time: Changing ...


6

You should not notice any difference. Here's why: 1 hp = 746 W. This means that 60 W is 0.08 hp. The worst possible scenario from a load perspective is at idle. Assuming the engine is outputting a measly 5 hp at idle, the extra load would work out to 1.6 % of this value. The change in fuel consumption is barely sensible.


5

There are 4 major types of Evaporative Emissions from the fuel system of a car, these are: Diurnal: Evaporation caused by the fuel tank being heated by the sun Running Losses: Heat from the engine and exhaust system causes fuel vaporisation Heat Soak: Once an engine is stopped heat from the engine and exhaust system causes fuel vaporisation Refuelling: ...


5

Assuming the bus has a diesel motor, the answer is yes. As an old German Mercedes mechanic told me, "with a gas engine, the primary contributor to wear is hours of operation but with a diesel it is the number of times it is started". What that really means is not the number of times you engage the starter motor but the number of times the motor is heat ...


5

This is more complicated than a simple ratio. I present as evidence exhibit A: the comparison between the BMW M3 and the Toyota Prius on the Top Gear test track. In short, the Prius was driven at its top (not very high) speed and the M3 remained right behind it for ten laps. The resulting fuel economy results were: 17.2 mpg Prius 19.4 mpg M3 That's ...


5

Your question has a few unconnected points in it: as jmosrt253 said, a Humvee engine is a large diesel engine - which means its torque is low down in the revs range Humvee engines, like many large diesels, are not highly tuned. They are built to be robust and survive in extreme conditions up to a point, horsepower is irrelevant for speeds. It is relevant ...


5

Yes, gear ratios are the second largest influence on your fuel consumption. Number one being maladjusted timing. I always relay the story of my and my wife's cars: she has a 1.4 Opel Corsa and I have a 2.0 Turbo Coupe. While my car has more than twice the power of hers and weighs 350kg more, we get about the same consumption figures (she gets 12.5km/l and I ...


4

Anecdotally, I've seen a number of (and been in one) car(s) that has overheated while idling. Without airflow, you're depending on the fans and thermostat for more than if you were driving. If all's well with the car, you should be perfectly fine idling for some time. However, if the cooling system has an issue, or if the oil pump is getting weak, you may ...


4

I doubt it. The engine simply uses more fuel to maintain the current rotations per minute. However, if you're at idle and you notice your revs dip and then come back up that's an indication that a load was just brought onto the motor (the motor would stall or lug if more fuel wasn't added). I have a ScanGauge II and at proper operating temperature with AC ...


4

It is possible that you have a brake or brakes that are dragging. After a 15 or 20 minute drive stop the car and check for a sticking caliper. Feel each wheel in the area of the lug nuts to see if one feels much warmer than the others. They should all feel warm but about the same temp when comparing both backs and both fronts.


4

I think your example is running pretty good, but may be a tad on the rich side. Nothing much to worry about. If it were running a tad bit leaner, the plug would have more of an tan/ash color to it. When reading the plug, don't pay as much attention to the bit at the top of the threads. This area is prone to have some minor carbon build up no matter how well ...


4

Recommended values give you the handling and tire wear that the manufacturer intends for the vehicle. If you increase above that, the contact patch decreases, giving better gas mileage, but you start sacrificing handling and causing abnormal tire wear.


4

I think you need to do a throttle position sensor recalibration (reset). (NOTE: I will post several different adjustment versions. I believe the top one is what you need (for a K8 engine), but will include another four depending on your engine.) To do this for your vehicle you need to follow the steps below, depending on whether it is a stick/auto and ...


4

I doubt you're going to be able to have someone put a number on this. I'm betting you also know that just because no error was thrown, it doesn't mean that the sensor isn't impacting performance. Lifehacker notes that replacing them could improve mileage "up to 15%." As @BobCross mentioned, "most people wouldn't consider it worth their time to do the ...


4

As @LynnCrumbling stated, this would be hard to put a number on, mainly because it depends on too many factors. This is what I can tell you. When O2 sensors get old, they don't necessarily go bad, what they do is get lazy. When a good O2 sensor is doing its thing, if you were to look at the readings from it, the numbers go all over the place, from top of the ...



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