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47

There is absolutely no reason to use higher-octane fuel unless your car explicitly requires it. The higher the octane, the more compression/heat required to combust the fuel. High-performance engines (turbo-charged, high compression cylinders, etc), a higher octane fuel is needed so the fuel doesn't combust prematurely (knocking). If you put this fuel in ...


41

Both previous posts are pretty good. I'll add a few more considerations though. On a low tank, during hard cornering, some cars will uncover the fuel pump pickup and starve for fuel. There's been some discussion for years now about keeping 1/4 tank as your minimum as the fuel provides cooling for the fuel pump. Some people argue that additional cooling ...


24

There is an unexpected effect to running with a full tank all of the time: fuel is heavy. The actual weight per gallon depends on temperature (and thus on density) but it's on the order of six pounds per gallon (or about .7 kg per liter, if you like doing all your math in base 10...). Obviously, the total weight depends on your vehicle's tank. In my car, ...


22

Use the recommended gas for your car. Going lower than the recommended may reduce fuel economy as the engine may have to retard timing to avoid detonation. Going higher than recommended won't help as your engine is unable to take full advantage of it, as well as the fact that higher octane fuels actually contain slightly less energy (they just offer a more ...


20

I left my Mazda Protege unused in my garage for over a year, and the fuel filter was clogged when I went to start it again. It started fine, but would not rev and was basically undriveable. I'm sure it wasn't great for the fuel injectors, too. Also, I once bought a motorcycle with 10 year old gas in the tank, and the bike wouldn't run at all. I could hear a ...


17

The reason is that motorcycles traditionally have the fuel tank higher than the carburetor, and the fuel feeds with gravity alone. What risks does this introduce that necessitates a manual shutoff? Without the shutoff, if the carburetor float failed to close the valve tightly enough to stop the fuel flow, then gas would continue to trickle into the carb, ...


15

High octane is required for some cars: e.g., a turbocharged car will likely require higher octane to reduce risk of detonation with higher charge temperatures. High octane is also required to get the optimal power out of a tuned car: properly advanced timing will enhance power and economy (obviously, not at the same time). Some cars are capable of ...


14

Knowing that gasoline does not freeze (Ok, it will start freezing at -180 degrees, but this is more than you or your car can tolerate) but that a small amount of water can accumulate in yout tank over time. So, in cold winter weather condition, like here in Canada, if you have a low level in your tank, that accumulated water could freeze and cause some ...


12

Some aspects of this question have been covered previously. In my previous answer, I pointed out that using octane that is too low will lead to retarded timing and higher emissions. With respect to fuel economy, you can never trust someone's casual anecdote about fuel economy. As Mark points out, they're almost certainly going to be operating under a case ...


11

Any oil change place should be able to take it off your hands for a small disposal fee. You can also try calling your local fire department, they may either be able to take it, or they will know of a licensed disposal site in your area.


11

Unless you've got an extraordinary circumstance or legitimate reason for using it, don't. Chances are the usage will temporary make the symptoms subside, only to return again later. The way I see it, if your vehicle required it you would find it listed in the recommended maintenance items list in your owner's manual. I think another side to this question ...


10

Yes, you can buy additives that can be mixed with unleaded fuel. I found a list suitable products on the AA website: Suitable additives There are several proprietary lead-replacement additives available for 'DIY' dosing of unleaded petrol – these will increasingly be found in accessory shops and filling stations. Additives have been in ...


10

So-called "octane number" is a measure of how much the air-fuel mix is resistant to detonation. The higher the "octane number" is the more resistant it is and the more is can be compressed without exploding. The higher the pressure is at the point the air-fuel mix ignites the more efficient the engine works. Modern engines are designed for some rather high ...


10

It's going to be marked as 'E85' on the pump. It's not that common - I've probably seen one gas station in Vegas that sold it, plus up here in Northern NV I know of one or two stations that sell it - and you'll notice that it's cheaper than regular gas usually. Plus the pumps usually carry large warning stickers, too. It's a blend of up to 85% Ethanol with ...


10

The "correct" way to clean fuel injectors is to take them out and use some specialised equipment that also allows you to check the injector's spray pattern and flow, which I doubt Firestone will have - usually only FI specialists do have that sort of kit. My guess is that they were trying to sell you some overpriced additive that you can buy at the store ...


9

As an everyday buyer you won't be interested in the high performance end of diesel or petrol, so here goes: Diesel engines typically rev lower and have more low speed torque - so you are less likely to stall off the line, for example. Petrol engines usually rev higher and get more power at 3-4 thousand revs Diesel seems to be getting more expensive - ...


9

Look up in your owner's manual how capacity your fuel tank has. Next time you fuel up, take note of the difference. In my car it's roughly 2 gallons (7.5 liters). However, realize that modern cars use fuel as a coolant for the fuel pump and running the tank dry often may damage the fuel pump over time.


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

He is mostly right and here's why ... There is an old saying about Harley Davidson Motorcycles. They call them the "Milwaukee Vibrator" because of they way they run. These engines are a 45 deg V-Twin engine (45 degrees is the angle between the two cylinders). In the HD engine, the two connecting rods attached to the pistons share a common journal or "pin" ...


8

There is a trap for lack of a better word to describe in a lot of filler necks to prevent siphoning of the fuel. On the back side of where you put the fuel in you should see two hoses, one large and one small. Take the small hose off at the filler neck and use that as the entry point to put the hose in. The picture below is a typical fuel filler neck, you ...


8

The problem is, the crossfire isn't just high compression, I believe its supercharged as well. Forced induction motors like octane - the high pressure, high compression, and most importantly high combustion temperatures make you more prone to detonation. There are enough electronics in the engine (knock sensor for one) to realize that something is amiss ...


7

It really depends on the storage conditions, but The Straight Dope suggests a storage life of 6 months to a couple of years. The biggest issue to worry about is that the gas degrades and leaves deposits or gums, particularly in sensitive areas like injectors or jets. Another issue is that if accumulation of water in the tank. If the tank is kept full, ...


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

Another difference is that the diesel engines cost more to produce and to maintain. So the diesel version is almost certainly more expensive to buy than the equivalent petrol car, and it usually costs a bit more in servicing. So the rule of the thumb is to buy diesel if you're going to drive more than ~10000km per year or so, depending on fuel costs, taxes ...


7

If you are planning to let your car sit for a while, it also may be adavisable to have a full tank. Less air in the tank means less corrosion of the tank, if you have a metal one.


7

Water in fuel is easy to figure out. Put a sample (say 5 to 10 ounces) of the fuel into a clear glass container. Let it sit. If it separates into two layers, you have water in the fuel. Shown: an obviously contrived example of gasoline (10% ethanol) with approximately 2 ounces of water added - water has visibly sunk to the bottom of the jar.


7

Very untrue. Both car and motorcycle engines are designed for gasoline, and just like cars, using higher-than-specified octane gasoline provides no advantages (unless you're advancing the timing or other modifications, in which case you'll tune for a certain minimum octane). High compression or forced induction designs (turbos and superchargers) in both ...


6

The main benefit is to reduce knocking in higher-compression engines.


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 ...



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