So I have a trip to take and I have two options for the route and I’m wondering which uses more gas, thereby costing the most.
Route A: 27miles long, lasting approx 43minutes and I would guess an overall average speed of 50mph
Route B: 28miles long, lasting approx 34minutes with an average speed of 70mph
Is one better than the other or are they the same?
Route A average speed = 37.7 mph, Route B average speed = 49.4 mph.
If A is stop and go, and B is non-stop, you’ll probably use less gas with B. And save time.
Also, unless you’re only concerned with short-run costs (“how much money must I have in my billfold”), you need to consider wear and tear. Highway miles are much easier on your car, particularly brakes and suspension.
If you want to save more, try lowering your max cruising speed (NOT average enroute speed, or even average rolling speed) to 60, law and traffic permitting. Knock about 20% off your fuel burn.
Look at it as donut-coffee miles.
Miles per gallon is a measure in miles and gallons. There is NO MENTION OF TIME. Obviously, cars get better gas mileage in general traveling at more moderate speeds which does take a little longer over the same routes. But, you use less gas the entire trip regardless of how much more time it takes. We get this question every once in a while. Just take the same trip at two different speeds over the SAME roads. Then compare the gas used. If you save gas by going faster, you just invented a new way lowering gas usage. No speed limits !
Now, traveling over two different routes introduces additional factors that affect mileage like, different terrain (hills) and more stop and go driving. So, the average speed is deceptive if the terrain or driving conditions are different. Again, just measure the gas used by filling up at the end of each route a and b and use that to determine miles per gallon over the different routes, regardless of your average speed differences. The information given over the two routes is incomplete and determining gas mileage over two differnt routes has NOTHING directly to do with time traveled. It has to do with gas used in the number of miles traveled; hence, miles per gallon. As a general rule, cars tend to be more efficient and use less gas when the driving is easier on them…hence, the route with the higher gas mileage would IMHO, be easier on the car.
Gas used In gallons and miles traveled are all you need to know to figure miles per gallon.
Well, say you went the same speed. You could go 27 miles cheaper (spend less on gasoline) than 28 miles. Right? And if you go faster, you use even more gas/mile. So it seems to me 27 miles at 50 mph would definitely yield the lower gasoline bill.
That would be true, if you were traveling the same routes. But, in this case, not necessarily as these are two differnt routes and even if the average speeds were the same, using cruise ontrol for example, lots of hills in one would dramatically affect mileage. Just divide the miles traveled in route a by the gas used, and do the same for route b. You then get the miles per gallon used by each. If you say, tried to keep your speed within 5 miles of the speed limit for each, it should give you the most economical route. Of course, filling up a car after only driving 28/27 miles has to be done carefully.
@dogosa … true, but to me this looks like one of those trick questions. It is phrased in a way to make you think about time and mph and mpg, when the question is really: Which route will take the least amount of gas? And while it is possible to come up with an exception with steep hills and rutted roads and the like, generally nobody’s going to argue with the idea that a 27 miles route will take less gas to complete than a 28 miles route, and that fact is especially true if you are going faster on the 28 miles route.
B is likely the best route. To save gas, drive at 60 mph instead of 70 mph. B seems to have less stop and go’s and that is what really kills mpg.
My good friends @unleturbo and @GeorgeSanJose. There is no trick to this question. Measure the amount of gas used for each trip !!! That will be the lowest cost . But, mpg is important because it will tell you which trip is the best for the car which imo, is what the debate should be about, and not gas used. You get it all by just filling it up when you finish. If you say “generally no one will argue that a 27 mile trip will take less gas then a 28 mile trip” ? Over different routes, I certainly will and I hope, others will say, you can’t tell.
OP is guessing about actual speeds traveled and only knows average speed and we are entirely guessing about terrain. But, you can find the amount of gas used easily, and that determines the cost…case closed !
@dagosa: the route is 27 miles long. That’s around 1 gallon burn for most cars. Even if one route was 10% more fuel efficient, the 0.1 gallon savings would be buried in the “background noise” of variances in fueling. So “measure fuel burn” is insufficient if we’re assuming OP is going to refill the stock tank at a standard gas station.
@GeorgeSanJose: It isn’t quite as simple as “which uses the least amount of gas.” In the title, at least, OP wants the “cheapest” option. That means factors like how wear intensive the route is, and even the accident exposure risk must be considered. If one route saved 25c in gas, but had several steep, switchback descents over potholed roads, it may well be the more expensive option.
Taking the same route in both directions helps mitigate variances in fueling. If the difference turns out to very little, like you say, you have your answer immediately. It doesn’t mattered much gas wise.Taking the same route over several days does even more to make it valid. If OP is just taking one trip, one time and the distance is only 27/28 miles, who the heck cares in the life of a car ? The question then is insignificant short of driving through a mine field… But, if it’s a daily trip, yes, it makes sense like any longer trip to just measure gas used over the continuous use of one route vs another…and ultimately finding mpg to get a feel for what is easiest on the car over time.
Oh I agree, measure gas used–I just think you’d lose the “signal” in the noise of stuff like differing fuel densities by temperature, differeces in inclination while fueling, flow rate differences if someone else is fueling up, etc.
Measuring small differences with imprecise measuring tools is very difficult. To get a result with an acceptable level of certainty, often one has to repeat the experiment thousands of times to reduce the std. Deviation enough.
Also, “take the same trip over several days” makes the fairly bold assumption that the ONLY thing OP does with the car is go A–> B–>A–>B, etc.
(Seeing as how OP has issues with the concept of “average speed,” though, I think confidence intervals are a bridge too far.)
Our Garmin Nuvi 1450 has three choices when choosing a route; fastest time, shortest distance and best fuel mileage. I have not determined how it works and wonder if a smart phone app. provides these choices.
B but holy cow, I can do that many miles going to the hardware store.
Hmmmm, 1 mile or 9 minutes. I think someone is seriously over-thinking the situation. If your fuel or time budget has that slim of a margin you may need to rethink even owning a car, and not making the trip at all.
It’ll be interesting to hear back from @CThom on this one. It’s a fun thread. I still maintain it is purposely phrased to be confusing, and to elicit back and forth comments. It’s like that drawing which appears to some to be an old woman with a wart on her nose, and to others, a beautiful, young feather-hat wearing dancing girl. It’s a matter of perspective in other words.
Let me phrase the question this way, omit the word “average”: Two routes, same origin, same destination. A is the shorter, 27 miles, and the travel speed is 50 mph. B is the longer, 28 miles, travel speed is 70 mph. Assume each is a flat trip on a smooth paved road with no need to slow down or stop. The speed on both routes is constant for the entire trip in other words. Nothing needs to be measured. Wear and tear on the car and how long the trip takes is irrelevant. Which route would use the most gasoline? The shorter one? Or the longer one?
But, if the two routes are not the same and there are significant hills on the longer route along with much higher speed limts while the other is relatively flat with lower but continuous speed zones, you can use significantly more gas to maintain the higher speed. You can have two totally different outcomes based upon what you assume. Therefore, nothing can be deduced from the info given and all you have left is measuring gas used. As a problem, it only makes sense even considering it if the trip is routinely ( perhaps daily) made.
Does it really matter though for a 28 mile trip?
True @dagosa, the problem as stated is ambiguous cannot be solved except by measurement, exactly as you say. Likewise, comparing 27 to 28 miles, what’s the point of even worrying about it, like @Bing says. But, to me anyway, this sounds more like the makings of a Car Talk Puzzler question, not an actual question the OP needs help with.