bclexus

If you are averaging 26 mph then you have very few stops (stop lights, stop signs, parking, etc.). Also, your average city driving speed while traveling must be moderately high. In other words, if a person traveled at [say] 40 mph it would not take very many stops (stop lights, stop signs, parking, etc.) to drop that 40 mph way down to 15 - 20 mph average.

ECL

You may be correct. And?

DVADER

I'm at 13.6mpg after refill and 11mph average speed.

ECL

And I wonder if that reflects driving style?

DVADER

I def drive like a turtle at times.

ECL

Whatever you say, Darth.

bclexus

It doesn't take many stop lights with a 60 to 140 second cycle length (where the MPG is ZERO while you wait, and practically zero as you brake and accelerate back up to speed) to drop the MPG and average speed drastically. Lets talk about average speed.

I rarely travel very far to a destination when I do city driving because my destination is usually within a 5 miles or less, sometimes far less. I suspect that is common with many people.

For example:
It is very common for me to visit a favorite restaurant about 5 miles from the house. The speed limit is 40 mph on all the city streets, and all the streets have 3 lanes in each direction as well as dedicated turn lanes. There are ten stop lights going to, and returning from, this restaurant. I will usually have to stop at least six times for stop lights going to and again returning from the restaurant, for a total of 12 stops averaging a minimum of 90 seconds each time...and this is not during rush-hour traffic (when during heavy traffic some portions of the trip is creep-along, stop-'n-go between stop lights as I must wait through 2-3 stop light cycles to clear the intersection). From each stop there is an acceleration period where the speed in not 40 mph, and with each stop made there is a coasting/braking period where the speed is less than 40 mph, which I'll say averages around 20 mph.

So, let's put this trip into perspective. Traffic is light. I travel 10 miles. When not braking or accelerating from a stop light I average 40 mph (or .67 miles per minute). I make 12 total stops at stop lights for 90 seconds each for a total of 18 minutes where my speed is zero. Slowing to a stop and accelerating from a stop takes say 7.5 seconds each, or 12 stop lights x 2 = 24 x 7.5 sec. = 180 seconds or 3 minutes averaging half my desired speed, or say 20 mph. Once I get to my destination I will be creeping along slowly in a parking lot looking for a parking spot and going slowly over a couple of speed bumps, and when I leave for the return trip home I will be creeping along as I exit the parking lot for a total time of 1 minute...not to mention the slow speed when leaving from and returning to my residence - backing out of and pulling into my garage. So, lets add all this up and see what we get for a typical trip to a favorite restaurant 5 miles from the house and then back home when the traffic is light and free-slowing.

9 miles @ 40 mph Driving Speed Limit (.67 mi/min) = 13.4 minutes
1 mile @ 20 mph During Accelerating/Braking (.33 mi/min) = 3 minutes
0 miles @ 0 mph Waiting 90 seconds at 12 stop lights = 18 minutes
- miles @ 0 mph Backing/Pulling Into Garage = 0.6 minutes
- miles @ 5 mph Traveling in Parking Lot = 1 minute

10 Total Miles Traveled in 36 Minutes (18 minutes each way) equals 16.67 mph Average Speed

~~~~~~~~~

During rush hour with stop-'n-go traffic between many of the stop light intersections the speed will drop drastically on much of the trip from 40 mph to around 30 mph or less, so I'll drop it a bit to 35 mph. Also, more stop lights must be stopped at due to traffic congestion, with some stop lights having to be stopped at twice before clearing the intersection. Thus:

9 miles @ 35 mph Driving Speed Limit (.58 mi/min) = 15.5 minutes
1 mile @ 20 mph Accelerating/Braking (.33 mi/min) = 3 minutes
0 miles @ 0 mph Waiting 120 seconds at 14 stop lights = 28 minutes
- miles @ 0 mph Backing/Pulling Into Garage = 0.5 minutes
- miles @ 5 mph Traveling in Parking Lot = 1 minute

10 Total Miles Traveled in 48 Minutes (24 minutes each way) equals 12.5 mph Average Speed

~~~~~~~~~~

City driving in residential neighborhoods or in a small or medium size city with far less traffic and stop lights would of course have far less stopping where zero miles are driven while waiting on traffic congestion or stop lights to cycle.

ECL

Fascinating! And what does all that mean? I thought we were discussing gasoline consumption. Aber wer werden sehen.

bclexus

Gasoline consumption is Miles traveled per Gallon. But how long it takes to travel those miles is significant because it helps to tell a more complete story about the trip.

If you travel for 10 minutes at a steady 60 mph you will travel 10 miles and might get [say] 30 MPG. But, if during this same trip you must come to a stop-'n-go creep along for 10 minutes due to an accident, then your 10 mile trip will take 20 minutes and you're average speed will only be 30 mph. While you have traveled the same 10 miles your MPG will not be 30 MPG because you basically sat still for 10 minutes, and nor will your MPG be what it would be if you drove 10 miles at a steady 30 mph.

Your average speed helps to tell a more complete story about the travel period. It's one thing to drive around a residential neighborhood or small town at a steady 30 mph and only rarely stop at a stop sign and never stop at a stop light and get great MPG. It's a whole different thing to drive in a metro area with traffic congestion and stop lights every fraction of a mile. Both are considered city driving, but they are drastically different. And the average driving speed (mph) will bring this to light...and tell a more complete story.

With respect to my exampled trip to the restaurant (a couple posts up) where I have an average speed of only 17 mph when traffic is light I will get around 18 or 19 MPG. And when I can only average a speed of 13 mph due to heavy traffic and more stop-'n-go driving I will be lucky to average 15 MPG for the same trip. My slower average speed helps tell the story...

JDR76

I'm not ready to cede it all to driving style. I got great mileage in my IS, with the same EPA ratings, engine, and transmission as my GS and I drove it in the same way, on the same roads. Because the GS weighs more, I expected a slight hit in mileage, but in getting about 25% less in the GS, which is more than I had expected. Oh well, still love my GS!

ECL

Obviously, gas mileage varies from model to model, but driving style will produce different gas consumption results in comparable situations, city, suburban, highway, etc. Driving style will also change the average speed. Race from traffic light to traffic light, you will sit longer at many lights, lowering your average speed and wasting petrol. YMMV

bclexus

Since last fuel fill-up with data reset:

Distance Traveled: 35 Miles
Average Speed: 14 MPH
Time: 2 Hrs. 30 Mins.
Miles/Gallon: 17.5 MPG
Fuel Consumption: 2 Gallons

'If' I had traveled those 35 miles at a constant 35 MPH (1 Hour) my fuel consumption would probably be cut nearly in half and increased my fuel economy to ~30 MPG.

ARM350F

You guys have some great mileage, my driving is all city and I get around 13.9-14.4 once I managed 20 all in the city but it was too much work to maintain it. An old S55 that I would drive would get max 8 even with light driving.

r4nd0

I get around 17mpg on my 2014 f-sport rwd, with 80% freeway, 20% city/residential. On a flat open highway at a steady pace, with no headwind, I think 26-30mpg would be possible. Likewise, 100% city/residential with lots of stops, starts and short trips is going to be in the 10-12mpg range. All of this is just conservative driving. Mashing the pedal will result in a precipitous drop from those figures.

emtam

2015 RWD F-sport here. I'm getting about 14-15 mpg. 90% city driving (lots of hills and heavy traffic in San Francisco) and 10% highway driving. The part that really kills mpg is being stuck in traffic while going uphill. In those situations, I get about 11 mpg. Good thing gas is cheap (for now).