Dragonus18

I've learned a decent amount about highway MPG but I'm curious about what determines city MPG. Anyone know? Also, before anyone tells me to buy a Honda I'm putting this out there. I'M JUST CURIOUS!!!

HasABetterSN

Amount of cylinders.

Oh and gears. With a steeper gear ratio, in theory you should get better city mpgs, since you have more of a mechanical advantage when coming from a stop, using less gas.

Dragonus18

Are there any other factors?

Dragonus18

Also, if the amount of cylinders is true than how comes Porches get 19 city and their only 4 cylinder?

Harryman2002

How heavy your foot is?

0949er

The answer you are looking for is Acceleration (or more specifically, Rpms). Think about it, on the highway, you are only maintaining a specific speed (for example, 70 mph @ 2k rpms). Your fuel consumption is directly related to your engine RPMS.

In the city your average speed greatly decreases. With "city" driving comes stop and go traffic, street lights, corners, stop signs, speed up, slow down, etc. Each time you stop you have got to go through the gears again to get back up to speed. 1st gear, shift at 3k rpms, 2nd gear, 2.5k rpms, etc etc. Your average RPM would be up, causing you to use more fuel.

Without getting into physics lol it takes more energy to go from 0-45 then it does to cruise at 65-70 mph. I guess this would be a good time to also say that this is one of the reasons why highways have the speeds posted as they do. Turns out that most cars (on average) are most fuel efficient between the speeds of 60-70 mph



Oh, rev-matching and down-shifting also is good at eatin some fuel That awesome backfire sound is just unused (wasted) fuel igniting in your headders

Dragonus18

What about weight? Doesn't that have an effect on city MPG?

TRUEBLUE3934

Yes, weight absolutely has an effect on mpg (highway and city).
If you can avoid coming to complete stops as much as possible, that will help your mpg. If you see a red light ahead, take your foot off the gas and coast or slow down a little. Starting from a complete stop uses A LOT of fuel. If you can smoothly accellerate from 10mph instead of 0mph it will save you gas. Just remember that your brakes are the ANTI-MPG.

If you ever get the chance, drive a vehicle with real time mpg display and experiment with different driving techniques, but mostly watch how much fuel is used when starting out from a dead stop.

0949er

yeah of course weight matters. But then again, it also depends on if you are driving into or away from any wind. Everything comes into play, but the most obvious reason will be rpms.

cliffyk

For any given vehicle it is the weight of your right foot, as mentioned above...