Low MPG
 

I've got about 150 miles on the car, been driving mostly under 4k RPM since delivery. I've got about half a tank left and my average mpg is 18.6mpg.

What's up with that? I'm thinking that it should be considerably higher though most of the driving has been city driving.

Between

A) City Driving
B) Who knows what kind of gas the dealer put in?
C) Brand new, tight engine
D) Who knows how long the engine had been run and idling after it was filled and before you got it.
E) Have you spent a lot of time with the car idling while playing with the stereo/nav/other features?

I wouldn't worry about it. In mostly highway driving I've gotten between 28 and 30 mpg with the stick. But at least I know my car has 93 octane in it from the dealer.

Just drive it until you need to refill it. It should get better.

I'm at about 22mpg after a half tank and keeping it under 4k. Change the gauge info screen to the real time mpg setting and watch what happens when you keep your foot on the gas. When I push the pedal to the floor it's around 9 mpg, when I'm coasting on the highway it's around 127 mpg. It's acceleration that uses the most gas, so if you're doing a lot of stop and go city driving and not being conservative with the throttle that's probably what's keeping your mpg down. Conservative driving on the highway looks like it could average high 30's if you're real careful.

Good stuff, thanks for the quick responses.

Car is awesome though, love driving it around. and I upgraded from a '99 Buick!

I've notice the real-time mpg rating jumps all over the place, from what i've read it will get better with more miles.

I'd guess that the dealer was driving it pretty hard or idled it a lot, bringing down your average.

I'd ignore the real time mpg unless you're on the highway holding constant speed, otherwise it's pretty useless.

If you take the car over 2500 rpm econ falls through the floor.

Resetting your avg will help with understanding how to maximize your mpg. Just press and hold the display button when avg mpg is displayed.

Ignore the first tank. Wait until you've put a tank or two of your own through it before you worry.

I'm averaging 25+MPG and rising with mostly city driving so far. My typical shift point is around 4000 rpm for city driving.

I have read Consumer Reports for somtime when it comes to MPG studies and they find that most cars can achieve or beat the highway EPA ratings. City is harder to acheive and beat. Especially if you:
- Have a lot of lights and stop signs
- Take a lot of short trips
- Are driving in cold weather
- Drive aggressive
- Gas quality (high ethanol count) can effect your MPG
- Tire pressure can effect your MPG

Like others have said, your car is not broken in yet so I would not worry. But if you take lots of short trips, or deal with lots of traffic, stop lights, etc you may never hit the EPA city numbers.

No it doesn't. Holding higher rpm than necessary will though.

My first tank was terrible, too. On my second tank, average is around 33mpg. This is mostly highway, with some spirited driving under 4K.

One of the things I suspect is this car due to it's dual power bands is very thirsty in that first band range so it can hit near peak torque at lower rpm. playing with it and trying hard to lift my lead foot a little I can get about a 4mpg swing pretty easily.

I would imagine a solid ecu econ tune to soften that first torque peak for city drivers will save them at the pump. Add in a track day reflash for your driving days to open it up and everyone wins.

When I got my FR-S, the computer said the avg mileage was 17.6 at 7 miles. I went with the dealer when it was filled up at that. At the end of the first tank I was getting 29.3MPG based on calculations, but the onboard computer still hadn't nearly caught up with that.

You may be just suffering from "early mileage lag". Like others have said, I wouldn't worry about it yet. Heck, even doing a rough calculation on what you say above (150miles at half a tank), you are probably getting closer to 30 than 20. Think about it. Based on my experience, when I fill up between 1/4 tank and empty I'm putting in around 10 gallons of fuel.

At half-tank, even if that means you've used 7 gallons would be doing better than 20.

Second tank will show better results. I wouldn't worry about it.

I was surprised to find out how early the car wants to shift when I turned on the up shift light indicator. It wants me in 5th gear at 35 mph lol. Anyway stop driving the car like it's an s2k and let the engine chug a little shift super early.

I got 28-29 mpg on my first tank and that was higher than the stated computer average and a mix of city/highway driving

I think my car was idling quite a bit before I took it off the lot, it said 13.8MPG with around 40 miles by the time it was delivered to me. I thought the mileage was going to be horrible, but by the time I put on 200+ miles it started to get in the mid 20's, and when I filled up at 300 I was getting 31MPG.

I would like to just point out that the tech that PDI'ed my car accidentally filled it with 87. My fuel economy on my first tank was horrible. Now that I've switched to 93, I've been averaging about 26 mpg city and 37 highway.

I averaged 28-29mpg on my first tank with mixed driving... Just filled it up today for the first time so it will be interesting to see what I get now!

I just filled up my tank for the first time on Monday. I did the math from when the dealer topped of the tank. Averaged 23.6mpg on the first fill up. Computer registered 23.5mpg average so it's right in line.

:bonk:
You brought a fun sports car and worry about mpg? Are you serious?

For some of us, this is a fun sports car that is also going to be our daily driver, so yeah, MPG is an important factor. :P

Agreed on the ethanol thing. I lost 3 mpg in my Mini when my local station converted to 10% ethanol. Imagine it would be worse with a higher mix.

I could be wrong but I think the manual says you shouldn't even use 15% ethanol (E15).

It's a 2.0 liter that isn't particularly powerful or torquey so there must be a benefit of mpg. I could understand if he bought a 5.0 liter V8 then your point would make perfect sense.

I agree! I am worried about gas milage. That's part of my reason for buying this car. There is no reason you shouldn't be able to have sports car fun and still get 30 mpg hwy.