T-Knock

Ok, so I get my 2009 Civic Si Sedan in Feb. Ever since then I haven't been able to get past 300 miles on a full tank. I usually fill up on Supreme Techron from Chevron after it hits the last notch on my gauge. It fills up to 11.4 gallons. I almost never redline, and drive mostly freeways at an average of 75mph. I try to maintain between 3.5-4k rpm's. All my other friends with Si's say they can get up to 330 miles on a full tank if they drive conservatively. I don't know what's going on. Anyone have any ideas. I'm down to 10 percent oil at the moment.

Caveman74

I just got 385 out of my tank

ironworker

its really hard to do.You almost have to keep it around 3k on all your shifts and then at best mabey 325,350mabey mabey, thats if you fill up the neck of the gas tank. The most i ever got was around 380 my gf and i went to ohio and back one sat.

T-Knock

385?!?!?!?! That's 100 miles more than what I'm squeezing out. Wtf is going on?

ironworker

I dont know about the other guy but i stuffed my tank full even the neck, and drove with the cruise on the whole way there and back.It was 380 round trip. Iv gotn 325 with 80%hw and 20% city.

hutzman

I drove 330 miles non-stop once and still had about a quarter tank left. They best highway mileage my Si has ever gotten is 35.8 MPG, but usually average 33-34. City is 22-26.

JayJie15

Heard words that there is some break in period before you acheive good mpg? Somewhere around 5k-7k miles on the car. Is this bs or is there some truth to it?

a10thunder

I consistently get 330-340 miles with one tank and I never fill the tank up to the neck. I do mixed city/highway driving and shift between 3k-4k depending on traffic. I get into the VTEC range once in a while, not everyday. The only times I get less than 300 on a tank is when I autocross.

Check your tire pressure and make sure they're not low. I run 36 psi all around just for better everyday gas mileage.

solovus

Your problem is 75mph ... fuel economy for most cars starts decreasing at a rapid rate past 55-60 mph. Your fuel economy would probably improve anywhere from 10-20% if you drove at 55-60 on the highway.

ironworker

This happend to my car after about 10 or 15k i started getting way better mpg's.

BakerIsBored

I also have a 09 si. I'm just not driving mine as hard as you all. I'm getting about 328ish on 11 gal. It all really depends on how you drive, how much you learn to coast, how hard are you coming up to lights, breaking and accelerating. I live in a hill country, so lots of up and down hills. I've learned when to coast, when you start giving it gas, and how to use lower rpm's when I'm on flat ground and just trying to maintain speed rather than trying to remain speedy.

ajpturbopittsburgh

I get 150 to 200 miles on a tank.

madmatt

Got 343 miles last tank when the little orange light finally came on. Worked out to 31 mpg.

This was about 80% highway but with the a/c blasting the whole time. I shift between 3-4k rpm with the occasional run up to redline.

You need to change your oil btw

FijiBlueFG2

I didn't buy an Si for its mpg rating.

I probably get about 220-250 miles per 11 gallons. But I also live in a congested area. When I go out to the boonies, I notice my driving habits are different, I shift much less, and cruise at a much lower rpm.

Having low oil life can contribute to low fuel mileage, as well as tire pressure. Up your tire pressure, and you may get a few more miles.

Also, cruising at 75mph, in 6th gear you will be at or above 4k rpms. From my experience, crusing at anything above 3k will kill your fuel mileage.

pumafeet10

the main thing is how you drive, like has been said before keep it at or below the speed limit, and shift way earlier at ~2-2200 rpm. That is if you want to get good gas mileage.

Andrew Marquis

The biggest determining factor for me and my car is the highway speeds.
At ~75 average I only get about 30.
At ~60 I get about 35 consistantly.

Thats straight highway miles (like on a road trip), but I don't shift at 2k. Thats shifting about 4-5k getting up to speed on the on ramps and such.

Just stay conscious of your throttle load. Keep your foot light!

Caveman74

I filled up this morning @ 11.6 gallons. I had 1 bar left and was at 389.7
Most I have ever got is 406 with zero bars left

FijiBlueFG2

May I ask, how?

When are you shifting?

Do you ever idle your car? Do you drive it cold, or let it warm up? Do you ever shut it off cold?

I probably burn 1/6th a tank just from idling it.

SIVIC 3

i get around 260. *shrugs*

DevilDoc87

damn that sucks.. never tested regular comuting but both ways on a road trip I hit 401 and on way back i hit 378.. the way up there i kept it between 60-75 the way back i was in the 90s lol..

sleeper_civic

I started getting better mileage at 10k and it is very hard to get 300 for me because i do all city driving. Even if for quarter of the tank I do highway then it goes to about 320. If all highway I got a little over 380 with it on cruise doing the speed limit.

i-VTEC_DOHC

i've hit 331 one time.
i've been consistent on 320's every tank
for the past couple months.

K5^

The best I've gotten is 375 mi @ 11.6 gal (70 hwy/30 st). Avg speed: 75-80 mph + a/c.

DBAl

I drive my car with a pretty heavy foot 100% around town and get ~28. I'm curious what sort of mpg I would get on the freeway, but the speed limit is 75 around here, and you tend to get run down if you are doing less than 80 so I can't imagine it will be great.

Caveman74

I usually shift at 4k. Its been warm here, I actually ran the A/C a few times on this last tank.
I always use 6th gear, even going 45. I sit in traffic.. For some reason I have been getting good mileage. I use to only get around 330. I cant wait to see what I will get with the Cobb AP