Civic Si: Your Gas Mileage

[Goo]

Recently drove from Houston to Tucson, with premium gas (don't know if it makes a difference) I got:
36 mpg @ 70 mph (over 400 miles on one tank)
27 mpg @ 80 mph
Car had 3000 at the start and was on cruise most the time.

Frankly I think 36 mpg is awesome for the 'fast' civic, especially when EPA was 29 mpg highway.

[murmur]

Originally Posted by Goo

Recently drove from Houston to Tucson, with premium gas (don't know if it makes a difference) I got:
36 mpg @ 70 mph (over 400 miles on one tank)
27 mpg @ 80 mph
Car had 3000 at the start and was on cruise most the time.

Frankly I think 36 mpg is awesome for the 'fast' civic, especially when EPA was 29 mpg highway.

How'd you DO that? I recently made a round-trip of 630 miles, controlled-access highway all the way, averaged 74.3 mph. Got 31.8 mpg.

(I guess there was a little in-town driving at the destination, in there. 93 octane gas. I have about 7500 miles on the car, now.)

Dave

[2008sedanSi]

Just filled up for the second time, and it is a little better 27.9mpg. I would like to see 30 or better. I kept logs of my EX, and last year in the summer was my worst mpg 32-34, so maybe it is just because it is hot as shit in Florida right now. My winter months were 35-38mpgs in the EX. I am keeping a log for the Si, and I will see if there is a pattern.

[speeder]

Originally Posted by murmur

How'd you DO that? I recently made a round-trip of 630 miles, controlled-access highway all the way, averaged 74.3 mph. Got 31.8 mpg.

(I guess there was a little in-town driving at the destination, in there. 93 octane gas. I have about 7500 miles on the car, now.)

Dave

Sounds like you got exactly the same gas mileage as Goo. He got 36 at 70 and 27 at 80. Therefore, if you took the middle of each you would have 31.5mpg at 75 mph. Prob doesn't work out exactly like that but it would stand to reason that you are right in line with him.

Remember, all the Scan Guagers say there's a sweet spot between 62-67mph. That speed with cruise control is how guys are pulling 40+

[murmur]

Originally Posted by speeder

Sounds like you got exactly the same gas mileage as Goo. He got 36 at 70 and 27 at 80. Therefore, if you took the middle of each you would have 31.5mpg at 75 mph. Prob doesn't work out exactly like that but it would stand to reason that you are right in line with him.

Remember, all the Scan Guagers say there's a sweet spot between 62-67mph. That speed with cruise control is how guys are pulling 40+

Hmmm, you're right! I'll slow down a little next time and see if that helps me out. I guess I was assuming the MPG curve was kind of *flat* around 70 mph, but if it maxes out in the mid 60's, then it makes sense that it would decrease a fair amount from 70 to 74...

[simons2k]

Just recorded 345 miles on my Si's tank of gas (FA5). Vtec'd once :)

This is combined street/highway.

[OrdnanceMarine]

Here's a write up I posted in another place:

Driving south on HWY 99 from Fresno to Bakersfield I decided to get some consistent numbers for a completely flat highway cruise. Speed limit is 70 MPH once you leave Fresno and until you get a few miles north of Bakersfield. Where the highway "dives" below overpasses I used manual throttle inputs to accelerate slightly on the descent and decelerate slightly back to 70 MPH by the top of the ascent, essentially keeping LOD (for those ScanGauge users out there) constant and minimize the effects of these slight terrain changes. Same technique was used for overpasses, which there aren't nearly as many of on this stretch of highway. Tire pressure was 40 PSI @ 90F "cold" since that's what my garage runs right now (roughly equivalent to 38 PSI at 70F). Outside temps were in the high 90's and the A/C was on the entire time.

I reset my trip gauge once I hit the freeway and at the start of each run after stabilizing at a test speed and over the course of 10 miles @ 65 MPH I saw 38.2 MPG. Once the speed limit stepped up to 70 I did too and reset the trip gauge and over 60 miles I saw 36.8 MPG. I then bumped it up to 75 MPH for a little over 10 miles and turned in 33.6 MPG. For S&G's I dropped it back to 65 for 10 miles once the highway had opened back up to 3 lanes and saw 42.5 MPG!?!? No hypermiling besides the constant LOD driving I mentioned earlier, no drafting, etc. I didn't see much in the way of wind (air quality was HORRIBLE last weekend in the Central Valley with wildfire smoke and smog, so winds were light). I'm not quite ready to believe 42.5 MPG on a flat at 65 MPH even though it is in family with the MPG improvement I saw between 70 and 75 MPH. The last 10 miles in to B-Field I bumped it back up to 70 and saw just under 37, same as earlier that drive.

I'm going to need to do some more sampling to validate what 65 MPH yields before I'm willing to stand by that 42.5 MPG number but I do have some ideas why it was higher than when I first got on the freeway.

-When I hit the freeway I'd only been driving the car for a few minutes so while the engine coolant was warmed up perhaps the engine oil wasn't quite there and I'm sure the transmission wouldn't have had time to get all of the way up to temp. The tires wouldn't be quite as hot yet either so their rolling resistance would be a little bit high as well.

-The interior of the car had been heat soaked prior to hitting the road so the A/C compressor would have been loaded heavier than it would be once everything is cooled 10-15 minutes down the road.

I continue to be amazed at how well the Si can do if you want to coax great mileage out of it.

[speeder]

Wow!!! That is amazing! Does mpg seem to be as good at 67 as well? Just trying to figure out if there's anything to this 62-67 sweet spot. I'm just half way thru my third tank of gas on my new/used si. Wanted to get a couple more tanks under my belt before I get the scanguage so i have something to compare with/without cost benefit.

[OrdnanceMarine]

Originally Posted by speeder

Wow!!! That is amazing! Does mpg seem to be as good at 67 as well? Just trying to figure out if there's anything to this 62-67 sweet spot. I'm just half way thru my third tank of gas on my new/used si. Wanted to get a couple more tanks under my belt before I get the scanguage so i have something to compare with/without cost benefit.

I doubt there's much to the "sweet spot" idea, at least with a car like ours that actually has a very flat torque curve, especially in the RPM band we're talking about (2000-3500 RPM). Experience seems to show that once I'm in 6th gear my MPG falls off more quickly with each increase in speed which makes sense since drag will increase four times each time you double speed. A few weeks back I drove a ~10 mile flat stretch of road that has maybe 200' of descent and one overpass at 57 MPH with a neutral coast down to 35 MPH the last two miles as the speed limit fell, windows closed, A/C off and a fully warm car, upper 90's outside, 47.X MPG.

The general rule of thumb is that the lowest speed you can use your lowest gear in will yield you the highest MPG on a flat road that doesn't require you to accelerate.

The ScanGauge will help you with this if you know what to look for. It takes time (and research) to figure out what you need to do to wring out maximum MPG for a given speed. I've been working hard at this in my Si for 5 months and did some work at this for the previous couple of years and I'm STILL finding little things that seem to make a difference in fuel economy.

[Burner]

I'm just curious if anyone posting in this thread has installed an Injen (or any other model) CAI in their car? If so, what (if any) difference in MPG did this make? I would also like to hear from people who have installed an SRI, and what their experiences with gas mileage were. From what I've read, I would expect more of a gain from a CAI, but I could be wrong.

I guess any gain in MPG depends upon possibly wanting to more with the intake installed.

[Bboy_Burst]

Originally Posted by Burner

I'm just curious if anyone posting in this thread has installed an Injen (or any other model) CAI in their car? If so, what (if any) difference in MPG did this make? I would also like to hear from people who have installed an SRI, and what their experiences with gas mileage were. From what I've read, I would expect more of a gain from a CAI, but I could be wrong.

I guess any gain in MPG depends upon possibly wanting to more with the intake installed.

makes no different for me. its the way you drive. just get a scangauge, it helps a lot. before, i only made it to 35-40 mpg. now i can get 50 mpg if i try.

[OrdnanceMarine]

Originally Posted by Bboy_Burst

makes no different for me. its the way you drive. just get a scangauge, it helps a lot. before, i only made it to 35-40 mpg. now i can get 50 mpg if i try.

What kind of hypermiling are you doing to get 50 MPG? I though that I got exceptional FE in my Si (can get low 40's on trips that don't require me to drive faster than 65 MPH) but that's phenomenal!

[Burner]

Originally Posted by Bboy_Burst

makes no different for me. its the way you drive. just get a scangauge, it helps a lot. before, i only made it to 35-40 mpg. now i can get 50 mpg if i try.

That is great mileage, and I do already have a Scan Gauge. I was just wondering if any mods designed to make your engine more efficient, whether it's an Intake or pulleys truly makes a MPG difference.

[Bboy_Burst]

Originally Posted by OrdnanceMarine

What kind of hypermiling are you doing to get 50 MPG? I though that I got exceptional FE in my Si (can get low 40's on trips that don't require me to drive faster than 65 MPH) but that's phenomenal!

well, if you stay at a steady speed, you'll get good mileage, but if you want more, you'll have to coast. every time you coast, ur mpg will go up. for example..... slowly accelerate from 50-55mph to like 72mph and then coast in neutral. i usually leave the engine on, but if i go extreme, i turned the engine off. now, if you're current trip mpg is at let say, 40.0mpg. as you accelerate SLOWLY your mpg will go down, but slowly. now your current trip mpg should now be around 39.7-39.9. once you start and finished coasting, your current trip mpg will go up to like 40.4 - 40.6. and you just keep doing that and your mpg will go up every single time, of course that's if you do it correctly. once you get to the 50mpg range and coast, it will only go up like .1-.3, so 50.1-50.3. the higher your mpg, the harder it is to raise it up, but its not impossible, just gotta try very hard and go extreme. keep in mind, if you accelerate quickly to the destination speed and then coast, its not gonna work because of the extra gas USED to speed up. also, acceleration is what kills mpg, so gotta be gentle on the gas pedal. if i really concentrate, i can do 40mpg acceleration and even 50mpg acceleration in 6th gear. hope this help. best to date mpg is 52 mpg with engine on & 57mpg with engine off. keep in mind, i have a Si, not R18. maybe i should do a video, so everyone can have a better understand.

Originally Posted by Burner

That is great mileage, and I do already have a Scan Gauge. I was just wondering if any mods designed to make your engine more efficient, whether it's an Intake or pulleys truly makes a MPG difference.

I have a CAI on my car. i wanted to get as much cold air as i can to get better mpg, but i haven't notice any difference. if i did get better mpg, it would be like 1-2 mpg better, but i doubt it. i've already order NST Pulleys to see if it makes any difference, but i haven't install it though, don't know how to. i'll give an update on my mpg once i figure out how to install the pulleys.

[OrdnanceMarine]

Originally Posted by Bboy_Burst

well, if you stay at a steady speed, you'll get good mileage, but if you want more, you'll have to coast. every time you coast, ur mpg will go up. for example..... slowly accelerate from 50-55mph to like 72mph and then coast in neutral. i usually leave the engine on, but if i go extreme, i turned the engine off. now, if you're current trip mpg is at let say, 40.0mpg. as you accelerate SLOWLY your mpg will go down, but slowly. now your current trip mpg should now be around 39.7-39.9. once you start and finished coasting, your current trip mpg will go up to like 40.4 - 40.6. and you just keep doing that and your mpg will go up every single time, of course that's if you do it correctly. once you get to the 50mpg range and coast, it will only go up like .1-.3, so 50.1-50.3. the higher your mpg, the harder it is to raise it up, but its not impossible, just gotta try very hard and go extreme. keep in mind, if you accelerate quickly to the destination speed and then coast, its not gonna work because of the extra gas USED to speed up. also, acceleration is what kills mpg, so gotta be gentle on the gas pedal. if i really concentrate, i can do 40mpg acceleration and even 50mpg acceleration in 6th gear. hope this help. best to date mpg is 52 mpg with engine on & 57mpg with engine off. keep in mind, i have a Si, not R18. maybe i should do a video, so everyone can have a better understand.


I have a CAI on my car. i wanted to get as much cold air as i can to get better mpg, but i haven't notice any difference. if i did get better mpg, it would be like 1-2 mpg better, but i doubt it. i've already order NST Pulleys to see if it makes any difference, but i haven't install it though, don't know how to. i'll give an update on my mpg once i figure out how to install the pulleys.

You've probably been asked this before but are you validating your ScanGaugeII calibration with your fill up information? I'm not talking about adjusting your SG2 calibration each fill up, but keeping a log of how much fuel your SG2 "thinks" you burned along with how much it took to fill up the tank and comparing this over a number of tanks. For example, fill #1 SG2 reads 10.5g and pump shuts off at 10.7g, fill #2 11.8 g on the SG2 and 11.7 g at the pump, and so on and so fourth to get a calibration using something on the order of 50 gallons worth of fuel. You might have trouble doing this because the car and therefore the SG2 doesn't know about distance traveled when the ICE is turned off.

[Bboy_Burst]

Originally Posted by OrdnanceMarine

You've probably been asked this before but are you validating your ScanGaugeII calibration with your fill up information? I'm not talking about adjusting your SG2 calibration each fill up, but keeping a log of how much fuel your SG2 "thinks" you burned along with how much it took to fill up the tank and comparing this over a number of tanks. For example, fill #1 SG2 reads 10.5g and pump shuts off at 10.7g, fill #2 11.8 g on the SG2 and 11.7 g at the pump, and so on and so fourth to get a calibration using something on the order of 50 gallons worth of fuel. You might have trouble doing this because the car and therefore the SG2 doesn't know about distance traveled when the ICE is turned off.

i know what you're saying. when the engine is off, there are some readings that scangauge doesn't read. when i turn off my engine, function such as "Current Trip" doesn't read as well as other function don't work. and yes, i do set the scangauge ready for use when i fill up and i do compare scangauge to the amount of fuel i needed to fill up the tank to the first click, sometimes 2 clicks.

if i do EXTREME Hypermile, i get the results at the pump, not from scangauge, therefore scangauge is only there to help maximize my mpg. if i do moderate hypermile, i leave the engine on and base the results from scangauge & pump and from all the comparison i've done, its pretty accurate. my scangauge is calibrated and setup correctly for my car also, so don't worry about that part. i usually make up my mind if i want to turn off my engine or not after i finished pumping because once i turn off my engine and coast, the results will be different in the end.

btw, what is ICE ??

[OrdnanceMarine]

ICE = Internal Combustion Engine, a acronym borrowed from the hybrid folks.

I'm unable to touch your numbers unless I'm driving ~55 MPH or so on flat terrain with the car completely warmed up and get to coast in to town at the end as the speed limit falls to 35. Then I'm forced to drive through town with 9,347 stop signs and lights which doesn't help at all but still yields low 40s.

I'm not a fan of shutting down the ICE for a host of reasons even though the Si is better than most in this respect with EPS as long as the ignition is in the "ON" position. A while back a car full of teenagers killed themselves coming down a local pass where the driver shut down the ICE and clicked the key one stop too far and locked up the steering wheel, ran off the road and they tumbled through the desert to their death. No steering + limited braking + disabled passive restraints = not living to tell about saving .2-.3 GPH (about $1 per hour) in our case.

[speeder]

I've heard that aprox 1% or less of all si's are going to do much better in mpg than the majority - just by random chance. I think its quite possible that Bboy Burst got his hands on one these. What are the chances that one of these anomalies would go to an avid hypermiler

[Bboy_Burst]

oh yea, this goes to all hypermiler..... make sure you know the road the ur driving on. don't turn off ur engine when you know there's a turn coming up cus unless ur engine is on, you lose power steering. i had to learn that the hard way when i first started and almost kill myself; i barely made it through the turn and thats because i was quick enough to get the engine running again. when you turn off your engine, make sure you switch the ignition back to the "ON" position as soon as you can to prevent steering wheel to lock up. like "OrdnanceMarine" said, your life>.1-.5 extra mpg.

[iCeMaN57]

I have had my si for 2 weeks 90% interstate travel and i got 33.4 mpg and thats with a little bit of V-tech'ing.