Consistent over 41MPG highway with Civic
 

I have about a 270 mile drive from home to school that I'll probably perform like once a month over the next year (x2 to come back of course). It's for the most part interstate or at least pretty open highway, though I do drive through some smaller cities along the way. On the drive home for Labor Day I calculated over 41MPG, and everyone told me "no that's crazy, the pump stopped too soon, next time it will be much lower," etc. But on the return trip yesterday I even broke 42MPG!

I did a lot of driving with load up the shorter hills, though on the really long ones I had to bite the bullet and use cruise control at like 63-64MPH. On flat areas I used cruise control at 65MPH or if the speed limit was 60 or 55 (it was just around the cities) cruise control at the limit. I did a lot of engine-on coasting, down hills, to decelerate for an exit or a lower speed limit, etc. The only "mod" besides my driving was inflating the tires to like 38PSI, just under sidewall max of 40PSI. AC was on the whole time, but the fan on its lowest setting.

Overall I just wanted to thank you guys, because otherwise I'd just have had the cruise control at 75 the whole time, burning it up going up hills and stuff without thinking about it, and probably getting like 34MPG. You can see about my vehicle in my sig.

Good job! If you slow down to 55 mph max, I'd bet you would crack 45 mpg. It's tough to only drive 55, but worth it in the end. It might take you an extra 1/2 hour to get there, but a great opportunity to test some slower highway speeds and do some P&G.

Very nice. Keep it up. As you refine your technique you'll only get better mileage.

Hey guys, thanks for the encouragement. When I drive home from school, I usually have my (impatient) brother aboard about two thirds of the journey, and 65 if pretty much the slowest I can go. But I think I will try going 55 during the 90 miles in between his school and mine next time and see if that makes a difference.

:thumbup: Pretty hefty gain right there!

I dunno if it would be better to have this in a different thread, but I have a question about going 55. There are some places where there are some pretty large hills (nothing crazy steep but there are some pretty steep hills, like on the other side I accelerate from 60 to 75 in neutral). I'd probably have to downshift into 4th, right? How should I negotiate these hills with lower speed to be most efficient? Some of them are so long that DWL wouldn't really work, as the slowdown would have to be very subtle to go from say 55 to 50 across the whole entire long hill...you know?

If you find yourself accelerating to a speed that is too high on the down side of a hill I would first try to crest the hill at a lower speed (using less energy to get up and saving gas). If this is not possible, I would then put the car in gear to reduce or hold at or under your max speed. The reason I would recommend this is because while you are coasting in gear, you are using no fuel.

Does that answer your questions? I didn't quite understand your last part about DWL.

Well I was really asking more about going UP the hill, not down it. Going 55 to 50 up some of these hills would probably make me downshift to 4th...I was wondering how exactly to negotiate that. Like should I stay in 5th for a while as I slow down from 55 to 50 then downshift and hold speed (no way I'll be under 50 going up these hills)? Should I just get into 4th at the start of the hill? I know the best thing to do will be experiment, so I'll figure it out, but just any spare wisdom anyone has....

As for coasting down hills, there are no hills that I go excessively fast on (not more than 5 over the speed limit) coasting in neutral. Wouldn't it be better to let myself get going faster downhill and use that momentum to stay in neutral up the hill for a little bit until I'm getting under 60 and then get back into gear? I know that is true at lower speeds, but at high speeds does the drag make so much difference I'd be better off engine breaking in 5th (so using zero fuel but speeding up less)?

You can try cruising up the hill staying close to 55mph. For my accord, a big hill is usually 20-25 on the TPS reading on my scangauge. Your "big hills" may be steeper though. My Accord is an auto and doesn't downshift until the load goes above 90% as long as I'm not losing speed. So, I'd think 5th gear would be doable up a long hill.

It's gonna feel different than normal though. You'll be trying to hold speed, and not have much ability to accelerate. I can regularly break 45mpg in my Accord, so I'm sure you can whip that!!

according to my sg i can get better or the same fe at wot int 5th as i can with1/2-1/4 throttle in 4th. i would say stay in higher gear till u cant take it any longer

I agree with the concept of stay in higher gear as long as possible.

However, the sg is estimating FE based on the airflow and it's perceived fuel flow. But, at WOT, the engine enters open loop mode where the ECU is no longer regulating the mixture (same as when you first crank up).

My Sg appears to be inaccurate while I'm in open loop mode. It will consistently claim that I'm getting 45mpg at 19TPS until it switches to closed loop, at which point it reads 30mpg.

The point of this is:
In spite of the Sg's possible inaccuracy at WOT, IT IS STILL BEST to stay in 5th gear.

BTW Taco is doing a great job at 66% over EPA!!

Congrats to the OP. I've got an 06 civic and my best tank so far as been 43 mpg with only driving techniques. I plan on adding a grill block this fall and possibly some rear wheel well covers. Get us updated on your progress!

I just drove home and got about 40.6 miles per gallon. 30 miles of it was city driving in a small town with lots of stop signs, but I don't think I would have gotten much worse than 30mpg there, and even if you do a weighted average the highway mpg would be like 42.5mpg. A little disappointing.

I drove about 55MPH the whole time. Actually, it was getting late towards then end, so I had a couple of times when I would accidently go too fast (nothing crazy, but once I caught myself at 63 and accelerating up a hill, and once I found myself at 67 on a level area, when I was getting really close to home). There were some times when I didn't know if I should downshift or not...it seemed like the gas gauge was falling rather quickly when I would go uphill and slow to 53-51MPH still in fifth. I started downshifting on the hills halfway through the trip. Here's a place when an OBDuino would be useful.

I think I'm going to drive 55MPH again on the way back. I'll have my tires properly inflated (they're like 36PSI right now, which is okay, but I'd like to be at the sidewall max). I'll try to figure out when I should be shifting and when I shouldn't be. I'll try to read more about VTEC-i and the "fuel efficiency cams" my engine has that I don't understand. I'm driving back on Sunday. I'd appreciate any advise.

LoL!

I've actually had ppl call me a liar - on Honda web sites, no less!

Who the heck would lie about gas mileage?!?!?

Sounds like we get about the same mileage, but 36 psi is a 'flat tire' in my book!

Forget the "sidewall max" and pump your tires up to 50 psi.

It'll be a whole new experience... believe me! :D

Well up to sidewall now anyway. I noticed driving around town it coasts a lot easier, which is great. I've driven about 30 miles in town, and the gas gauge hasn't moved yet....

Now you're getting it!

50 psi, dude... NOT 44 or 66... 50 psi!

It's THE magic number. ;)

I think that the pump last time overfilled a little, or filled more than the other pumps I have used. The fill-to-click long-division method gives 47.8MPG! This was with 65 miles of city driving and then about 250 miles of highway driving. If you do a weighted average with the 65 city miles at 35MPG, the highway is over 50...but I am skeptical. Either way, I am pretty sure this trip was over 45MPG, which is totally awesome. I attribute it to the upped tire pressure and more experience driving slowly. Thanks for the help everyone! Any more ideas would be awesome!

I think I'm going to build an OBDuino too, and that will make it even better.

I've thought about this a lot, and I agree! There is no control procedure, so called!

The bugaboo with all this (fill n' calculate your mileage stuff) seems to be the 'fill-to-click' procedure you use!

For instance, the angle and attitude of the car during filling can make a difference, as to how much gas you can get into it - is it facing uphill or downhill - to the left or to the right? Did you fill the tank fast or slow - and how fast or how slow did you fill it, and does ANY of this make ANY difference, blah, blah, blah...

Really, the only true measure of mileage can be averaging the results over a period of time and space - but - over how many miles do you average it - and for what length of time?

LoL!

I'm a skeptic too...

Sometimes I think we're all making a big deal over nothing - to make ourselves *feel* better about being skeptics - but I'm skeptical about that too! :cool:

I haven't modded my truck at all except to bump up the tire pressure, and like you the results really were surprising.

College student? If you're anything like I was, the car is a locker on wheels. How much junk is riding around in your hoopy that you could remove and not have to take for a non-profit tour of the city? Every pound you save is a pound you don't have to pay to drag around.

I keep it pretty empty. Extra things I lug around are a car cover and a toolbox. On this trip up it was really full though because the guys I took up had tons of stuff. Counting people I might put it over 600 pounds of stuff.