EOC??? Hurting or helping???

[ben98gs]

Did not know if this should go here or "Experiments" so figured I would start it here.

Last tank of gas, I used EOC (Engine Off Coasting) quite a bit. There are 2 "large" hills for the area that I have to go down/up on my way to work each day. EOC is better going TO work then from, the reason I say this is because there is a stop light at the bottom of both before you go back up. My trip to work is ~8 miles at 35-40 mph speed limits. Takes me usually about 15-20 minutes to get to work.

First hill (if on the way to work) I EOC for maybe about .3-.4 miles total (hille is probably .15-.20 miles and then there is a flat area that is maybe .15-.20 miles that you can still coast before hitting the light) and usually get stopped in the line at the light (you cannot see the light coming down the hill as it is past a curve) and I leave the car off until traffic starts to move. This is a pretty busy intersection so it is virtually impossible to hit it just right (maybe 1 out of 5 times, I can put it in gear to start the car and keep going). On the way home from work EOC is less. I usually start before the hill and maybe EOC .10-.15 miles before I get usually get stopped in the middle of the hill (stop light is RIGHT at the bottom of this side of the "valley").

Second hill (if on the way to work) I EOC for maybe about .25-.30 miles down the hill and the flat area at the bottom to the light. This light is not a busy intersection and probably 3 out of 4 times I can put the car back into 4th and keep going. On the way home EOC is less again, because like the first hill the light is at the VERY bottom of the hill around a blind corner, so you cannot just coast down it or you might be slamming on your brakes to avoid a car at the bottom, or to stop for the red light you cannot see until the last minute.

Now, here is why I explained everything. First tank of gas, I did not implore any "hypermiling" techniques IMO. I would put it in neutral and coast to stops, but that is pretty normal for me. I got 38.8 mpg. My other tanks I started to possibly do things (like EOC) here or there, but also had snow storms to deal with so hard to say what might have worked and gotten canceled out by sitting and idling during a traffic jam on my way home from work, but only a slight decrease in MPG. This last tank though I was hoping to possibly hit 40mpg as an average for my daily commute (basically city driving) since I did "hypermile" and EOC and everything I could think to do to get a good MPG number. But upon fill-up I got 34.0 mpg. Which although not "bad" in the grand scheme, not even close to what I expected.

So what do you think might have happened? Is EOC possibly hurting me somehow? I would only think it could help, but with as much as I EOC'd last tank I would have at least expected my MPG to remain the same, not drop. I also inflated the tires higher (were at about 25psi and I bumped them to 42psi and DEFINITELY noticed less speed loss/longer coasting as a result) and I also changed the oil with a synthetic blend (not full synthetic, I bought the blend since it was on sale) with ~5,000 miles on the old oil right before this tank of gas.

Temperature has really remained about the same the whole time (bought the car in Jan/middle of winter) and if anything it has gotten slightly warmer.

Thoughts?


CLIFF NOTES (since I wrote more than I thought I would): Used EOC a lot last tank with no snow storms/long idling like on previous tanks, inflated tires from 25 psi to 42 psi and changed oil, all which I would have thought should have improved my MPG, but it actually decrease. Asking for thoughts as to why?

[theholycow]

Trying too hard can definitely be counterproductive. Try skipping the shorter EOCs, just take the low-hanging fruit (the long EOCs). For the shorter ones, just coast in neutral with the engine on.

Also, remember: The difference between EOC and engine-on neutral coasting is not about distance; it's about time.

[ben98gs]

With the "longest" distance I can EOC maxing out at ~.4 miles (might be a bit shorter than that), should I maybe skip EOC all together? I understand where it would definitely help in the mountians, but I EOC for maybe 20-45 sec. as they are pretty small hills, but then if I do get stopped my engine is already off.

Does starting the car with its own momentum (putting it in gear and releasing the clutch) increase fuel consumption? This is what I was thinking might be hurting me since I really do not have any long distances/times to EOC.

Going to try this tank again with no EOC at all and see what happens. Getting to the end of the snow season so traffic should move pretty smoothly again. Kinda sucks having a pretty good MPG car to begin with, because with only about a 16 mile round trip a day, it takes a while to go through a tank of gas to see how I am doing on my MPG... lol

[theholycow]

I'd guess you should eliminate the EOCs below 30 seconds. Use engine-on neutral coasting instead.

Bump starting may increase fuel consumption with your car. Every car is different. Any starting does use more fuel than a few seconds of idling, but where that balances out I'm not sure.

[DRW]

Have you tried different routes? I agree that a stop at the bottom of a hill will kill FE. EOC might not make any difference if you normally go down the hill with the throttle closed anyway.

[theholycow]

Good point...if you have to stop anyway, might as well DFCO down the hill.

[ben98gs]

Originally Posted by DRW

Have you tried different routes? I agree that a stop at the bottom of a hill will kill FE. EOC might not make any difference if you normally go down the hill with the throttle closed anyway.

There are 2 other routes that (at least according to mapquest) are within 1 minute of the amount of time it should take to get to work as my current route. The problem is that I live ~ at 70th street and need to get to 82nd street. Ultimately I need to head north and west. Next road north that goes across besides what I take (I basically take 79th that turns into 82nd) is all the way up at 96th street, and that is because there is Geist reservoir that you have to cross over and that is the only road that crosses over. You can take 67, but it takes you southwest so you are getting further away.

If you compare my trips (according to Google maps)...

- Right now it is 8.0 miles to work and takes 21 min. If you figure I currently get 36 mpg that means I use ~0.2222 gallons of fuel on my way to work.

- Taking 56th street over to the highway and up to work it is 11.9 miles and takes 22 min. To use the same amount of fuel (~0.2222) and thus cost the same as my current route I would have to get 53.55 mpg.

- Taking Pendleton Pike all the way down to the highway (basically the same as previous route, but continue southwest instead of turning on 56th street) it actually takes less time, 21 min. but it is 13.5 miles. To use the same amount of fuel (~0.2222) and thus cost the same as my current route I would have to get 60.75 mpg.

So as you can see I would have to basically almost double what I currently get mpg to save any money on a different route.

[DRW]

Good analysis. It looks like your routes are fairly short, which reduces overall FE due to more frequent cold starts. Luckily your trip is short enough so fuel costs less than $1 each way.