Wow, I didn't think this thread would be so active after I started it. I haven't been on this board for a very long time.

Anyway, I do much better now than 52.2 MPG when I started this thread. an "easy" tank for me with my terrain (hills, rediculous amount of reds, etc.). My highest so far, though not very far from the norm, displayed as 57.2 MPG. Following my displayed AVG x12 rule, I filled up at 692.1. However, I filled 11.7 gallons. I hand calculate that to be somewhere around 59 MPG. It takes discipline.

Ultimate, I slow accel through the (now 9 lights, was 7) on my ~3 mile stretch to the freeway from home and glide most of the way. Posted speed is 50, I usually slow accel to 25, medium to 35, and feather touch to 40-45 and glide. That serves me well. I do the same on my way home, but I gain 400ft altitude in that stretch. I accel to about 40 then glide as much as possible. On a fresh odometer reading (where so much as farting effects the displayed MPG's) I'll usually arrive home very close to what I started MPG wise from the bottom of the hill.

Once I hop on the freeway, I have a 31 mile commute with little traffic. I cruise control at 60MPH the whole way, both directions. The cruise control, despite the many hills/slopes/overpasses, will get me 53 or so MPG. When I feather-touch the pedal at ~58-63 MPH, I can do better, I'll usually pull about 55-57 displayed MPG. But when I go SCUBA, I'll lose my MPG's if I'm not careful, because of the city driving and pedestrians all over Laguna Beach. But 52 MPG isn't abnormal under even terrible driving conditions for me these days.

The other thing, my car can sense when I'm tense. So cruise control really keeps me at ease and helps my MPG. I'll just stay out of everyones way as much as possible.

In any case, I'm glad to see others making the 600 mile club. Can't wait until I'm 700 miles.


Thanks,
Shawn

 

Tiger, impressive. But this leads me to an interesting question: does the Civic have 12.3 gallon tank or 13.2? You got 13... but I read the manual, says 12.3. If I get 13 gallon tank, then I'd adjust my AVG MPG x12 rule to AVG MPG x13.

I have '06 Civic Hybrid.


Thanks,
Shawn

 

Shawn - If you refer to my post ("Re: 500+" on 09/01/2006) you will see that I filled up my car with, get this, 14.233 gal !!! If we have ~1.8 gal reserve then that is about 13.4 gal or maybe closer to 13.2 gal. Still, nothing was leaking out so the ultimate that I have seen so far has been 14.25 gal so forget the notion of having a 12-gal tank with an additional 1.8-gal reserve. Feel free to take a 1-gal can with you somewhere and test this for me as not many people have duplicated this feat.

I know we don't have the expandable bladder like the Prius so am unsure where the fuel went if not to the tank (perhaps the overflow tube to the carbon filter?). I assume if I filled the carbon filter thingie with gas that it would not perform as well; however, this tank was 41.5 mpg (should have been about 47 mpg but you can read the post to see why). The tank following that large fill-up was 53.3 mpg then 45.1 mpg then 44.0 mpg, 44.8, 46.3, 48.4, 49.9, 55.0, and 56.7. I didn't see it affect my tank averages over the next 9 tanks (which only took 35 days to cover the 5,158 miles or 573 miles/tank average and 147 miles/day average).

 

I used to fill my tank up to the top of the filler neck. It always took 1.8 gallons after first click. I had no ill-effects from doing this.

I don't do it anymore... I just go to 1 gallon over first click... simply because it takes a while to get the last 0.8 gal pumped in!

 

I fill up to the second click now. I've found that my computer MPG estimations are very close to my calculated (at the pump) actual MPG. When I stopped at first click for a few early tanks, my actual MPG was always 1-2 MPG higher than the car's MPG computer.

 

The fill-up discrepancies create the wide variety of mpg calculations. An extra gallon in the tank would increase range by 50 miles. But if you put in 13 gallons, and only calculated mileage by the 12.3 gallon capacity listed in the owner's manual, you'd get an artificial mpg reading.

The only true way to calculate mileage is by running the tank completely dry, then filling it with a precise quantity of fuel, then running it dry again. Any other method leaves open several variables, and is therefore unreliable.

BTW, the fuel tank capacity in the gas-only Civic is 13.2 gallons, while the capacity of the hybrid Civic is 12.3 gallons. However, in California (and maybe other states), the hybrid's fuel capacity is only 11 gallons. Here's why:

The Civic hybrid uses a plastic fuel tank that's molded to fit tightly among all the mechanical parts under the car. But CA won't allow this tank because it allegedly emits gas fumes through the plastic, so the state makes Honda install a metal tank. That one doesn't fit as well, and consequently has a lower capacity.

This could explain some HCH II owners' dismal fuel economy calculations. If they're calculating based on 12.3 gallons, but only getting 11 gallons per tank, their mileage would look bad.

So check your fuel tanks -- look underneath your car and tap the tank to see whether it's plastic or metal.

 

I got my first 600 miles on my 4th tank at 50.6 mpg. My highest tank was 755 miles at 61 mpg.

 

How true this is can be hashed out between the automotive engineers/mechanics. However, I've read it's bad if you top off your tank. The first reason given was that the fuel in the filler neck does evaporate at a good rate. The second is that fuel can/will flow into the evaporative return (I think that's what it was called) line and backflow into the charcoal canister, thus saturating it and damaging it. If this happens, the car can't (or might not, it's been a while since I read that article) pass an emissions test.

The magazine was Underhood Service, for anyone that's familiar with it. It's a magazine for automotive repair facilities.

 

At first, but the more tanks you run through, the more the oscillations tend to balance themselves out. That's why a sampling is done on a large population of data and not just a single tank.

 

I'm confused... why would tank size have anything to do with MPG? It just impacts range!

When I calculate my mpg, I'm dividing the number of miles I traveled by the gallons I pumped. If I always pump to the same point (in my case, one gallon past first click), then the readings should be accurate.

Granted... if you're talking about just ONE tank, then... yes... you would be inflating or deflating the MPG numbers. That might be why my first tank was so low. I have no clue how much fuel the dealer really put in there. I pumped to the filler neck on the second tank, so I definitely filled with more more fuel than it consumed.

Later on, when I decided to stop pumping to the filler neck (1.8 gal past first click), I purposely backed off slowly so it wouldn't impact my numbers dramatically (next tank 1.6, next tank 1.4 and so on until 1.0 gallons past 1st click... where I've stayed for the past ten tanks (or so!).