To answer your question in the way that's relavant to my position: Why do I try to fill the tank to maximum capacity?
I think it all started years ago when I was curious as to what kind of gas mileage I was actually getting. I figured the hand calculation out by myself (meaning there was noone for me to ask, and the internet wasn't around). When I figured out how to do it, I wondered how would I know EXACTLY how much was in the tank if I stopped when it clicked. Because the amount of fuel dispensed can vary, probably by more than a gallon in some cases, from pump to pump at the "click," I was not satisfied that the results I would get would be accurate. The variation kills the accuracy of hand calculations.
I experimented with the pumps and found I could fill up to the neck and realized that was the most consitent way to judge the capacity of fuel I used on the previous tank. I continue to calculate mpg this way. ...
FWIW,papa's ody said:It's taken some time reading this thread, however, i'd like to comment on a post some time back.
I too have always been interested in gas mileage, and quickly came to the same conclusion as JyRO about tank to tank fills. And with today's pumps and the Ody's "early" fill, it's even worse. My conclusion is a single tank calculation is quite worthless (unless using JyRO's filling method). There is a way around this however, and it's simply math. Just keep a running average. I've used several methods. One, use 3 (or 5) fillups (sum the gal's and use first and last mile for distance), this will average out the bumps. A computer program or spreadsheet makes this easy, i use a "sliding" mpg calc over 3 or 5 tanks. I also keep a total used average, (total miles driven since i bought the car, divided by total gals) Now that really flattens out the bumps.
I started this back in '91 with my Civic, then graphed the results, and learned something very interesting. the mpg slowly drifted up and down over time, then i noticed that trend was also seasonal. Higher in summer, lower in winter (makes sense really) but quite interesting seeing on a graph. (For what it's worth, i also noticed that not turning on the heat until temp guage came to normal made a big difference -- on the Civic at least)
So, for those that want accurate mpg numbers, but unwilling to follow JyRO's fill plan, just do the math.
I think I may try slowing the flow down towards the end of a tank fillup. As for accurately measuring the fuel economy from tank to tank, I think this is pretty easy if you have some kind of fuel economy display. I would think this would be pretty consistent from tank to tank. The display could essentially be calibrated by using hand calculations over numerous tanks. Anyway, this is what I do.mejmea said:FWIW,
I agree that doing the math certainly is one way of getting overall results that are less affected by individual variation in filling. I think you can get relatively repeatabe results on a tank by tank basis, however, by taking the middle ground between JyRO's method of filling to the brim and the typical method of leaving the nozzle wide open until it shuts off. I have gotten reasonable results by simply going to a low flow (handheld) for the last 2 gallons or so. This creates much less foaming/turbulence as the fuel comes up the filler neck than filling with the nozzle wide open. While it doesn't get as much fuel into the tank as JyRO's, it does add a measure of consistency (some might say insanity! ) beyond what most people do.
I'm definitely joining in the 500 mile club in 4 weeks on a trip. I may even go for 600 in the Odyssey.OdysseyFamily said:Likely the only way I could join the "500 mile club" is by towing the Ody behind a motor home, or something odd like that!
Now my Civic Hybrid... I filled up this am at over 620 miles on the tank and topped off at 11.2 gallons... yes, that's over 55MPG! 12.4 gallon tank, so I am going to try a 700 mile tank at some point!
charlie - I do this as well, but never trust the M.I.D. :stupid: You're right on the money. There's probably some word for exactly what you describe, but in other threads I've said something like this, "the M.I.D. readout may not be 100% accurate, but it is relative ... meaning the error should be fairly consistent."charlie1214 said:As for accurately measuring the fuel economy from tank to tank, I think this is pretty easy if you have some kind of fuel economy display. I would think this would be pretty consistent from tank to tank. The display could essentially be calibrated by using hand calculations over numerous tanks. Anyway, this is what I do.
mark - The only hardpoint here to make a guess from is your low fuel light. Even though I've been able to squeeze 23 gallons into my tank, when the low fuel light comes on, it really doesn't go to much further. So just guessing, I would guess you could've went another 20 to 30 miles. The pucker factor would have been significant.markr33 said:The low fuel warning was on for at least 25 miles. How many miles did I really have left?
I knew I had a few more miles left, but I didn't know where the next gas station was located (sometimes they are far on the turnpike). But really did want to make the 500 - Oh well, I'll try again next summer.JyRO said:mark - The only hardpoint here to make a guess from is your low fuel light. Even though I've been able to squeeze 23 gallons into my tank, when the low fuel light comes on, it really doesn't go to much further. So just guessing, I would guess you could've went another 20 to 30 miles. The pucker factor would have been significant.
Mark - You will not. You will get a lighter wallet though.markr33 said:To see if I get better performance and/or mileage.