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I currently run a week and fill up because I am not able to make 2 weeks on a tank, just yet.

I remember folks talking about getting better mileage on a full tank. Was that due to carbs- and no longer true due to fuel injection?

Would it be better to run it to E or just as well to fill it between 1/4 and 1/2 as I do now?

I guess the weight involved is 6 or 7 gallons that I always have in the tank.

My guess is that most of us are more motivated when we see the fuel level down a ways on the gauge. It seems to be fairly consistent, though--most people average slightly better fuel economy when they run the tank most of the way out every time.

Also, going from as full as possible to as empty as possible tends to cut down on the relative errors in your fillups, which makes the average MPG slightly more accurate.

-soD

Better fuel mileage with a full tank is very old, and I think it depends on the vehicle.

My Ranger tends to get worse FE when below 1/8 tank, but many people here get better FE when there is less fuel to weigh you down.

I don't know why my Ranger gets worse, I just know that it does.

My guess is that the saying started back with old vehicles and inferior fuel. You would end up with the bottom 1/4 tank or so being mixed with a lot of "gunk" and that would start to clog up your fule filter, not to mention just not burning as well.

It could also be related to weak or worn fuel pumps -- less fuel in the tank could correspond to lower fuel pressure?

It could also be related to weak or worn fuel pumps -- less fuel in the tank could correspond to lower fuel pressure?

That's a good possibility. Especially with my Ranger that has now passed 100K miles on almost all original equiment (one clutch and a set of tires have been replaced beyond normal maintenance).

Low fuel pressure when the tank is low is a known issue on my generation of civic. I deal with it by cycling the ignition a couple times to prime the lines until I can get to a pump. (every time I FAS! :rolleyes:)

Until I get to that point, I've measured improvements as the fuel level drops. I attribute it to the weight loss - about 1% of vehicle weight for a full tank, corresponding to nearly 1% mpg improvement.

THank you all for the answers. I may try to work it down closer to E.

I suppose running on the verge of empty, constantly, would reduce your weight enough to have some impact. My approach: fill till the pump clicks off, and stop. Consume at least 1/2 the tank, more likely 3/4, before refilling.

I'm in the fill weekly (1/2 tank) or at 1/4 tank at the least. It is more of a peace of mind issue with me. Living near Raleigh you never know when there will be an accident, snowstorm or major detour and I would not want to run out of gas.

Hi Ken:

___Go as long as you possibly can before having to pull into the pump as that alone is a waste of your time and your fuel for that activity alone. The TCH is one heck of a car and with a range of almost twice its advertised in the summer, why not ;) Just please attempt to use its own SHM 18/18 on the highway and of course DWL, DWB and P&G with traffic around town.

___Good Luck

___Wayne

I usually will fill up when my gas gauge is pretty low, but only in the summer. I usually fill up around a 1/4 tank now cause its cold out. I have gone about 60km with the gas light on.

What is your commute like?

I drive 40 miles a day (38 highway, 2 city) and can go about 2 to 2 1/2 weeks before filling up in the Winter. 3 to 4 weeks in the Summer. Also depends on how many days a week I volunteer.

Your car is the hybrid so smaller gas tank but my 700 mile tank, I went 100 miles after the low fuel light. Nowadays, I gas up one day after the low fuel light and still get ~14-15 gallons out of the 18.5.

That's a good possibility. Especially with my Ranger that has now passed 100K miles on almost all original equiment (one clutch and a set of tires have been replaced beyond normal maintenance).

Clutch replaced before 100k? How were you driving before? I hope mine doesn't need replacement so soon...

Thanks again all. Good responses and lots to work on. I will check out the SHM watching the timing advance on the SGII. I do alot of P&G and then try to DWL up the front side of these hills. Often I can crest a hill at 55 and set it in neutral and be at 65 by the time I start back up the hill. Then with DWL I can make it about halfway up the next side before I am dropping below 55 and the Semi's are crawling up my tailpipe. So I have to accelerate to the top again and see whats the next hill holds. Since this winter seems much colder than recent previous winters I am thinking my mileage would be more like 42 or 43 during warmer weather. I rarely just drive from point A to point B any longer but I am still nervous about slowing considerably. Warming the engine more quickly has to be a ticket to another Mile per gallon. I am thinking I will get a vinyl bra for the front end and try to block some grill using the bra to help hold in place. I havent found a good posting on the subject for the Camry.

My commute is
Home:
A) 3 miles at 35-40 with 8 lights.
B) 21 miles Interstate Speed Limit 55.
C) 2 miles at 35mph with 3 lights.
Office.
This is reversed in the afternoon for a total of 52miles 5 days per week.
We use the Camry on the weekends, and the mileage varies.

Now the Tank on the Camry is supposed to be 17.1 gal(I think).
I am currently getting 37.8 MPG
leaving 1.1gal as reserve
16 gal x 37.8 MPG = 604.8 miles.
26 miles x10 trips = 260 miles
260 miles x 2weeks =520 miles
That leaves me a little over 2 gallons or one gallon per weekend plus reserve.

So, with my gauge at 1/2 tank and @280 miles driven I will try to make it to next weekend. With less weight for the second week I might see enough improvement to consider just filing the tank 1/2 way all the time. We will see.

Clutch replaced before 100k? How were you driving before? I hope mine doesn't need replacement so soon...

The bad news:
it was replaced at about 35K miles

The good news:
It was pre-hypermiling and I am still running on the replacement.


I'm pretty sure the original had a minor flaw in it that caused an early failure.

If you live in a cold state, I would issue a safety concern about running your tank too low. If anything should happen and you get stuck in the winter, that full tank of gas could be a life saver by keeping you warm. I tend to fill up at around half a tank in the winter. In the summer, sure, let it run down. But it's not worth the risk in the winter.

Good point melinuxfool. Nah its not even considered cool here in most parts of the country. Actually this evening the temp is 55f here in Atlanta, its warming up. However Im not sure if I am going to make a full 2 weeks. The gauge is still at 1/4 tank on level ground. The computer says 70 miles left. Im thinking I can easily make 120 miles to fillup. But, I will probably source a gas can from the mower shed- just in case.

I usually let it get down to about 1-2 gallons left out of my 16-gallon tank before re-fuelling; no reason other than that I don't want to pull into the gas station all the time. Keep in mind though that unlike my car's mechanical pump, your electric fuel pumps rely on having some gasoline around them to aid in cooling, something to think about in the summer. Also, letting the tank get too low leaves you at risk for pulling the trash at the bottom of your tank into your fuel system - more frequent fuel filter replacement alone would kill your cost advantage from not lugging around the weight of a few extra gallons of fuel.

Well I didn't wait but filled up Thursday night. Anyway it was my best tank yet. Albeit a small increase. Almost 40! wohoo!

02/04/2010
39.725 US MPG
531 miles
13.367gal

Hi Ken:

___You are almost there!!! :)

___Good Luck

___Wayne