Very Confused Hypermiler here.
 

today i filled up my tank due to the fact gas hit a all time high of 4.14 a gallon and one station still had it for 3.96/gallon. Keep in mind my driving habits have changed(p&g/coasting, shutting engine off at long stop lights, not driving fast, not using a/c, and the weather is still HOT) and my mpg when down HUGE from 36.8 to 33.3. the only really differience is doing more p&g, and been doing that quiet well coasting for good long distances. I don't know if it's a hick up in the system or what. (oh btw, same gas station and gas type too) so my real question is. What happen????

one thing is that you are only putting a few gallons in at a time. there may come a time when the averaging must come in to play. if you average this tank (the poor one) with the one before it and maybe even the one after it, then you may get a better picture.

another consideration is to use about 10 gallons of gas before you fill up or maybe 3/4 of a tank and not just a small bit. this will also help with averaging

i've thought about driving longer on this tank, but i have a gas gift card and i figured i would fill up before the price sky rocketed. plus i just have a 11.3 gallon tank and i'm not 100% sure driving it down that low before filling up( have a long commute to work) averaging them together = 35.095mpg still hypermiling, just thought it would be around the 36 mpg range still

my commute is relatively short compared to some on here. mapquest said it was 22miles (that is one way) I checked it with google maps and it said 19.8 which was verified by my odometer. with google, you can change your route to reflect the actual way you go and not THEIR shortest route.

I know I may get railed for this one but: I tried the PandG thing and it didn't seem to pay off for me either. many have said that it takes a while to realize the benefits and perfect the technique. it seem to me like it took a lot of work and I didn't see an immediate payback so I stopped doing it.

I have an auto trans and I have concerns about long term affects of the neutral coasting on my trans. I keep flip flopping on this and don't really know where I stand on it as a whole but the default is the lazy man stance where I get in the car, put it in drive, and go.

also can I suggest a few things that helped me out on MPG. maybe a scangauge, a grill block, and perhaps a warm air intake. my car is not the best platform to start with. it has a 2.2 liter 4cyl and on this site that is a pretty big engine (just from a displacement standpoint). the EPA for my car is 25. I think with a few modifications, you should easily be leaps and bounds over me.

as far as the tank size, remember that the more gas you put in, the less of a variance you are going to get when the pump stops. that 2 tenths of a gallon difference when the pump clicks makes a pretty big difference with 3 gallons but only half that difference with 6 or in my case a very slight difference at 14 gallons (I know, by that time you would have been on the side of the road for a while with an empty tank). but you see what I am saying.

it's wierd the p&g with two tanks i got SUPER mpg 37.5 and then 36.8. i can't afford a scangauge at the moment. i'm planning a grill block soon. and the whole cool/warm air intake is a 50/50 in my book. i think it really depends on the engine. i did the k&n air filter inseret and it worked for my car. i was told by my mech. the tercel enigines are super super senisitive to heat. he said that 9 times out of ten if they over heat, the engine is gone for good. he has two tercels, same year has mine in the back of his shop that overheated once and he uses them for parts. (more and more people here are buying tercels and corollas) which is why grill blocking is something i'm not 100% sure on with this car. better to be safe then sorry you know.

I'd have to agree with BEEF. With a short time between fillups it will only take a few tenths to really skew the mpg numbers. Even getting 33mpg on a 10 gallon tank you should be able to get to 275 miles or more before filling up.

I am somewhat of a safety guy myself. regardless of the gains, if your car is only going to last a month by driving it that way, then it isn't worth it.

the scangauge will tell you all the data that you need. I think in real time as well. if your dummy gauge in the dash says you are overheating, it is usually too late. I watch my temps like a hawk especially now that it is summer and temps are rising.

I was actually considering getting a second one and daisy chaning them together so that I can monitor more parameters at one time. the problem with that is another $160 and I don't think it will change my driving habits enough to pay for itself probably ever. the first one will probably take a while to pay for itself to begin with.

it does teach you a lot about how you drive and where you are putting too much throttle into it. I usually hit 4th (OD on my auto) around 40 or so and I try to ease it up from there to stay in that gear. mine has a bad habit of downshifting if I give it too much gas at that low of a speed.

I did the scangauge first then the grill block and then the WAI. my engine compensates for the IAT sensor so I actually see a gain. other engines don't compensate for it or do it in a different way so you are right when you say it is vehicle/engine dependant. what works for me may not work for other.

at 34+ percent over EPA, I am going to keep doing what I am doing.

I often read that OEM temperature gauges don't really provide temperature info, but are just idiot lights with a needle. Why do people say that? What's wrong with how the gauge works? Mine seem to work accurately and quickly.

holycow,

mine reacts unbelievably slow. I will be up to temp (according to the scangauge) and the needle will still be climbing the gauge to 195. my gauge only has 3 numbers 100, 195, and 260. it will be half way betweein 100 and 195 when my scangauge reads 188 which is where my coolant temp ususally sits. also it will go to 195 when my scangauge is still at 188.

also, my fuel gauge is strange too. (old #s but shows the point) I will get 100 miles out of it before it comes down to full, another 100 out of the next qtr tank(3/4 tank by now) another 100 to get to the half tank mark (that is 100 miles per qtr tank) and the last half tank will only get me another 100 miles.

I have gotten to where I don't trust the gauges in my car. your car is an '08 and mine is a '97 so that may not be true in your car but it sure is in mine. also it is domestic and I'm not going to harp on the quality issues there either.

I see. I have not observed those inaccurate behaviors from my temperature gauges on either vehicle. I'll have to compare to OBD readings when I'm equipped for that.

In my 2002 GMC I have observed its reaction to heavy trailer towing, and I think it was accurate.

My '08 is a German car, known for worse quality than domestics. :)

Don't feel singled out about your fuel gauge. That problem is pretty universal, though yours is a little more extreme than others. On both of my vehicles (and on previous vehicles I've had), the half mark generally sits at 30% of actual fuel remaining...

All of the GM cars/trucks I have owned exhibited the same problems with the fuel gauge. My Camaro was really bad. I never let it go below 1/4 because once that needle hit's the 1/4 mark you better be darn close to a gas station! The needly would also stay above full for about 1/3 of a tank. It's never been a serious issue for me because I know that that's just one of the things that GM vehicles do, and I compensate for it.

I have been told that if your temp was to spike really fast that the temp gauge in the dash wouldn't pick it up depending on how fast the spike is. one theory is that is an averaging situation so that the consumers don't freak out because their temps jump around so much. my temps sitting at a stoplight will fluxuate about 15 degrees (according to the scangauge). my situation with the domestics may be more linked to the cavalier. they are known for creaks and noises.

as far as the gas gauge. I was extatic when I first started keeping up with my mileage. I was at half a tank and had 300 miles on the trip odo. I just knew I could get 600 out of that tank. then the needle went down fast. got 400 out of that tank. now I am semi-regularly getting 500 or so out of a tank.

Guys and gals. Overheating will not happen unless you have a cooling system problem. If you completely block the grille your cooling fan will run a lot more but still keep the coolant temp in a safe range. You may see temp rise if you are sitting in traffic. Completely blocking the grille (assuming it eliminates all airlfow through the radiator may actually be counterproductive since your cooling fan will need more power to replace the electrical energy you are using.

An easy test for your radiator, with the engine running at operating temp, touch the top hose with your finger to get an idea of how hot it is, then touch the bottom radiator hose. If the bottom hose is not significantly cooler than the top hose your radiator is not removing the heat. It could be a loose water pump belt, but probably is in the radiator. If your radiator is 10 years old it has some blockage, after than it can get worse depending on age.

Summertime is radiator time with ambient temps contributing to the loss of reserve capacity in the radiator.

I found that most blown head gaskets were due to cooling system problems, that reached the point where the result is a blown head gasket.

If you are going to restrict airflow to your radiator make darn sure you have a good radiator to begin with.

regards
gary

Also when you run the tank to practically zero the temp of the fuel in the tank gets much higher that when the tank is more full. The fuel temp in the tank rises as the heated fuel returns from the engine to the tank (fuel injection with fuel return line to tank). If the vehicle is not moving, which cools the tank, the temp gets a lot higher. I have measured a 15 degree increase in fuel tank temperature over 10 miles of driving, more so at low speeds.

I wouldnt want to swear this will shorten the life of an in tank electric fuel pump, but I would think over a period of time subjecting the pump to much higher temperatures would reduce the normal life expectancy. Cavitation from driving close to completely empty wont hep either.

regards
gary

The shape of the tank will also play a part in why the fuel seems to run out quicker after half a tank. Some tanks taper in on the bottom half of the tank. Some have and indentation for the spare, and some have a hump in the middle to straddle the exhaust pipe and or drive shaft. It causes less volume of fuel in the lower half.
Mine has the hump.