I issue a challenge!!!
 

Compaq888 is convinced his car gets 40mpg+ on the highway.

I'm skeptical.

According to the EPA a 1999 Nissan Altima will get 25mpg in the city and 30mpg on the highway.

His claim that he has acheived 40mpg on the freeway is based off of two fill-ups, each of which were under 1 gallon.

My challenge to Compaq888:

Drive a total of 200 miles. Drive 100 miles, turn around, and drive back. You are to keep your car in the condition you had it in today when you achieved 36mpg. You said you did this going 65mph using cruise control. You front tires were 37 psi and your rear tires were 35 psi. The same conditions must exist.

Fill up to the first click and no more.

If he achieves 40mpg on this 200 miles trip, I will pay for his gas for this trip. If he doesn't get 40mpg, he pays for the gas himself.

The challenge has been accepted and will commence tonight.

Quote:Fill up to the first
 

I don't want to be a stick in the mud but I have a concern about this fill-up method. I have noticed that if there are other people pumping at the same time the flow rate isn't as fast which means that more fuel could get in before the pump kicks off. I've noticed that when the fuel is flowing fast, it tends to splash more thereby causing the pump to kick off faster. Maybe we need suggestions on the best fill-up method? I'll go first with my method. I fill up at the same pump, facing the same direction, etc. I then fill until the fuel is about ready to run out of the filler neck. Then I shake the car to make sure the air bubbles are out then refill as necessary until the fuel is even with the filler neck. I realize that people who have to use the special pumps that seal up may have a difficult time using this method. I re-filled in St. Louis, MO one time and had to hold the spring loaded seal with my other hand to make the above method work. I agree that a long distance would be the most accurate way to measure fuel economy. The problem is that I don't always have the time to go that far. :-(

I hear your concern Larry.
 

I hear your concern Larry. The thing about always filling up to the first click is that over time it all evens out. The same argument can be used to support the other side. What if on his first fill up he gets more gas than his second fill up? It makes his MPG look bigger than it actually is.

It's things like this that we cannot always control, so I think it's best to not totally worry about them.

Quote:I hear your concern
 

Good point.

And I should also say I
 

And I should also say I don't feel good about releasing the the seal thing because it's there to prevent unhealthy and wasteful fumes from spewing out.

Besides, matt posted something early on in this site's history about the 22 million gallons or something wasted to evaporation.

Hopefully I break 40mpgs
 

Hopefully I break 40mpgs because I think stock intake works better than a WAI setup I got now.

First Click
 

The "first click" system needs at least 2 fill-ups, as I recently found out. The first tank will be highly optomistic because it will use less fuel, whereas the second will be more accurate (which is what happened).

RH77

I do the one click system.
 

I do the one click system. I has some flaws but I agree it evens out in the end.

What a waste of 3 hours and
 

What a waste of 3 hours and 45 min.
Let's not forget the $16.33

I took a wrong route. If I knew the 91 had a 8 mile incline I would not taken it. Also thanks to the construction crews for closing the 91 at the 60 freeway merger and the 605. I took 2 stupid detours.

To add insult to injury the mpg was 31.41
It wasn't the detours and the inclines, or the slipping transmission, it's the car. It's a POS.
I'm never doing a run like this. First moment I'll get this car will be sold. I'll get a manual, so I don't have to wait 5 miles till overdrive works, and get to select the gears myself.

What a horrible night. I should of just crashed it into the construction trucks when I was driving by. At least I would of been given a check for $5000 from insurance and buy a better car.

Bummer, I'll give it a shot
 

Bummer -- I was hoping this would work out. My goal is to get 40 combined in the Integra (80% highway). I've added the EPA estimates, to my signature for good measure. I bet I can get close to 40mpg, right now, at 55 mph for 200 miles. The EPA original estimate for '98 was 24/31. Kansas City has an interstate loop -- I-435 that I could set the cruise for around 58 (55 actual) and loop around town 3 or 4 times to get 200 miles. I'm willing to take the challenge: providing, I can warm up the car first - also no need to pay for the tank or anything, just science in-action is good enough for me. I may have time on Saturday or Sunday to do it (weather permitting -- snow is expected, which kills my mileage).

RH77

I may do the same thing this
 

I may do the same thing this weekend if I have the time. If I only had cruise control.

just switch to EX harneses.
 

just switch to EX harneses. thats got MPFI and cruse allreadt in the harness.

re: cruise - i think i read
 

re: cruise - i think i read before that you've already got the parts from another vehicle, right matt?

otherwise... i got a used aftermarket unit off eBay for my car for $106 CDN - including shipping & currency exchange.

it wasn't difficult to install, but took an afternoon to do it (most of the time was spent planning where it would mount & how to connect to the throttle or throttle cam). i ended up setting it up to pull on the throttle pedal arm since the cam on the TB on this motor was too tiny.

i even moved it all over from firefly #1 to firefly #2 when i got the black car. the second installation didn't take much time at all!

yes, I already have the
 

yes, I already have the cruise control stuff out of another car. The 88-89 civics didn't have cruise control, but the 90-91 civics did. Aside from a few superficial changes the 88-89 and the 90-91 are the exact same cars. As a result I can retrofit the 90-91 cruise control to fit into my 89 civic.

This requires replacing the steering wheel, the pedal assembly, and adding a control box, a "on/off" button, as well as an actuator. It also requires splicing some wires into the dash wiring harness. Overall, however, it will look completely OEM.

I have a rather big car
 

I have a rather big car weighing 1360 kilograms with a 2.0 engine and automatic trasmission.
So far the best MPG in this car is 5.3 Liter/100 km which is approximately 44 MPG.

It was 1.5 years ago at a summer night a 570km (356 miles) trip.. There was only me in the car and according to trip computer my average speed was 78 km/h (48mph). There was no traffic at all and i was driving below 90km/h (56mph) in order not to get a speeding ticket. I drove from cities from Ankara to Afyon and returned back. This road is the few most even roads in Turkey as there is no steep uphills and downhills.

But that was before i was aware of the gas saving issue.. and at that time cruise control was not installed in my car... If i would do the same trip again i think my MPG would be 50 or more..
First of all i would inflate my tyres to minimum 40 psi and use cruise control at cruising speeds of between 60 - 70 km/h (37-43mph), and use the oxygen sensor circuit to decrease the consumption at level roads and downhills. Oxygen sensor circuit dramatically reduces the consumption at part loads. But i dont have an idea whether its related with the onboard hydrogen generator installed in my car.

I did it -- 40 mpg highway!
 

Well, the challenge commenced today.

I needed to drive 250 miles each way to a class (by the way, it's for the SCCA National Rally Championship Circuit, which is coming to Missouri for the first time -- I'll be working medical crew on each stage. The OLN channel carries the Rally, which I think is currently in Michigan "Sno-Drift") I'm excited -- the Rally is on Feb 24-25.

Anyways, getting there was rather inefficient -- it took 10.437 gallons to go 286 miles (27.40 mpg). Speeds were 60-70, heavy rain, and lots of pooling water on the roadway. But get this, on the way home, I decided to set the cruise for 57 mph.

Driving on a Midwestern Interstate at 57 mph when the limit is 70 is not for the faint of heart. I got honked at once, plenty of dirty looks and lots of cutting-off. The goal was to see what kind of true highway mileage this car was capable of. Much to my surprise, the gas guage slowly dropped as the miles went by. Half-way through the tank, according to the guage, I was at 227 miles. Filling up at my usual pump, 4.748 gallons = 47.81 mpg! BUT, there's one problem. The first click-off didn't completely fill the tank.

The gas station 250 miles away from home filled the tank to the F-Mark on the guage at the first click, but Pump #20 at my local QuikTrip leaves it slightly off of the F-Mark at the first click. So, since the tank holds 12 gallons, and the guage read exactly half, I estimate that 1-gallon should be added for a closer-to-true measurement. 227 miles per 5.748 gallons is 39.49 mpg, which is close enough to 40 for me.

Of course, it will have to be repeated for confirmation, but I've come to the following conclusions:

My max highway mileage is at least 40 mpg at 55-60 mph.
Wind resistance really has an effect on my mileage -- driving over 60 really takes more fuel -- I should focus on making the vehicle more aerodynamic.

RH77

I would of probably achieved
 

I would of probably achieved high 30's or low 40's if I drove during the day and not up the mountains.

I'll do the challange again but I'll change a couple of things. Most likely is pumping the tires up to 40 psi and driving 55-60. Plus I need to change the air filter.

xB odometer error
 

Ok here's a good reason that the ScanGauge is reading so high on my MPG and it doesn't come close to the odometer . . . the odometer is off and reads less that actually traveled. I just ran down the street 2 miles measured by my bike and scooters that have rotation calibrated digital odometers with 2 decimal places on the miles and the xB reads 2.0 miles on the ScanGauge at the 2 mile mark but the odometer reads 1.8 miles or about a 10% error. So the half tank mark on the gas gauge that I reached today on the odometer reads 247.1 miles figuring 6 gallons from a prior fillup when at half a tank indicating 41.18333333mpg but the ScanGauge is reading 253 miles 42.166mpg and the gas used at 5.6 gallons and 45.1mpg for the tank some of the error being the amount of gas used is more than the ScanGauge is measuring but not by much.

rh77 -
 

rh77 -

(and everyone else) - why not fill the tank more precisely than "first click"? i used to do first click, but (as you just confirmed), it's not consistent.

a far more consistent method is to actually fill the tank right up the filler neck until you actually see the fuel level at the little metal flap in the pump "hole".

the potential downsides to this are:

- in hot ambient temps you could theoretically have fuel spill out under pressure as it expanded (assuming you didn't drive the vehicle after filling up) - this hasn not happened to me.

- occasionally, you'll overfill, and a bit of gas will run down the paint & evaporate away.

- it takes longer - i'd say i go through 4 or 5 clicks before the level reaches the top of the filler neck to the little flap.

even this method is not 100% consistent (air pockets can be trapped in the tank depending on the angle of the vehicle when filling), BUT it's far more reliable than the "first click" method.

Re: xB odometer error
 

just fyi, JanGeo, my scangauge was 1% off on distance on my last fill-up (over 450 km). its mpg calcs are between 2-3% off (better than) my back-of-the-gas-receipt calculations. but this is within the margin of error since i buy volume-corrected fuel, and the volume on the receipt is not actually what i'm putting in the tank. (a whole other story).

i have yet to calibrate the car's odo, however. i have it on my list of things to do...

When I get a free day you
 

When I get a free day you can guess what I'm going to do with it. A trip to DC would be nice anyway. I'm hoping for 50 highway in my beast.

Quote:a far more consistent
 

This is how I've filled up for years. It's almost an art to keep from spilling it on the paint though. I can usually, by shaking the car, get 1.5-2 gallons more into the tank after the first "click." I also try to eliminate as many variables as possible by using the same pump and pulling up to it in the same direction all of the time. Many people have said that this can cause the charcoal canister to get saturated but I've never seen a problem with that.

Re: Quote:a far more consistent
 

interesting - learn something new every day...

did some searching: overfilling the tank may put raw fuel into the tank vent line (on some cars the vent line connects to the top of the tank; on others it's at the top of the filler neck). if the vent system is filled with enough liquid fuel to saturate the charcoal canister effectively "blocking" the vent function, ODB2 cars will throw a code for Evaporative Emission Control System Malfunction.

neato. i've been filling my tank this way for 10,000 km on firefly#1 and firefly#2, and haven't seen any codes.

Re: I would of probably achieved
 

Doubt it. Driving at night may have had some effect on your ambient air, but your warm air intake might have made up for the difference.

You also cannot blame the mountains for your mileage. You calculated your mileage going up and down the mountains. While your gas mileage may have been worse going up, I'm certain that your gas mileage going downhill was ridiculously high. I have gotten 46mpg going from Salt Lake to Southern California before, b/c the trip is almost a constant downhill trip.

If you want the best mileage, only travel downhill. :)

xB odometer error
 

Nice to know that he ScanGauge is that close and I think it actually is because I went out for a longer ride today and found the gas needle still on the half tank mark for a few more miles like 250miles WOO WOO that puts me over 40mpg for sure and the engine is still breaking in as I drove today the mpg reading kept going up. I have 45.4 MPG average for this "half" tank of gas so far according to the ScanGauge. The speedometer speed on the ScanGauge was 2% low according to my GPS ant that I have adjusted so it may be a little on the higher side of the actual error of 1.5% - maybe I need to let some air out of my tires! Guys you do all realize how big a xB is right and to get this mileage is amazing as far as I am concerned. The best I have heard an xB getting is 39mpg.

I don't think there is any way to adjust the calibration on the odometer in the car unless there is some programming that can be done. What happens to the odometer if you coast with the engine off?? hummmm.

As far as fillups YES the gas charcoal filter can be damages if the tank is over filled - they say this in my Geo Manual 1994 but just drive after filling and you should be ok. Hot days are the killer when that 10 gallons + wants to expand it WILL! Definately keep clicking - the xB has the filler hose enter the tank about 1/3 the way down from the top so a big air pocket is there and I clicked for a couple of minutes. You should also really slow down the fill rate at the end to as slow as the pump can go to allow the air to come out up the filler hose from the tank. The Geo wuld be filled up to the tippity top and spill gas when I screwed the cap in ARG!!! A little side to side would release some air but it like being filled up hill. The xB should be filled down hill for sure - need to find an unlevel station.

Quote:I don't think there is
 

I wish it were as easy to re-calibrate the car's odometer as it is the Scanguage.:-( When I coast with the engine off I have to turn the ignition back on once the engine stops so it will register mileage.

Humm
 

Sounds like it is controlled by the onboard computer but I would really like to have the odometer powered up by a button to I can read the mileage without having the engine running - kills (lowers) the MPG reading sitting idle after a trip . . . it does seem to like starting easier next time however. Just called brother again, there is a sensor usually on the tranny near the axle going to the left front wheel that runs the odometer and speedo and he thinks it is controlled by the computer. May be the odometer reading is a little low to compensate for tire wear and will be more accurate when the tires gets smaller and spins more per mile.

Re: I would of probably achieved
 

You are forgetting that going down a mountain in an automatic makes the rpm go up under cruise control, which uses more fuel. Also the mountain has to be really downhill for the car to keep the same speed while not using the overdrive. Even if I let go off the gas while driving down a mountain the car still slows down. It's complicated but it's a lose-lose situation going down a mountain in an automatic.

I will find a way to surpass 40mpg on long trips. My tires are at 40psi and I plan to do the underbody really soon.

Re: I would of probably achieved
 

I'm not sure I believe that. When I go down teh mountain in my manual in gear the RPMs are REALLY high. That's what engine braking does. The down side of an automatic is that the engine braking is always engaged when going downhill.

Odds are the engineers at Nissan anticipated this and made the injectors fire less frequently while going downhill.

I'm willing to bet that if you put a scangauge on your car and drove downhill your mileage would improve more than you realize.

Gas used is mainly factored
 

Gas used is mainly factored between rpm and load. Higher rpm but much lower load = less gas used.

Re: I would of probably achieved
 

The rpms do go down but the car slows down too fast. I have to speed up a lot.

If the throttle is closed
 

If the throttle is closed and the engine speed is above a set limit, such as 1200rpm in the case of Hondas, the injectors are disabled. That's how engine braking works. Auto or manual trans will generaly slow the car an equal amount, it really has nothing to do with it.

simple solution
 

Well you have to keep the engine turning and in gear to regulate speed unless you want to pop it into neutral so the next thing is to turn off the fuel pump so the injectors will not be operating. The ScanGauge will probably register the injectors opening even with no fuel or you could end up with an engine check light for no fuel pressure. From what I am seening my xB shuts off the fuel to the injectors until about 1000rpm when slowing in 5th gear - it really slows you down then starts bucking below 20mph even with your foot off the gas. ScanGauge shows like 80-120-150+ mpg depending upon speed when slowing down but it senses a reducing speed so if you can put the clutch in or get it in neutral and keep from slowing down then the indicated mpg goes up more. If you have to burn a little gas it still gives you some pretty high MPG. Air density really affects air drag so colder air slows you down more - made a trip in near zero to below zero weather one time in the Geo and couldn't get over 65mph except on down hills from a combination of too cold air into the engine and more density causing air drag. A lot of this shows up on my electric scooter with the amp meter showing drag in hot and cold weather and really affects range. Funny driving the xB feels like the scooter trying to stretch the range by slowing for stops way ahead of time and really light on the throttle.