What's happening to my MPG? Theories?
#1
What's happening to my MPG? Theories?
Our first tank... I got 250 miles before we hit the 3/4 full mark. This latest tank... I have 140 miles and I'm dipping below the 3/4 full mark.
The first tank we filled up with high octane gasoline. This last tank we filled up with regular... but I was told the Altima hybrid didn't need high octane.
The electronic guage reads 35.5 mpg... which is the same reading it was giving us before when we got 38 mpg off the tank.
Any theories?
The first tank we filled up with high octane gasoline. This last tank we filled up with regular... but I was told the Altima hybrid didn't need high octane.
The electronic guage reads 35.5 mpg... which is the same reading it was giving us before when we got 38 mpg off the tank.
Any theories?
#2
Re: What's happening to my MPG? Theories?
I have a TCH, but I wanted to chime in. I'm always skeptical of any single tank MPG figures, because of the variation of the auto-shutoff on the previous and current fill-ups. (I do NOT advocate continuing to "squeeze" in more gas after the pump clicks off--you'll likely end up forcing some "extra" out the overflow and onto the ground.)
Anyway, back to my theory. Your last 2 tanks were calculated higher than the computer display showed because the pump's auto-shutoff tripped early. You therefore put in less fuel, giving you seemingly higher MPG. Now you're seeing lower MPG because there's no "free lunch". You put in less gas the last fill-up, so now you seem to be going through fuel faster.
I like to average 2 or 3 tanks together to get an idea of my fuel economy. I suggest you make sure your tires are properly inflated and just enjoy driving your new car. Eventually, you'll have enough tanks of gas to give you a more meaningful MPG figure. The best part is that you're beginning at the beginning of the warm weather, when you'll see higher MPG figures as compared to those who bought their hybrids during winter.
Best wishes.
Anyway, back to my theory. Your last 2 tanks were calculated higher than the computer display showed because the pump's auto-shutoff tripped early. You therefore put in less fuel, giving you seemingly higher MPG. Now you're seeing lower MPG because there's no "free lunch". You put in less gas the last fill-up, so now you seem to be going through fuel faster.
I like to average 2 or 3 tanks together to get an idea of my fuel economy. I suggest you make sure your tires are properly inflated and just enjoy driving your new car. Eventually, you'll have enough tanks of gas to give you a more meaningful MPG figure. The best part is that you're beginning at the beginning of the warm weather, when you'll see higher MPG figures as compared to those who bought their hybrids during winter.
Best wishes.
#4
Re: What's happening to my MPG? Theories?
I know you're eager to see how your mileage is--I sure was at the beginning! In any event, resist the urge to keep adding gas after the pump clicks off, unless you're SURE you are well under a "normal" fill-up amount. See http://www.epa.gov/donttopoff/ for more info.
I'm eager to find out how the Altima Hybrid does, mileage-wise, so be sure you post after you have gone through 2 or three tanks.
I'm eager to find out how the Altima Hybrid does, mileage-wise, so be sure you post after you have gone through 2 or three tanks.
#5
Re: What's happening to my MPG? Theories?
B. Goodman, thank you. Our game plan now is to NOT add gas till the yellow light comes on. I think that is supposed to mean we have 3 gallons left and are 17 gallons empty. That will give us a better idea if the gas pump is shutting off too quickly.
#6
Re: What's happening to my MPG? Theories?
Oh oh. Another "Hybrid out of gas" story coming up.
Relax, let the car break in. Note that the engine could be more efficient mileage wise with different gas (it's actually different additive packages, but we call it different gas). My anti-Prius (see below) actually gets better mileage on 92 octane rated fuel (what it is designed for) than lower octane rated fuel. So much so it's actually less expensive using premium.
Relax, let the car break in. Note that the engine could be more efficient mileage wise with different gas (it's actually different additive packages, but we call it different gas). My anti-Prius (see below) actually gets better mileage on 92 octane rated fuel (what it is designed for) than lower octane rated fuel. So much so it's actually less expensive using premium.
#7
Re: What's happening to my MPG? Theories?
The Altima Hybrid has a low compression engine and so is designed for regular fuel. Higher octane will not net it better mileage. In fact it could/should get less mileage. Higher Octane is a slower burning fuel and all of it will not burn during the combustion process. Instead, the excess/unburned fuel is burned within the Cat. Wasted.
#8
Re: What's happening to my MPG? Theories?
I suspect what you say is correct, however, I wasn't advocating using premium fuel in the Altima. I was suggesting -other- fuels may give better mileage, as reported by other hybrid owners (Prius owners mostly). Fuels such as Shell regular.
The bold statement that premium "could/should get less mileage" is a little presumptuous without a test, however, which is why I didn't say it.
The Altima appears to be running on the Atkinson cycle (though this isn't stated by Nissan anywhere I can find). I say this because the engine produces less HP than the tune level in the Altima 2.5s, is reported by Nissan at slightly higher compression (9.6 vs 9.5), but is persumably tuned for better mileage, all indicators of an Atkinson cycle (valve timing shift).
I -would- expect the Hybrid Altima to get about the same mileage as the Hybrid Camry, and so far Marianne is reporting that - about 38 MPG. I'm just surprised it does so without breakin having passed. Perhaps it will exceed the Camry. We can only hope!
The bold statement that premium "could/should get less mileage" is a little presumptuous without a test, however, which is why I didn't say it.
The Altima appears to be running on the Atkinson cycle (though this isn't stated by Nissan anywhere I can find). I say this because the engine produces less HP than the tune level in the Altima 2.5s, is reported by Nissan at slightly higher compression (9.6 vs 9.5), but is persumably tuned for better mileage, all indicators of an Atkinson cycle (valve timing shift).
I -would- expect the Hybrid Altima to get about the same mileage as the Hybrid Camry, and so far Marianne is reporting that - about 38 MPG. I'm just surprised it does so without breakin having passed. Perhaps it will exceed the Camry. We can only hope!
#9
Re: What's happening to my MPG? Theories?
Oh how I wish I drove a couple hundred miles a day so we could get an answer to this sooner... but this is my husband's commuter car... and his commute is 11-12 miles each way... then I use the car for errands as much as possible. We aren't racking up the milleage very quickly.
The little electronic guage continutes to tell us we are doing 35.7-9... which is what gave us the 38 mpg tank... but it was unnerving to see the needle plummet. So far though, the car is registering almost exactly the about of miles per tank on the predictor that we saw before... so hopefully in a couple weeks we'll have an answer.
We've been getting our gas at Chevron because it is on the Tier 1 list, but I will keep my eyes open for nearby Shell stations.
Oddly, our first tank was high octane... and we actually "seemed" to get better MPG... but it is also possible (actually probable) that the dealership topped off as much as possible... and that I got an early shut off on my last tank.
What was odd was that the dealership emphasized to us that the Altima hybrid was designed for high octane gasoline... but the manual obviously says otherwise.
The little electronic guage continutes to tell us we are doing 35.7-9... which is what gave us the 38 mpg tank... but it was unnerving to see the needle plummet. So far though, the car is registering almost exactly the about of miles per tank on the predictor that we saw before... so hopefully in a couple weeks we'll have an answer.
We've been getting our gas at Chevron because it is on the Tier 1 list, but I will keep my eyes open for nearby Shell stations.
Oddly, our first tank was high octane... and we actually "seemed" to get better MPG... but it is also possible (actually probable) that the dealership topped off as much as possible... and that I got an early shut off on my last tank.
What was odd was that the dealership emphasized to us that the Altima hybrid was designed for high octane gasoline... but the manual obviously says otherwise.
#10
Re: What's happening to my MPG? Theories?
Not really. Dealerships across the board have been shown not to be a bastian of hybrid information, especially correct information.
Some amusing stories include an HCH buyer whose salesman couldn't find the plug, a FEH owner who was told that he could run around in EV mode after he ran out of gas (which is true, but you don't want to do that, and you don't get very far.), and so forth. Most owners here had salesman who admitted that said owner was far more informed about the hybrid they were purchasing than the salesman was.
You may also find that the needle to your gas gauge is quirky. It's not uncommon for me to drive 80 miles and be down to a quarter tank according to the needle, yet when I'm to 1/8 of a tank still have 125 miles left to empty on the display.
Last edited by Pravus Prime; 04-25-2007 at 09:55 AM.