2008 Altima 2.5 BAD, TERRIBLE, AWEFUL Gas Mileage!?!?!

[sexybeasty]

My 2008 2.5SL Sedan gets terrible mileage. This is not good news for me, b/c i bought the 4cyl for the very reason of getting better mileage than the 6 cyl. I get a mixed mpg of 19 in very conservative driving. I rarely ever get on the gas. The car is rated to get a mixed economy of 26. I see about 25 on the hiway at 60 MPH for long trips (2+ hours with cruise on). That's a far cry from the 31 mpg it is rated for. At first, I thought the bad gas mileage is b/c the car isn't broken in yet, but now I just turned 4000 miles, and one oil change, but I still get 19. No hills, few lights, no racing, just "going to church" driving. Engine seldom sees rpms past 2500.

To try to identify the problem, I tried driving my car in many different ways now since realizing the mileage wasn't getting any better over time, but there's almost no diff. I get 18 mpg driving aggressively and the same 19 mpg driving like most people do (spirited acceleration from a stop, and 75 mph on hiways.) Is this normal? The dealership tells me it is, but have reluctantly agreed to "look at it" for me. They already told me not to get my hopes up that they will find anything. A buddy of mind who is an auotmotive engineer and builds race engines for a living says the factory tuning is too rich, and that they should be able to "lean it out" on the computer so it uses a little less fuel. Is this true?

What have other 2.5-ers seen for mileage?

[nogears909]

27-29 in winter mostly city, usually get around 31 in summer

[LongBeachCoupe]

i dont think anyone with a 2.5 can get less mpg than i do... i have 20s that arent light, and a steel toe... Every stop gets followed by a full throttle... I drive 80% highway miles... 60 miles per day... and on the highway its btwn 65-85... I have yet to see the mpg drop below 21... Something sounds suspect...

[dldjros69]

http://forums.altimas.org/zerothread/325618

Mileage from another thread ^.

I have a 2.5 coupe 6mt and get about 27mpg combined.

I accelerate hard and drive faster 60 percent of the time.

[kuhan]

dude, if you read the other thread, my 2.5S got like 15 MPG for just normal city driving. Now i'm getting about 21-22 MPG in the city.Here's what I think it is the cause, just my assumptions.

1. My previous oil change, I brought my car to a Honda dealership for an oil change. They f**king overfilled the oil. I found out because I did an oil change recently, the old oil came out like almost 1.5 gallons (6 quarts). Those a**holes!!!! too much oil is not good for the transmission!!!

2. another thing is that I only drive my altima during weekends, so the car parks outside like 5 days straight in sub-40s weather. This could cause the some sorts of gas/air mixture issue or something wrong with the catalytic converter. ???

[adidas2go]

dude, if you read the other thread, my 2.5S got like 15 MPG for just normal city driving. Now i'm getting about 21-22 MPG in the city.Here's what I think it is the cause, just my assumptions.

1. My previous oil change, I brought my car to a Honda dealership for an oil change. They f**king overfilled the oil. I found out because I did an oil change recently, the old oil came out like almost 1.5 gallons (6 quarts). Those a**holes!!!! too much oil is not good for the transmission!!!

2. another thing is that I only drive my altima during weekends, so the car parks outside like 5 days straight in sub-40s weather. This could cause the some sorts of gas/air mixture issue or something wrong with the catalytic converter. ???

WHOA! Slow down angry. First, it is a bad thing that Honda put in 6 quarts, however, it has absolutely nothing to with the transmission. The a/f mixture caused by sitting in cold temperatures should be fine after the car is all warmed up and under normal operating temperature. Here are the 2 main reasons for faulty under fuel economy. Mass Air Flow Sensor, and o2 sensors in the exhaust system itself. Check these items for wire breaks, rigidity, and connection. If they all look good, then unplug your negative on the battery terminal for 10 min. This will reset the computer back to its original settings and erase and possible computer "hiccup" in the system. If all those fail, take it to Nissan and have them run diagnostic checks.

[sexybeasty]

4300 miles now and my highway is looking much better. I took a trip back home this saturday and on the trip down i got 30 (car told me I got 32.9, but I've learned that it inflates it by 2-3 mpg), and the way back I got 31 . My mixed is up to 20 mpg. If only I drove on the highway more New Fujita coming this week and I think I'm going to get the stillen exhaust. We'll see if that makes it any worse!

[adidas2go]

You know is doesn't actually measure you fuel trickle or anything, Its just a reading of how hard you push your pedal divided by time....and if you floor it 70% of the time and coast it the other 30%, well, the computer is going to give you an 18mpg reading....

[sexybeasty]

yeah, i know that's how it works. I feel like I idle the car along most of the time in mixed driving; i give it enough gas to get it rolling and let gravity do the rest. the car is great at coasting along at 45-50 mph with little accelerator pressure. The multi-function computer readout tells me I'm getting 23, but when I re-fuel (using the same gas pump at the same station) and divide miles driven by gallons used, it's usually in the teens. For instance, the last fill up (after my exciting 20mpg post) I used 12.3 gallons to go 188.6 miles. That's just over 15 mpg. Even when I fudge the numbers (round down the gallons used and round up the miles driven) to give the car the advantage, it still doesn't hit 16 mpg.

For anyone thinking there is something wrong with my math or the way I fill the car up, check this out. I tried this about seven fill-ups ago (which was like last week ...

To eliminate human error due to variances in auto-shutoff at the gas pump, I shoe-horned gas in at a trickle and literally topped it off until it poured out the fill pipe. I know it's not the best thing to do, but I needed to know if I was doing something wrong. I did this for two consecutive fill-ups and got 19 mpg. Again, this is during very conservative driving, and mostly at 45-55 mph on parkways to work and back.

I still love my car, but if I had known the 2.5 would get V8- like gas mileage during practical use of the car, I would have bought the 3.5. On my window sticker it says that in city driving, a car like this may not get it's rated 24, and that you can expect results between 19 and 27 city. To be truthful, Nissan should tell you that you will never (or rarely) see anything higher than 19, MIXED driving (I must mention I don't like in a city and see very few traffic lights). The only way I could get 24 mpg mixed with this car is if someone towed me to work and back while I idled the car.

BTW- Nissan looked at it and said the car is working perfectly.

[adidas2go]

Somethings f'ed up. Try disconnecting the negative for like 10 min. The computer will rest. My coworker has a 2.5 and he averages 26mpg driving semi-spirited

[Mr. Music]

...averages 26mpg driving semi-spirited

I get about 25mpg driving mainly in rush hour traffic. When I'm not stuck in traffic, I drive semi-spirited too. But man, with gas at these prices, I hope you get it fixed soon. I've already seen regular at $4.00+ per gallon.

[gregbid]

WOW- With 5000 mi. on my A/C-3.5- I average 20-21 mpg., and I do all city driving! The one trip I took averaged 25-27mpg. I've mentioned to a friend I should have gotten the 2.5, with the price of gas lately, but he told me the 2.5 did not get much better mileage, but there must be something wrong. I would definately speak to the dealer!

[Idok]

Be sure to check your tire air pressure. I run my stock continentals at 36 psi( know they're not very good but you run what ya brung). I would also jack up each corner of the car and be sure each wheel turns freely and easily (maybe a brake is sticking a little bit). Also try different brands of gas. I have found that Exxon gives me ~3//4 more mpg than cheveron and a little local brand is slightly better. Limit your warm up time to no more than 30 seconds unless it is REALLY cold,just keep the RPMS down until the temp needle starts to move up towards normal. If you are in cold weather country consider switching to a synthetic oil. It flows much easier and withstands contamination from short trips much better than conventioinal oil and retains its' viscosity better during high heat conditions.I also removed the air intake diverter which was placed during a recall and made my own so that the air is forced in to the intake box with a little force when I am moving. Don't know if it has had any effect yet.If you do a lot of modifications to the car this COULD affect mpg. Bigger/wider tires have a larger contact patch and thus will have more friction to over come. Also the bigger ties/wheels may be a lot heavier than stock.

I do about 85% rural highway driving and am getting about 35 mpg by the computer now that it is warm and about 29 in the city. In the winter (temps teens to high 20's and winter tires) I loose ~3 mpg

[sexybeasty]

Great Success!

I disconnected the battery cable for 45 minutes and since then I averaged 25.4 and 24.7 in the last two fill-ups using my calculations. BIG fricken difference from 18-19 mpg. I haven't changed my driving habits at all. Thanks for the tip!

btw- I stayed with 87 octane too and didn't go with 89 like I was advised by Nissan.

[sexybeasty]

oh, that 24-25 mpg is my mixed driving, which is mostly what I do. I haven't tried hiway but it HAS to be better than what I was getting. Doing another oil change this weekend, this time from semi to full synthetic, and taking a 2+ hour trip, so I'll get a great opportunity to see what my hiway mpg is.

[adidas2go]

Glad to see the it worked out for you

[Rev_D21]

This thread entertains me. Let me ask this, if you are so worried about fuel mileage why are you modding it? The mileage will do nothing but go down. So if it's low now and you are bitching, how much are you going to ***** when it really goes down after some tweaks?

[08Coupe]

If you "don't drive different" intakes and cat-backs will not hurt your gas milage at all!! Now performance tunes, cams ect are another story (and not available anyway)

[EzeebMOS3]

My car gets just about 20.5 mpg, i do mostly city driving though. However i do take trips that range around 80 miles every other weekend and still get the same gas mileage?? Whats up with that!?

[08Coupe]

If you reset it before your trip you will probably see 27mpg or so. It only averages it since the last time it was reset.....So a few good mpg trips wont change the average much. I get like 16-19 around the house and 26-27 on trips.

[sexybeasty]

thanks, I'm not really into modding cars anymore; besides it's an Altima, not an M3, so IMO it's kinda pointless. I'm more into bolt ons now to enhance slightly the performance of the car over stock since I don't want my fuel mileage to plummet and I like the car to be relatively quiet (until you step on it of course). I've played with cars my whole life and intakes and exhaust have a very small, almost imperceptible impact on fuel economy. BTW- my fuel mileage problem is fixed, evidently it was ecu related??? Dunno, but after disconnecting the battery to install my intake, it jumped up from 19 to 24-25 mixed driving back and forth to work. My highway is 29-32 depending on speed and if I use AC or not. I don't think the intake alone would have that kind of impact, so in my not-so-perfect experiment, I rule against the ECU.

Quote of the day:***If you can install it in your Grandma's Garage, it's not a Mod***

[tallnorwegianguy]

Got 08 Altima and getting 32.9 more or less

I run 40PSI in the tires , within manufactures tolerance and ride is almost the same.

I rarely use AC , which decreases MPG

I drive on HWY sometimes 80-85mph , mostly drive highway.

I use the cheap gasoline,never use premuim.

Nitrogen is suppose to increase MPG by 1-2 miles.

Happy driving.

[mrodrig2]

I get around 24-25 mpg just normal mixed highway/city driving. If I use my cruise control all the time I get around 28-29 mpg. I find that it's really hard to control gas mileage with the CVT. You have to be really careful and light with your foot.

[ESP]

Whoa...thread from the dead!

[Hussain]

i'm averaging 14 MPG now.... all city driving, and i tend to have a lead foot.... i think something is wrong with my car though. driving the same way, i used to get 18-19 MPG city... but the car drives like new with no loss of power, just wastes a good amount more gas now.

[rcboy514]

for the past two weeks now ive been getting 18.8-19mpg in town only......im very happy with that. I haven't driven in man. mode lately either which is why it's better i think. I used to get around 14-17

[Alien_Tracker]

What kind of rims are on your z? They're sweet.

[TomNJ]

I calculate my actual MPG on every fill-up (yes, I know ) on my '08 Altima 2.5SL with no mods and 33 psi tire pressure. After 17,600 miles and 40 tankfuls of 87 octane gas and mixed driving, my worst MPG was 20.4 and my best was 33.2 with an average of 25.6. Pretty much exactly what I expected. I would think any mixed average below 20 MPG indicates a sensor problem.

TomNJ

[Sentientbydesign]

This thread entertains me. Let me ask this, if you are so worried about fuel mileage why are you modding it? The mileage will do nothing but go down. So if it's low now and you are b****ing, how much are you going to ***** when it really goes down after some tweaks?

Not really true. My wife's celica has an AEM CAI and HKS axle back and gets close to or over EPA numbers. Is that the rule of thumb? No, but saying that modding absolutely reduces fuel economy is not true.