Last post on Mar 12, 2010 at 10:14 AM
You are in the Infiniti M35/M45
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Infiniti M35, Infiniti M45, Fuel System, Sedan
Aug 05, 2009 (12:01 pm)
I have an used infiniti m35 sport 2006. It currently have 67k miles and I have been suffering terrible mpg driving here in nyc. My city driving at best is around 10.5 mpg. My combine city/highway is around 16mpg. Anyone know what is wrong with my car? Is this normal for nyc driving? It is not even heavy traffic where I live. I bought this car to the dealer and they told me this is normal.
#80 of 97 Re: POOR MPG [infinitim35]
Aug 05, 2009 (3:03 pm)
What is your daily commute distance (each trip)? When you say city, was that like a stop light every quarter mile to half mile? What is the % for your combined drive, like 40% highway, 60% city?
Keep in mind, the M is very thirsty to begin with.
#81 of 97 Re: POOR MPG [shmang]
Aug 05, 2009 (3:28 pm)
I commute about 5 miles round trip. City driving as like stop light every block or every two blocks. It's not like one block the light will be green and the next block is red. It is consistent most of the time so I don't have to stop until like 5 blocks. My combine driving is about 30% highway and 70% city. Is this normal to get 10mpg? sometimes even 9mpg? I thought my fuel injector was dirty or something since it was a used car but I add some additive and it still didn't help much.
#82 of 97 Re: POOR MPG [infinitim35]
Aug 05, 2009 (4:31 pm)
In 2.5 miles (your one-way trip distance?), the car is not warmed up. Yes, the temp gauge will say it is, but it takes longer than that to fully warm up everything. In that time, the car will be using more gas. You're just getting to the point where it can start to hit its peak when you shut it off.
I have a 2006 M35x and my average tank mileage is about 20-21mpg, but I travel 19-miles, mostly highway each way to work. My mileage went up a little (maybe around 1mpg) when I switched to synthetic oil. I've had the oil tested periodically, and can safely run about 10k miles between oil and filter changes. You probably wouldn't want to do that with all of those short trips.
In NYC you might get run over by the cabbies if you don't accellerate fairly quickly, but it can make a huge difference if you take it a little easier, and don't brake late when you see the light is red ahead of you.
I'm seriously considering a new Mercedes E-class diesel. It should be great in short trips and on the highway (rated at 32mpg highway).
#83 of 97 Re: POOR MPG [james27]
Aug 05, 2009 (4:47 pm)
Well I don't live in NYC where there is a lot of cabs. I live in brooklyn which is more regular streets. I don't really think it has to do with the car warming up because from time to time, I let the car warm up for 5 minutes before I drive and it is the same thing. I drove 10 miles before I reset my computer and I am still driving at around 10 mpg city. I was thinking about getting a fuel injection cleaning and switching to mobil 1 to see if it helps. My friends m35x is getting about 13-14 mpg city driving compare to mine 9-10mpg.
#84 of 97 Re: POOR MPG [infinitim35]
Aug 05, 2009 (5:04 pm)
I believe your short trip is the key - if you let the car warm up (by not driving it), it just make your MPG looks worse, since it is calculated based on miles driven divided by gas used. When idling for warm up, you get zero MPG. I would let the engine warm up for 20-30 sec. at most and then drive moderately for a mile or so before go pass 3.5K rpm.
So, with your short trip and a lot of stop light, 10-13 MPG is not a surprise. I have a M45 and if I reset the trip computer at start up and drive the first 2 miles (45 MPH zone with basically no light), my MPG reading would be somewhere around 13, but since my commute is 22 miles one way, I normally get 17-18 without A/C and 15-17 with A/C.
So, short trip makes the car running at inefficient zone all the time - so it is not a surprise for your MPG. If you are driving a small I-4, this is not that noticeable, but for a big 6 (or 8), it is a very significant factor. Next time, reset your MPG calculation before hit a highway and run at least 15 miles and see what MPG you get. I will be surprised if it is not over 20.
#85 of 97 Re: POOR MPG [shmang]
Aug 05, 2009 (5:13 pm)
So should I even bother doing a fuel injection cleaning and switch to mobil 1 or live with the fact that my car will always average around 10mpg.
#86 of 97 Re: POOR MPG [infinitim35]
Aug 05, 2009 (6:58 pm)
If for fuel economy purpose, I would not do either. But for better care of the car, mobile 1 sounds like a good choice, but you still need to change the oil every 7500 miles or 6 month which ever comes first - consider your short trip and stop & go traffic, which is very hard on the engine.
What;s more important is: make sure you run the car for at least 15 miles one way once a month (or more often) with a few good accelerations. This will clear up all the carbon build up in the engine caused by all those short trips.
#87 of 97 Re: POOR MPG [shmang]
Aug 05, 2009 (7:09 pm)
Isn't it when you get mobil 1 you don't have to change the oil as frequently? Thats what the mobil 1 extended performance claims to do?
#88 of 97 Re: POOR MPG [infinitim35]
Aug 06, 2009 (9:25 am)
Inflated tire pressure to 34 PSI on my 2008 M35 increased my average MPG (combine) to about 18 - 19 and I also used Mobil 1 synthetic oil (5W30).