2006 G35X with horrible gas mileage

[catsnmusic]

Hi everyone,I'm new here, glad to be part of your great board.Last week I purchased a 2006 G35X automatic with 29,900 miles on it.Runs great and I love it.I have done the mileage calculations a few times correctly on the car whereby you top off the fuel tank, set the trip meter, drive it for a full tank and then refill it and see how many gallsons it burned. So for example I got 260 miles on a full tank and it took 16 gallons to top it back off. I'm only getting 10 MPG around town and 15 combined city/highway.I dropped the car off at the dealership this morning and it will be a few days before I get it back because they want to drive it some and see what they get for MPG. Anyone have any thoughts on what could be causing this poor MPG? P.S. I kept the highway at 55 MPH with cruise control and kept my city driving non-aggressive so that's not the issue.Thanks everyone,Mary in Boston
Modified by catsnmusic at 9:57 AM 1/26/2009

[marlin29311]

Air fliter, tire inflation, driving habits, gas type, etc....

It could be a world of different things - I would start by looking at the simple replacements - air filter, etc, and see what happens from there.

[smockers83]

As already said, it could be a plethora of things. However, with mileage that drastically off, it won't be just an air filter or tire inflation. There's definitely something going on.

Wait to see what they tell you and report back to us.

[kmckis1029]

got my best milage @80mph on highway in my g35x....

worst i ever get is 16mpg city when im playing with car...

Air fliter, tire inflation, driving habits, gas type, etc....

It could be a world of different things - I would start by looking at the simple replacements - air filter, etc, and see what happens from there.

+1

[zozoka1212]

As others said before could be too many different things. What's your mpg when you are on hwy and cruise control set to 55mph?

zozo

[pfarmer]

Air fliter, tire inflation, driving habits, gas type, etc....

It could be a world of different things - I would start by looking at the simple replacements - air filter, etc, and see what happens from there.

I had one car with a gas leak on the discharge of the fuel pump. Wasn't obvious since it only occuring with the engine running and it pointed straight at the ground. Amazing how much a pinhole gas leak adds up in gallons.

Perry

[catsnmusic]

Zozo, I got 16 MPG combined city/highway, and the highway was all cruise control set at 55 MPH. Also Pfarmer, if I had a pin hole gas leak do you think I'd smell it?

[tollboothwilley]

Only if you give it a chance to sit long enough...and then you might have to be outside the car to really smell it.

[zozoka1212]

It is hard to tell with mixed mpg. If you have mpg just on hwy with cruise controll that can tell more. It is possible to get low mpg without any racing. I myself guilty of it too. I warm up the car sometimes in work for 7-8minutes. Sometimes even more. Drive it only for 6-7 minutes to get home. Well with that it won't help. I can get 17mpg usually in "lite city driving". But I can get down to 12-13 mpg. If it was pure city it would be worst with heavy traffic. With the same way my wife gets much much better mpg.

I would try it only on hwy to see what you get. That would clear out if here is anything wrong with your car.

zozo

[catsnmusic]

spoke with the service rep about my '06 G35X with my alleged poor gas mileage (I say alleged because I could be wrong). He said they hooked my car up to whatever machine they have and no codes came up for any sensors being off. They said the air filter was fine as well. He said he then topped off the gas tank, reset the trip meter and drove my car to his house and back, round trip 62 miles which comprised of 60% highway miles and 40% city miles. He said he then re-topped off the gas tank today and it took 3.3 gallons to top it off. So the math on this (62 miles divided by 3.3 gallons burned) results in 18.7 MPG combined city/highway. Does this sound low or average? It's just weird that I couldn't get that. I got 12 MPG combined city/highway. His first recommendation is that even though my manual for the sedan says the car takes 87 octane (coupes require 91 for some reason), he said try bumping the octane up to 89 or 91 and see if my mileage improves. He said also instead of warming the car up for 15 minutes every morning drop it down to 10 minutes. He said these two things should help. How does all this sound to you veterans on the board?

[zozoka1212]

I don't think that's bad.

Summer gas should be a little better also. Maybe check the fuel you put in if it is premium and if it has ethanol or not. That could drop the mpg too.

When you buying tires check for the low roll resistance tires to get better mpg. Keep the tires properly inflated. Low tires can give you bad mpg and bad traction in snow.

zozo

[smockers83]

Warming up the car for 15 minutes is way too long for a couple of reasons, I'll get in to those in a little bit. But that's why you have poor gas mileage.

The gas mileage they got is much better and close to what it should be.

The reasons why 15 minutes is too long. First, cars should not be left to sit and warm up. This can actually be bad for the engine. You could cut the warm up time down to 2 minutes. You should let it warm up just to get the oil warmed up and circulating, which would be max 2 minutes (it's actually less, but 2 minutes is good). Secondly, the car heats up better and faster when you start driving it. The engine will heat up to the point where you can start using the heat within 5 minutes or so of driving. In the mean time, turn on those butt warmers.

Hope that helps.

Oh, and also, using the defroster constantly decreases your mileage because that uses the A/C system. Just throwin' that out there because I know a lot of people who do so and don't know.

Oh and welcome to NICO!

[zozoka1212]

If you see my post somewhere up I said I am guilty of it too with all the warm up time. I am just lazy to go out in the cold and sit in the car. LOL

It will definitely improve your mpg if you cut the warm up time. As smockey says.

zozo

[marlin29311]

Holy cow! 15 min warmup!

As smockers said, wayyyyyyyyy not necessary. Cars are not meant to idle - the whole point of warming up the car in cold temperatures is to make sure that the oil has time to flow properly through the engine, and to get the internals at a warm enough temperature to prevent metal bending and cracking. Generally speaking, once the temperature gauge on your dashboard starts moving, you should start moving your car too. That's an easy rule of thumb, but the 2 min is a good idea too. I generally do about 90 seconds, as at that point, the RPM's have begun to level off at a good idle speed.

Plus, the car should start blowing warm air at the point when the temp gauge starts moving - so you don't need to worry about being cold

[catsnmusic]

Wow, thanks everyone. I'm just so apprehensive about getting into a cold car. I didn't realize that the heat would start working so fast. I've been doing it this way for years (yikes). Also my heated seats seem to take forever to get warm. Ok, I get the message guys, I'll stop letting it sit for that long. I'll cut it way down.Mary in Boston

[pfarmer]

His first recommendation is that even though my manual for the sedan says the car takes 87 octane (coupes require 91 for some reason), he said try bumping the octane up to 89 or 91 and see if my mileage improves. He said also instead of warming the car up for 15 minutes every morning drop it down to 10 minutes. He said these two things should help. How does all this sound to you veterans on the board?

I have an 08 xs. I get between 19 and 21 on an average depending on the weather, real cold and it is on the lower side.

As far as the 15 minute warm up, not good. I have been through several cars now with up to 300+k miles on a couple. Basically I get in the car, start it up, as soon as it runs smoothly I drive slowly away. I don't take the speed up until the temp comes up and then I stay conservative until up to normal operating temperature. The only time I vary from this routine is if there is snow and I would have to work to get up my hill. In these situations I warm it up and then tackle the hill.

Perry

[kmckis1029]

my last combined mileage was 19 mpg... and thats with spirited driving... i measure the same way the infinity tech did...

[pfarmer]

my last combined mileage was 19 mpg... and thats with spirited driving... i measure the same way the infinity tech did...

Today I made a trip from Rainier, Washington to Lacey, to Shelton, to Bremerton, then to Port Townsend. On the way there I averaged 50.2 mph and got an average of 25.1 mpg. Temperature about 45 most of the way. I was actually a little surprised.

I have gotten 26 before but on what I considered a much better set of roads for it, basically nice and straight, few hills, etc.

On the way back I went a slightly different route. Port Townsend to Bremerton (twice forgot my debit card at a store in Port Townsend), then across the Tacoma Narrows bridge, then to Lacey and back home. Averaged 45 mph and got 23.9 mpg. Temperature average probably closer to 40-42.

I think this is actually pretty good for a car closing in on 3800 lbs. and 300+ hp. loaded with another 400 lbs. in it.

Perry
Modified by pfarmer at 11:39 PM 2/8/2009

[zozoka1212]

Yeah there is nothing wrong with our G. It is just warm up time city driving.

Last few weeks I've got like 13-14 mpg but I drove less time than I warm up my car. All city and short runs.

I went to Toronto 2 times this weekend back and for and ended up with 23.5 mpg. I pushed her few times. Was not using cruise controll and was never steady on the gas. Was going between 70-90mph. Sometimes less sometimes a little more. There was about 10 % city driving.

[pfarmer]

Yeah there is nothing wrong with our G. It is just warm up time city driving.

Last few weeks I've got like 13-14 mpg but I drove less time than I warm up my car. All city and short runs.

I went to Toronto 2 times this weekend back and for and ended up with 23.5 mpg. I pushed her few times. Was not using cruise controll and was never steady on the gas. Was going between 70-90mph. Sometimes less sometimes a little more. There was about 10 % city driving.

That is good to hear. As far as cruise control goes, most experts would state that it will hurt your mileage if the desire is maximum mpg rather than speed maintenance. I still use mine and let it follow the car in front of mine automatically maintaining distance in good weather conditions. On the other hand I am not yet a hyper miler, although I am tempted to try a few sessions with the car to see what actually is possible since we have the tools already installed.

There is a hyper miler close by that states that he can show nearly anyone how to safely get 50 mpg consistantly out of any car that is rated at 20 mpg.

Perry

[Poyzinous]

You guys may find it hard to believe, but there was, in fact, a thorough scientific study regarding how smart cruise control is, and if it is better than a person at optimum MPG. The results were surprising, but having extra knowledge than the average cubicle worker, I expected those results. Here it is: cars built in the 80's, not quite as good as a person. About 5-10% worse than a person. Cars from the 90's with computerized units, about the same as people, +/- 2%. But modern cars, like Nissan products, have electronic throttles and smarter programming, and have been found to be 4 to 8% better than humans, since we tend to drift off while driving after 30 minutes. Where a car's computer has no brain, it just does what it is programmed to do. We have to daydream about krispy kreme donuts and magically having 100 more hp on tap, speed limits increasing to 120mph and having a 6th or 7th or 8th gear with a .6:1 ratio for economic high speed driving, and having psychic control over other peoples bowel activity to screw with them at inconvienient moments. If your Infiniti has ICC, you're a lucky son of a Bi--ssnessman. ICC is wonderful. Anyway, if your car has bad MPG, make sure you aren't riding your brakes, sometimes people leave the parking brake(not E-brake, gosh darnit) on a little, or in the winter with the heat running, leave the AC on(I always turn it off), low tire pressure, obstructed intake/exhaust due to leaves, rust, curious animals, water, smurfs, etc. I only get 16mpg out of my G35x. But I have a heavy foot, and I'm mostly driving city. On a recent trip, I went a full 400 miles on one tank. With 3 people in the car, lots of luggage, and 70-75mph average speed on the highway.

[pfarmer]

If your Infiniti has ICC, you're a lucky son of a Bi--ssnessman. ICC is wonderful. Anyway, if your car has bad MPG, make sure you aren't riding your brakes, sometimes people leave the parking brake(not E-brake, gosh darnit) on a little, or in the winter with the heat running, leave the AC on(I always turn it off), low tire pressure, obstructed intake/exhaust due to leaves, rust, curious animals, water, smurfs, etc. I only get 16mpg out of my G35x. But I have a heavy foot, and I'm mostly driving city. On a recent trip, I went a full 400 miles on one tank. With 3 people in the car, lots of luggage, and 70-75mph average speed on the highway.

I have the laser cruise control in my 08 Infiniti XS sedan. I like it a lot with the exception that it appears to be a little sensitive when following another car. I wonder if that can be adjusted somehow. What it does is sort of pulse when following unless set at pretty much exactly the same speed as the car in front. In normal mode at slower speeds it tends to hunt a few mph at times but smooth at higher speeds. My 1999 Chrsler on the other hand maintains pretty much right at the set point up and down hills unless it is forced to downshift to maintain. At that time it hunts a little before settling down. The G tends to fluctuate more.

In the case of hyper milers the viewpoint is you maintain load and optimum engine speed and let the vehicle speed vary for maximum mileage. The cruise control will then work against you for this purpose. Some however state to use the cruise control to maintain speed on level roads, however to either use the up and down setpoints to maintain the best mpg on the gauge since many work well for effecient acceleration and deceleration rates or kick it off for going up and down hills.

The key piece of equipment in our case is our real time mpg gauge, a must have add on for most cars for hyper milers. I have experimented with the Chrysler and was able to get 30 mpg without too much effort which is up from about 22 driving normally over the same course.

I haven't paid that much attention to the AC on, but in reality after the car warms up is it really that much of a factor in cold weather? I figure it mainly comes into play with the defroster if it behaves like my other cars. In those cars the compressor rarely kicks in once the car is warm with the units in auto.

Perry
Modified by pfarmer at 11:51 PM 2/9/2009