Hello Daniel, i read all of your threads and believe you have the knowledge to answer this question objectivly.

I would like to improve fule mileage. I was under the impression that spark plays a role. If i upgrade to Bosch Platinum + 4 plugs which wire set should i install to compliment . And would this help or hurt performance?

Thanks for your time..

 

The VQ30DE engine used in 4Gen Maximas uses Coil On Plug ignition. There are no spark plug wires.

 

What mileage are you getting now? The EPA "window sticker" fuel consumption figures are not advertising puffery, they are realistic and achievable. My '99 GXE 5-speed routinely delivers better highway mileage than the EPA number.

If your '99 Maxima is getting substantially worse mileage than the EPA numbers there may be a correctible defect in your car. Excessive fuel consumption can be a malfunction symptom, just like hard starting or stalling or misfire.

Is your '99 still under warranty? If so, give the dealer an opportunity to evaluate and repair your car as a no-charge warranty service. If you are not under warranty we can exchange further fuel economy ideas in this thread.

 

Daniel, the Maxima has 52k on it. I have a 100k extended warranty but would not bring it in for this. The car is going in for a tune up. ( Local import Garage) Mobil One oil, New oil filter, Fuel Filter, Plugs, K&N Air Filter, and check the clutch fluid. I believe this should improve things for me. The approx mileage varies. 14-16 MPG city 16-17 highway.. I have read posts that members get 400 miles to the tank. I have never gotten 320.

Thanks for the wire info..is the stock wireing enough for the Bosch Planinum +4 plugs?

Anything eles i could try, outside the dealer..

 

Miles Per Tank is an inaccurate measure of fuel consumption. Miles Per Gallon is preferred. 16-17 mpg on the highway is much lower than expected. The EPA number for highway travel is 27 mpg and my Maxima gets 29-30 mpg.


Your car is using too much fuel. Four possibilities exist:
- you are burning it
- you are leaking it
- someone is stealing it
- gasohol vs gasoline


Burning it...
- fuel injectors are sticking open
- "tired" Oxygen Sensor
- bad fuel pressure regulator
- obstructed fuel return line
- bad Engine Coolant Temperature Sensor
- stuck-open thermostat (engine never goes into closed-loop mode)
- automatic transmission defect (never shifts into fourth gear) (This is included on the list for completeness. I realize your '99 SE is a 5-speed.)


Leaking it...
Search for fuel leaks by sight and odor. However, some fuel leaks are so
tiny that they escape the human senses. One way to find them is to have
your mechanic use his exhaust gas analyzer. Switch the tester to HC
(hydrocarbons) and then pass the probe along the entire fuel system,
starting at the fuel tank, forward along the fuel lines, past the filter,
all around the engine, then along the return line and back to the tank.
The tester is far more sensitive than the human eye or nose. When the
probe passes near a tiny leak the reading will abruptly increase.


Stealing it...
Perhaps someone is stealing small quantities of fuel, not for its financial
value but as a prank. Install a locking fuel filler cap.


Gasohol...
- You may have not realize that you are using gasohol.
- You may live in one of those regions which is required to sell oxygenated
fuel during the cold weather season.

Now that MTBE is in disfavor, gasohol is the most common oxygenated fuel.
Alcohol has a lower energy density than gasoline.

 

Yes, the stock wiring is adequate. However, spark plugs for Maximas is a controversial topic. Some owners report bad results with any plug other than the stock NGK platinums. Bad results such as a ragged idle or stumbling on acceleration.

Spark plugs are not a limiting factor in performance or economy. Your fuel consumption problem lies elsewhere.

Has your Service Engine Soon light ever gone on? If so, what repairs were done?

Are there any other symptoms aside from excessive fuel consumption?

 

Gasohol...
- You may have not realize that you are using gasohol.
- You may live in one of those regions which is required to sell oxygenated
fuel during the cold weather season.

I live in NY , Long Island. I believe the gas has an oxygenated system. How does that effect milage?

No theft ...But i would like to see someone try..hehe get to use my lincoln navigator to run them over.

No Leaks, checked for that when i bought the car

Burning...Will have the garage change the o2 sensor..

Thanks again.

 

The government says gasohol increases fuel consumption by 3%. Many motorists say the truth is more like 10%. However, this does not (by itself) explain your Maxima's excessive thirst.

 

In this post: http://216.122.219.59/forums/showthr...oke#post236361 Dave B said:
I get 27 mpg overall (60% city/40% highway) with many 40-80mph blasts.

There has to be something wrong with your car to cause such excessive fuel consumption.

 

A few questions for bluefish. You live on the Island correct? How is your commute? Stop and go traffic, steady cruising, and mix between the two? I would assume a bit of stop and go. How long are your commutes? A short commute will eat gas at an incredible rate. I have a twenty mile commute from/to work and am getting about 380 miles per tank now vs. about 200 per tank when I had a 2 mile commute (I know Daniel). Think more the situation and not the car (for your sake).

 

My 97 SE 5spd gets 24 routinely (68K). Thats driving in town and on the HWY. I occassionally "goose" it but usually pretty sedate. BTW, when on the HWY it's cruise control at 80 MPH.
Spark plugs....just changed to Bosch Plat +4s. No problems, purrs like kitten plus AUTOZONE had a $10 rebate with them .
If you know what a wrench and a screwdriver "IS"....try doing this stuff yourself. It's not rocket science to turn a wrench and drain/refill oil. You'll save a ton of money, you'll get the oil/parts that YOU want and you'll come away one happy guy. Changing the spark plugs. Well you will need to get a ratchet set with extension, torque wrench ($30). Believe me, the money you spend for tools will be cheaper than taking it to the dealer. TRY IT, YOU'LL LIKE IT.

 

I agree wholeheartedly.

The man who does his own maintenance
- saves money
- learns more about how his car works
- takes pride in his skill and self-reliance

You may find you can change your own oil in less time than it takes to
- drive to Quicky-Jiffy-Iffy Lube
- wait your turn
- wait while they do the work
- drive home

 

Sort of OT:
Went to Walmart last weekend.
Felt sorry for the cars owners left there lining up for service. About 15 cars in line. Imagine 15 start ups and shutdowns by strange hand just to get to the lift.

 

Thanks for all of your Comments.

Regarding my commute. I go about 4 miles to work each day and about 100 miles on the highway when I travel ( often twice each week, and on the LIE I often run at 80-85 mph)


I regret that I used to enjoy working on my 72 ford gran torino, 69 mustang, and other classics. I have taken auto shop 15 years ago in High School. However I am finding my time is more valuable at work , ( the service station will drive me to my office and pick me up when my car is done. ( that's because they have handled all of my " Newer cars) My 98 Lincoln navigator just turner 55k so I see them a lot, as well as for the fleet of construction trucks we own. I do agree that The man who does his own maintenance
- saves money
- learns more about how his car works
- takes pride in his skill and self-reliance

However not having any knowledge of this car, and the time issues I will leave it up to professionals.

As for the mileage. I will report back after work has been completed to see if I notice an improvement.

Thanks again for the information and facts.

Peace,

 

I'm on the way western end of your island (Brooklyn), and that 4 mile drive kills the milage in cold weather. The engine runs very rich until it comes to full operating temp (this takes longer to reach than the temp guage to come up. In 4 miles, it may never reach it. The gas milage ratio between long hwy (75-80) to cold short trips is 2:1 with my 90 GXE.

 

I'm just blown away by how many VQ Maximas get bad gas mileage. I've read this type of post many times before. How are you guys figuring your mpg? This is what I do. Fill the car up and set the trip odometer to 0. On the next fill up note the miles and divide by the amount gas added. Is this what you guys do? I find it amazing that a stock VQ is getting 14-15mpg in the city. My oldman's 96 Tahoe gets 14 in the city and 18 on the highway. Like I've said before, I "ring" my car out a good bit and use all the rpms. On a typical day, I make 4 trips. I make 2 8 mile trips (work) and 2 two mile trips (lunch).


Dave

 

I usually get between 20 and 22 mpg. Usually around 320-340 miles per fill up, and I usually can only fit 16 gallons in my car.

This seems a little on the low side to me, but I figure that it might just be because of a more "agressive" driving style.

The thing that bothers me, is that even on an all highway drive I can't seem to get over 24mpg going 75ish (~3200 RMP's). I guess if I drove a little slower I would get better numbers on the highway.

 

ejj5875: wow your engine is spinning at ~3200rpm going at only ~75mph? Mine doesn't reach ~3000rpm til I hit ~87mph. I have an auto, what's yours? I was even thinking about getting a y-pipe to help with cruising at highspeed while keeping the engine down by 100-200rpm since I roughly mantain that speed over 40 minutes each way on my commute to work.

 

Think that I'm doing about 3200rpm also at 80. Course I do have a 5spd. Must be a bit different gearing. At any rate, think I'll keep the 5spd

 

Short trips can make a huge difference in mileage. My Continental gets 26 on the freeway, but with all of my short trips to school and drive-thrus (probably about 2 miles round-trip) I get 11 around town.

As for my Maxima, I get about 20 around town, doing the same short trips with a heavy right foot. On the freeway I've gotten 29 going 75-80, or 25 if I'm going 90-95. 23 with the bikes on the trailer.

I think I might have some fuel leakage issues though. My car hesitates a little when I nail it from a stop, and I can smell the exhaust burning rich. Kind of reminds me of our old Plymouth Satellite when it was cold.

 

I have a 5sp. 3200 was a guess, but I'm 90% sure that its right. I will keep an eye on things on my way to work this afternoon and let you know.

Mods don't effect the RPM's at a given speed in a 5sp.

 

I have a 95 SE 5sp. I do a lot of highway miles and consistently get over 400 miles to a full tank.

 

my new job lets me drive 44 miles to work each day. i have kept a logbook of every fill-up that my car gets (2.5 years now!!) and i can usually get at least 25mpg, up to 28mpg, and as low as 21mpg. i think the difference may be due to the driving conditions.... whether i get stuck in rush hour, or whether i feel like revving the engine a lot. it may also be due to the type of gas, although i have not been able to correlate whether any brand of gas is better then another.

i measure the mpg by resetting the trip odometer each time i fill up and making the calculations.