New Member looking for conservative improvements ('02 Maxima GLE automatic)

[Prophecy99]

New member here. I am liking everything I read on this site, very interesting and inspiring see what everyone does on here and no judging on what kind of vehicle they have. Whats also interesting is I am more than adequately educated in designing, constructing, and maintaining environmentally sustainable Buildings and the practices associated with that. But when it comes to the advanced practices i have been reading about here, I am not extremely familiar with it when it comes to vehicles. I am knowledgeable with cars enough to have already modified my car to be one of a kind and enjoy it more than the average driver. Such as suspension, engine performance, lighting, and handling etc.

2002 Nissan Maxima GLE Automatic 5 SPD. i will post pics after 5 posts.

I am interested in getting the best(or better) gas mileage i can get with out going too far, in other words I want my eco mods to be subtle. I want to keep my car fairly the same on the outside, which may or may not be my down fall to actually reach my 28-30 mpg goals. EPA 17 city 24 Highway. Which I have read in the Maxima world people with autos can get up to 22 city 28 highway. on average at best.
Recently i have been driving wholly concerned with only minimum fuel consumption (fc) in mind. Never going over 2,000 rpm, and staying under 60-65 at high way speeds.
I recently have been manually tracking my MPG (since the ECU is usually ambitious to the point of 3-4 MPG higher than actual) and have gotten at best so far on 90% highway trips 23.78 mpg. Which isnt bad considering that was also before I changed my so called lifetime fuel filter. It is known in the maxima world that changing this fuel filter is recommended even though its supposedly lifetime. I am really excited to see how the change helped. By judging how much I have traveled on my current tank after the fuel filter replacement alone I can easily say i got 2-3 mpg better. Will post updated mpg from that tank.

List of Eco related Mods
-Lowered 1.4 all around
-42 PSI all around
-Driving Habits modifiied/regulated for best MPG at all times
-Regular Maintenance done (ngk platinum spark plugs, filters, fuild changes/flushes, all with in 15k miles)
-Front Lip Spoiler
-No rear spoiler (dont no if bad or good for eco)
-No aftermarket exhaust, or air intake


What are some other things I can do to reach my conservative 28-30 mpg goals? I know my air filter could be changed but i have been blowing it out every so often.

Some things that caught my eye are under body aerodynamics, grille blocking, and rear diffusers. All pretty subtle if done right. i also have a grounding kit, which has helped idle, shifting, and electronics very nicely.

Thanks in advance for any info or advice!

[Prophecy99]

another eco mod I just noticed I have
Advanced Ignition Timing 2 degrees.

I also use 89 octane, and IIRC octane usually dosen't effect mpg as long as your engine isn't pinging.

[MetroMPG]

Welcome to the forum.

I know my air filter could be changed but i have been blowing it out every so often.

Believe it or not, a dirty air filter will have a little to no effect on fuel economy. Long gone are the days when a dirty filter accidentally resulted in an enriched air/fuel mixture (pre-computer monitoring - e.g. OBD). Even with a dirty filter, at part throttle openings (ie. at low/mid load engine operation), the throttle plate is the major restriction.

Some things that caught my eye are under body aerodynamics, grille blocking, and rear diffusers. All pretty subtle if done right.

Those all sound reasonable. I'd start with the partial grille block (easiest), and monitor engine temps as you progressively tune it for best effect. Do you have a way to accurately monitor coolant temps (digital gauge)?

[Prophecy99]

that's amazing i never heard that, you always hear advertisements and the auto communities stating a dirty air filter is bad for your mpg.

Also i have a good feeling my butterfly valve of the throttle body is dirty and shows all the specific symptoms of it (immediate surge of rpm after cold start ups, and goes back to regular idle rpm shorty after, and a medium rough idle in traffic and Park). Do you think that would effect mpg?

I have a engine coolant temp gauge, so yes i can monitor how the blocking works. My quesiton with grille blocking is is it still effective if I put it directly behind the actual grille and infront of the radiator etc? In other words I want it to be subtle and not directly on the outside of the car. Again aesthetics on this car is more important to me than a few % of aero. I would think any kind of block is better than nothing.

Thanks for the reply. I am starting to see you're posts everywhere.

[MetroMPG]

Blocking directly behind the grille will work nearly as well as in front. Some members do just that for aesthetics.

As for that throttle plate, makes sense that a clean intake would perform best in all regards.

I'm a bit surprised that you're only getting 24 mpg while keeping your speeds down to 60-65. I'd think you'd be exceeding highway EPA by ~5-10% at that speed (assuming you're doing 90% highway).

[allenh318]

Try changing oil to a synthetic and go with the 5w-30, which I believe is what your car recommends. Can also go with synthetic trans fluid, check all brakes to make sure they are adjusted correctly and not hanging. While checking brakes, check bearings and axles greased properly. Next, you can seafoam the engine to make sure your fuel inj is working properly. You can also spray carb cleaner on the throttle plate if you are concerned about it not working properly. I have a '95 Maxima GLE, did all of these mods as well as complete tune up, and get 26-28 regularly out of it.

[GRU]

check your wheel alignment

[allenh318]

Good point on the alignment, also pump your tires up to sidewall max and possibly get low rolling resistance tires, that should not change the look of your car much.

[Prophecy99]

Update: got a wheel alignment, mounted balanced all tires.

I am running on heavy aftermarket 18" wheels but i like them too much and am willing to take the little downfall from them, which I don't really see much. I only use them in the summer months and the blends fuel in the summer months make declines in efficiency a wash.

I have been gettin 24.8 MPG and 24.9 MPG on a few tanks now with 50/50 city highway. I am quite happy seeing 25 mpg but would like to reach 28-30 if at all possible with a 50/50 city highway run.

I also have a rear brake issue with them making contact at all times, so that has to be hurting too.

[Prophecy99]

do you guys think going from 42 PSI to 44PSI will really do anything?

i am also researching under body aerodynamic material to make a rear diffuser.