Hey there,

Recently bought my G - wanted to sleep well, changed all of the fluids (besides the transmission fluid, it was done at a reputable shop shortly before I purchased it) and the trans-axle fluid.

So, the fluids I changed: PS fluid (Dexron 3), Brake Fluid (Amsoil HP Dot3), Motor Oil (Royal Purple Full Synthetic 5w-30), Front and Rear Differentials (royal purple 75-90), Antifreeze (used Nissan specific Blue Peak + Distilled Water)

Spark plugs were the Denso OEM plugs, gapped at .044.

Currently running K+N drop-ins (brand new) but will be switching to AFE once they arrive.
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My driving habits haven't changed, I was getting 25 mpg prior to changing everything, now I am getting 18-20mpg. Very confused, I'm looking for some advice. Should I disconnect the battery to reset the ECU?

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Also, as a bonus (completely irrelevant): If anyone has this setup, please let me know: Post-MAF silicone intake tubes, drop ins, HFC + Catback + Tune please reach out I'd like to chat. (this is not my setup, but it is my intended goal w/ the car power wise).

 

That doesn't make sense. Is the idle high? The throttle bodies need to be removed to provide better access to the spark plugs, so you may want to run through resetting the following: Pedal Released Learn, Throttle Closed Learn and Idle Air Volume Learn

 

Based on YOUR calculations (miles driven divided by gallons used) or by the "car computer?"

 

The exact question I was going to ask.

 

I’m not sure I’ve ever done better than 20 mpg. Can you send me your old fluids and plugs?

Sea Stories

 

I can usually go 425-430 miles on a tank before the gauge touches "E" and the idiot light turns on. And on a 20-gal. tank you can do the maths. I rarely let it get that low but it is what it is. Depending on what mood the computer is in (and whatever nutty algorithm is involved when the data is polled by the amp), my MPG varies from 15-35mpg.

 

Are you stock? I see you are in MD, so relatively flat? Need to obey the 55-65mph speed limit as well since cops like to hide in the trees with radar (I grew up in MD)? Here in CA, if you stay a tick or two below 80mph and maintain a pace with the rest of the traffic, police generally leave you alone. We also have less than optimal "EPA friendly" 91 octane fuel, so faster driving on average and lower quality fuel for CA types.

In addition, we have alot of hills mountains here that the transmission doesn't always like to deal with, so city driving mpg isn't consistent. This was taken with a mix of city and "ideal highway miles" (coastal & flat, cruise control at 78mph, little traffic), 78ish miles to and from my destination in Irvine, CA.(taken when I was near the destination); I have one with better MPG (27mpg), but I had filled up prior to the same trip and had almost no city miles averaged in. I never run my car to empty, so the gallons/miles formula isn't as easy for me to use.

With no highway miles mixed in, I tend to settle between 16mpg (using DS mode, managing the transmission shifts with lots of throttle input) to 20mpg (deliberately not jabbing the throttle when taking off from lights, leaving in D).

Our transmissions seem to prefer being driven more aggressively, so I think its the weak link in city driving mpg. Note that in my 2004.5 G35 I drove from Dallas to San Diego (and vice versa) and averaged just over 30mpg in that car. All highway, 70mph average, super extra flat if you are familiar with the southern most route through the desert along interstate 10.

 

@socketz67 I’m stock except for Tanabe mufflers and a pair of resonators. I have a 6MT.

I’ve only put around 1,500 miles on my car. Since the car is new to me and I don’t drive much, I have a lead foot. I cruise at 75-80. I also hit stop and go traffic fairly often being in the DC suburbs.

I haven’t figured out my highway cruising mileage yet.

 

@Sea Stories I have the same exhaust setup. I also have silicon intake tubes with K&N drop-ins. All stock otherwise. 69K miles. I grew up in Morningside near Andrews AFB (PG county), then moved to southern MD when I was older. My side of the family is still spread throughout Southern MD. Navy brought me to CA, and my wife's family is out here as well. Your user name is of interest to me. Also a Squid? I personally have always thought that a manual trans should yield better MPG.

 

400 miles/tank? How? Are you 3.7 or 2.5? I don’t drive hard (often passed by suvs from lights) and I can get MAYBE 350/tank. Typically 300-330. I’d love to squeeze an extra 100 miles/tank!

 

400 miles is only 20mpg. New the mileage is rated at Up to 19 city / 27 highway. 20mpg seems reasonable if the car is running well and close to stock. How many miles are on your car? Mods? Tires? Aligned to factory specs?

 

Let's just say I have been accused by some of driving like a old fart.

 

The power steering fluid should be Dexron VI and the differential fluid 80W-90.