Towncivilian

Napa Gold is identical to Wix. Bosch Premium filters are identical to Purolator PureONE filters.

Where did you get the 176 mile figure? I recall reading in the FSM a section detailing the "drive cycle" procedure for inspection readiness. I will try to dig that up later when I'm not so tired for you.

The color of oil means little, if anything. Engine oil is exposed to the combustion process and its byproducts, as well as blow-by gases, moisture, fuel, anything that happens to bypass your air filter... that combined with a specific oil's additive package can result in an oil turning black very quickly, or remaining a nice amber color throughout an oil change. Some oils even turn a funky shade of green after a thousand miles or so in some engines (Valvoline MaxLife IIRC). The only way to gauge an oil's condition in use is to get a used oil analysis, but unless you are trying to extend your oil change interval to maximize use of your oil this is not necessary. It is easier and not much more wasteful to just change around 5000 miles instead. Also, conventional oils today are excellent. See this used oil analysis of 10.2k miles on SuperTech 5W-30 in a VG30E in a '95 Villager with 230k. The oil's condition is stupendous for the high miles on the "lowly" store-brand oil.

Some more information which I copied & pasted from my reply on NICO: That suggestion is probably to lower apparent maintenance costs and downtime for the general public. Somewhere around 75% of a transmission's total lifetime wear occurs within the first 5000 miles due to break-in wear and any crud left over from manufacturing (the latter point is becoming less of an issue for newer vehicles since manufacturing processes are always improving). If nothing else, an early change such as a full fluid exchange around 5k miles or at the very least a 30k mile simple drain and fill is arguably the most beneficial for a transmission (or any drivetrain component; differential, transfer case, even power steering) to evacuate break-in wear and prevent wear from compounding. There is absolutely no reason not to change the fluid. The manufacturer is not always correct. The RE4R01A automatic transmission used in many WD21 Pathfinders was relatively weak to begin with at least when compared to the RE4R01A-HD model used in 2001+ Pathfinders and some other Nissan vehicles around those years. The RE4 in WD21s are known for failures resulting from debris and wear material clogging the cooler in the radiator (though in my opinion this is an unreasonable explanation) caused by lack of fluid changes. It is recommended to install an auxiliary cooler bypassing the stock cooler (or in-line with the stock cooler after thoroughly cleaning it out) as well as an in-line transmission filter to help prolong the life of the transmission.

Where does it say that ATF changes are not required? The factory service manual has a replacement interval of 30k miles. Warranty would be denied if this schedule was not followed with proper fluid used.

Not changing any lubricant is idiotic and neglectful. No lubricant can last the lifetime of a vehicle, only the lifetime of the manufacturer warranty which is their intent. Change it, there are no downsides. If it fails shortly after a change, it was going to fail anyway.

No benefit, change it every 5k miles or so and you'll be fine in the vast majority of cases.

Yeah, Nissan and Hondas share filters generally. If you can, try a different brand filter. Purolator or Bosch filters are great quality.

Do you use the Wix 1536 filter?

Yes, 10k km = 6213 miles, easily attainable using Mobil 1. There is nothing wrong with your oil change interval. Like I said, oil filter and viscosity (if you're really using 5W-20) are probable causes of your increased noise. It wouldn't hurt to check your power valve screws and apply red threadlocker to them too.

What oil filter are you using? Knocking sounds can be caused by certain oil filters. You're putting 5W-20 in a VQ? Too thin at operating temperature, our engines shear oil quite a bit. Get 5W-30 or 0W-30 in there.

Yep, W5W == 2825.

No problems with 1 GR-2 and 1 Excel-G, I have the same set up haha.

Ignition coil packs on 2001.0 model years are more prone to issues. If your manufacturing date is 08/00 or earlier you have a 2001.0 Pathfinder. 2001.5 and newer Pathfinders have different coil packs which are apparently less prone to failure.

Test your brake booster check valve, make sure it is sealing properly.

What? I've never heard of this feature. Maybe the brake booster loses vacuum when you start rolling backwards?

If your mechanic noticed the bright radioactive orange "LSD" sticker on your rear diff and didn't put LS oil or additive in it, he is an incompetent moron. Find a new mechanic.

The specified gap is 0.031 - 0.035 in (0.8 - 0.9 mm).

A 2825 bulb is the brightest replacement for a 168/194 type. Try it.

I get 16.75 mpg city 2wd, high 18 on the highway.

What fluid was used? Do you hear chattering when you drive a figure eight?

Did you get a #168 bulb?

Useless if the owners manual specifies 87 octane. Don't waste your money.

If you don't already have M1 75W-90 gear oil in your differential(s) (or a synthetic 75W-90) I would suggest doing so at some point since synthetic gear oil will warm up quicker and not be as thick when things are cold, resulting in a very small MPG boost. Leaking exhaust manifolds sounds like it could be causing problems as the replies above stated. You seemed to have already ruled everything else out that could be causing a massive MPG hit.

Your thermostat is fine, it's supposed to fully open at 176F. How long does it take before it reaches that temp from a cold start?