2006 Nissan Pathinder, 163K miles.
Engine runs great in general, zero oil burn, MPG is 14-16 in city, around 18 highway.
The question I wanted to ask: I think my highway MPG is on low side, it has to be around 20-22, wanted to ask for ideas.
Some related car history.
Spark plugs are new/OEM, fuel injectors were recently removed/cleaned with a solvent, checked for a flow pattern to be consistent. Air/Fuel ratio sensors are new/OEM, same for downstream 02 sensors. Both catalysts are “fresh” (one is a shiny OEM, replaced by prior owner, one aftermarket, replaced by me), so restriction is out of question.
I also tried replacing MAF sensor (just had a compatible OEM unit laying around) and after re-calibration it did not change a thing, so I’m back to original MAF.
Timing chain tensioners were recently replaced (dreaded VQ40DE engine “whine”), valves were adjusted in the same time.
I know for sure that fuel pump back-flow valve is dead, as sometimes I have to “prime the pump” if vehicle sits long with nearly empty tank.
I checked the fuel trims, and this is something of suspect.
I have long-term trims around 9.0 - 9.5 (two banks) and short-term trims were 11.0-11.5 at idle.
I was always under impression that trims are supposed to be much closer to zero, are they not?
Once again: car drives fine, no power loss what I can observe.