That's pretty much it. I used to get upwards of 32MPG on my '99 with a 3.2, now on my 02 3.5 I'm lucky if I push 27MPG. Though I know that's as much as the car is rated for, the difference in displacement is disproportional to the difference in mileage. There's also some pinging at low RPMs under load (slightly hilly terrain and/or running A/C), suggesting that perhaps the mixture isn't right, ergo my suspicion that there might be an O2 sensor issue. Is there any way to test these things? Can they be cleaned in any way? I'd like to avoid spending the $100+ it will cost to replace them, if possible. But if I pick up another 5MPG give or take, it'd pay for itself over time....or mileage is suffering and there's no other explanation?
Understood, but would those variables account for a 5MPG+ difference between this '02 3.5 and my '99 3.2 which averages 32MPG? Besides, I've replaced the plugs with NGK Lazers, cleaned the throttle body and ran two bottles of Techron through it when I bought her in April.That's actually more than the car is rated for. There's also 100 different elements going on here, from tire condition/brand/PSI, to spark plugs, etc.
I consistently get 27.2 MPG on the highway on my Special and a lot of the 3.5 guys considered that a miracle.
You may get a tad bit more but you won't consistently hit 30 on a 3.5. This isn't an economy car, plus the technology driving them was designed in 98.
Yep! There it is!FWIW, it has been said by others who know more about this than I do that the O2 sensors can drift a good ways from optimum oepration resulting in poor fuel mileage without setting a CEL/code.
But there's not a change interval official or otherwise. I'm still running my 2.7 on the originals with 250+k miles, and fuel milage is like it has always been (26-28 mostly highway).
So maybe until you get a CEL or mileage is suffering and there's no other explanation?