Hello All -

I am experiencing a change in my average fuel economy over the past couple months on my '99 V6 4WD (80K). I was getting about 19-20 on the highway, 17-18 around town. I've noted about a 15% drop in economy, notably on the highway.

I've looked at prior postings, and am hoping for help to narrow down the potential causes:

TSB '99 Fuel Gauge Issue - I bought my Runner with 40K two years ago - how can I find out if the prior owner had the TSB performed? (my gauge does bounce around a bit).

New Tires - This summer, went with Bridgestone Duelers (265/70R), whereas I had 265/75s previously. My intuition tells me there really shouldn't be much of a difference, but can anyone confirm this?

Tuning - About a month ago, thinking this was part of the problem, I cleaned the MAF, throttle body, etc (still very clean from the last time I had done this), and cleaned/re-oiled my Amsoil filter. Additionally, my plugs (OEM) are 1 year old, and look nice and clean (I had expected them to be fouled up). I also reset the EFI fuse. No improvement.

One thing I didn't do was change the fuel filter, and OK, I embarrassed to ask, but where the heck is it?? Should I replace at 80K miles? Could this be the cause?

Thanks in advance for any guidance, or other theories.