Well, I just updated my fuel log for my F-150...and I've hit a new all-time low, despite no change (or even modest improvment) in the "nut behind the wheel" skills.
13.3 MPG!
That's WITH EOC, DFCO-aware descents, timing red lights and not exceeding the PSL on highways. For the first time in ~20 years (even before I knew what hypermiling was), I'm UNDER EPA!
In the search for a mechanical problem, I've checked for vacuum leaks, read the existing plugs, performed a compression test, gapped and installed new plugs, and topped off all fluids. (Oh and I'm keeping the tires at 40 PSI.)
All tests were normal, zero carbon fouling, and 170+ PSI on all six cylinders.
I'm at a loss. I'm beginning to suspect a plugged CAT, simply because it would explain a steady decrease in economy (plus the fact that I lose power--seemingly--at WOT, and get an odd "pfft, pfft" exhaust sound: kind of like a headgasket breach, only less so.)
How would I test for this? I mean, besides just putting in a test pipe section for a couple of tanks? (Not that I'm terribly averse to that as a temporary diagnostic tool, mind you.)
Any other areas to look? Like checking timing?
P.S. I have won the missus on the idea of motorcycling
, so now the only use the truck gets is work-related, trips in averse weather, or for buying more stuff than would fit in a backpack. "Using a truck as a truck" would explain SOME drop, but I would still expect the I-6, MT, 2WD w/ 3.08 final drive to do quite a bit better...