Abysmal MPGs and Other Headaches
My MPGs are rapidly declining. Started off around 14MPG when I bought it, and has been slipping slowly the last few fill ups, going from 13 last week and to an 12mpg this week. These figures I calculate based on the tripometer and gallons put in, not the trip computer which is always a gallon or so on the optimistic side. Since I bought this truck, I've done all the standard maintenance. Put in new plugs at proper gap (OEM spec Champions), new air filter (K&N I bought for the long life, not any expectation of performance gain), oil change, checked air pressures, and I use a bottle of fuel system cleaner once a month to wash out crap from the E10 fuel here. Fuel is 87 octane ethanol blended fuel. I don't even drive this thing that hard, to the point I baby it compared to other cars I drive, and it doesn't make a bit of difference. Cruises at about 1500RPM, rarely go much over 2200RPM when accelerating.
I was wondering what is normal for these to get? My driving consists of about two mostly highway trips of 30-40 miles, and 2-3 short trips of about 5-10 miles out in the country a week. Live up in PA, so air temps have been around 38-50 degrees when the truck is driven. Engine makes pretty of power still though and runs buttery smooth like a V8 should when cruising and accelerating.
The only issues I can think of are A: it idles rough occasionally, stumbling a bit, but I chalk this up to the low idle speed in newer cars (650RPM IIRC in this) as I've noticed it in a Suzuki too on occasion, and B: shifting from 1st-2nd, 2nd-3rd is occasionally rough, jerking the body/seat a bit (normal?).
Next, any suggestions to increase MPGs in these if what I'm getting is about normal? I'm getting a tonneau cover for Christmas (never thought I'd say that), and was considering some of these fuel saver tires when I get tires if the cost is about the same (and the ride/handling quality is not affected), but beyond that I'm stumped. I don't think a CAI is worth the money on these, as even though the air flow would be less restricted I don't feel it would be taking in any cooler air based on where the filter sits in most kits I've seen. I noticed a little boost when I did a glass pack and larger pipe in my old Corolla, but I really don't want to put some noisy muffler on this thing. I really don't want to take the plunge on O2 sensor(s) if it isn't throwing a code.
I'm just starting to get frustrated with this truck as for the money I'll have put into it by the time inspection rolls around I could have fixed the few nagging issues on my Corolla (a fluke CEL due to a buggy sensor that affected nothing, and gotten a pro repair on the rear defroster), had an entirely new exhaust system and CAI fitted, and had money left over for cosmetic work (Grille, lights, maybe a tint job). Thus far I'm in it a stereo (knew about it, and to be fair I splurged on that), fan belt (worn out and slipping), bumper jounce (obliterated), air filter (over spent and got a K&N but still needed one), spark plugs (knew), headlights (failing filaments and need aiming), oil drain plug (Cross threaded), and it will need tires (knew) and probably brakes (developed a vibration like a rotor is warped or needs machined due to being eaten into by worn pads) to get through inspection in addition to the crappier than expected fuel mileage (I was expecting between 15-16 at least). Also needs the rear bumper repainted and several rust spots fixed (three on the driver's door, one on the fender, which again I knew about) I got a deal on the truck but now I'm starting to see why...
Truck is a 5 speed auto, LSD, 4.7L V8, with (worn) 265 size all season Michelin tires.
Last edited by toyokota34; 01-16-2012 at 07:48 PM.