whiteboyslo
OBS Enthusiast
So, I bought my 1993 C2500 Suburban last October and have been going through the whole truck. It has 147K miles and runs great, but the mileage STINKS! Today's fillup was best so far, but still just under 11 mpg. This was on a tank where the driving was predominately freeway at 65-70. I drive it like an old man, especially around town.
Everything done so far that could/should help MPG...
Possibly not helping....
The truck is running fantastically otherwise and definitely seems to have taken a liking to the minor exhaust work, but this mileage is brutal. Fuelly.com has me believing that I should be seeing low teens when it's mostly freeway driving. FWIW, the PO insisted he got 16mpg on a trip from CA to ID, but who knows how true that is.
Ideas?
Mike
Everything done so far that could/should help MPG...
- Spark plugs (ACDelco Rapidfire)
- cap, rotor, wires, coil (all ACDelco)
- All filters (including AFe air filter)
- All fluids
- Transmission serviced and checked out. Clean bill of health
- Brakes serviced (no dragging or binding)
- New oxygen sensor (ACDelco)
- New cat (CA, so can't remove)
- New Magnaflow straight-thru muffler
- New PCV valve
- Added the stock chin spoiler. Picked up 1MPG on the next tank, so this seemed to help a lot
- Steady diet of Seafoam in the tank. Injector spray pattern looks strong.
Possibly not helping....
- 265/75/16 tires. It's a highway tire, so tread is not aggressive at all but it is wider. Speedo reads very accurate per all the speed traps in my area.*edit* Just did the math. And adjusting for the tire diamater difference, MPG on the last tank was 11.1. Better, but still not great.
- Might be my paranoia, but I THINK my torque converter might not be locking up at higher speeds. Now that I have an exhaust loud enough to actually hear the truck (no tach), it sounds like the revs never drop once I get to cruising speed and don't jump up a bit when I roll into it once cruising like I think they should. Any way to check/confirm without having tach?
The truck is running fantastically otherwise and definitely seems to have taken a liking to the minor exhaust work, but this mileage is brutal. Fuelly.com has me believing that I should be seeing low teens when it's mostly freeway driving. FWIW, the PO insisted he got 16mpg on a trip from CA to ID, but who knows how true that is.
Ideas?
Mike
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