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Improving fuel economy / gas mileage in Gen3 T&C w/3.8L

3K views 14 replies 9 participants last post by  cuda2000 
#1 · (Edited)
I just picked up my first ever T&C, a 1999 (which seems to be the "keeper" year for this series...or is it not?) Canadian model "long wheelbase" edition (km speedo). Purportedly once AWD (has the badge), it was allegedly converted to FWD according to the seller. Vehicle was most recently in Nevada, then driven to Minnesota by a returning student (who said he bought it for that purpose as a one-way-trip hauler), whereupon I picked it up. It ran smooth and the oil looked like honey. Well-maintained and largely rust-free. Had some nicks and scuffs, but otherwise in excellent shape albeit shot AC and cruise-control out. Had to pull the radio fuse because a speaker was buzzing even when it was off. No biggies AFAIC.

What bugs me a little is the gas mileage. I'm getting around ~15c/21h in regular gas (87octane). -- My last van, a permanent blue-smoke belcher and oil burner with a 3.0 mitsy 6, still managed over 30mph despite wheezing its death rattles. The T&C, while having a larger-displacement 3.8 and a somewhat heavier frame, shouldn't, I think, be getting fuel economy like an early-80s eight-cylinder Buick, esp. with AWD disabled.

Compression seems to be good, as the thing has plenty of giddyup without me having to floor it. I don't think there are traction-control or caliper issues since it drives without pulling or noticeable rolling resistance. I also do not think it's running lean, because in other vehicles with that problem I've noted them straining while at brake and gutless during acceleration (neither of which are manifest here).

-- Tell me your tricks. (But please do not suggest spendy computer upgrades unless you personally have one and it made a substantial difference.)

Thanks.
 
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#2 ·
Depending on what your trips are will make a huge difference in your mileage. If they are all very short trips and the van does not get heated up during that time, it will not go into closed loop mode and remains "cold" all the time and the computer tells it it needs more fuel due to temperature. If your trips are 15 miles + then it will be heated up and you mileage will improve.

My wife drives our 98 T&C w/ 3.8L to the school and back and to Walmart and back or other short trips. She only gets about 10-12 mpg. When we take it on a trip (fully loaded) it gets about 18 MPG. The BEST we have ever got is 20 MPG. My 1995 Jeep Grand Cherokee with a 5.2L V8 gets better mileage than that around town.

These vans did not ever get 26 MPG.
 
#3 ·
Well, I'm driving it in the middle of a hot & humid summer up here, with most trips good jogs ~15 miles or so.

This thread seems to have a lot of odd advice, including one weird claim that removing the middle row of captains chair seats and moving the rears forward will improve economy by 5mg (!). ...except mine were already gone when I bought it. Or disabling traction control (how?) or "ESP" (huh? and how?). An ailing original O2 sensor at least makes some sense -- where are those located on the 1999 beasts?
 
#4 ·
I also have a 1999 T&C and your mileage isn't very far out of line with mine. A few comments:
  • We've had two 1998s, a DGC Sport and a T&C LXi, the DGC Sport would routinely get 24-25 mpg on the highway while both of our T&Cs are hard pressed to get 22. I have always assumed it was the extra weight of the trim, sound deadening, and even the seats (they are WAY heavier than our DGC).
  • Removing one or both of the rows of seats may improve fuel economy a bit, but 5 mpg, not going to happen.
  • The O2 sensor is extremely difficult to get to when the wiper tray is in place; it is behind the rear cylinder head almost directly under the firewall. If you remove the wiper tray, it is pretty easy to get to. That said, I don't think you'll get much by changing it as your fuel economy isn't really out of line.
 
#5 ·
I just picked up my first ever T&C, a 1999 (which seems to be the "keeper" year for this series...or is it not?) Canadian model "long wheelbase" edition (km speedo). Purportedly once AWD (has the badge), it was allegedly converted to FWD according to the seller. Vehicle was most recently in Nevada, then driven to Minnesota by a returning student (who said he bought it for that purpose as a one-way-trip hauler), whereupon I picked it up. It ran smooth and the oil looked like honey. Well-maintained and largely rust-free. Had some nicks and scuffs, but otherwise in excellent shape albeit shot AC and cruise-control out. Had to pull the radio fuse because a speaker was buzzing even when it was off. No biggies AFAIC.

What bugs me a little is the gas mileage. I'm getting around ~15c/21h in regular gas (87octane). -- My last van, a permanent blue-smoke belcher and oil burner with a 3.0 mitsy 6, still managed over 30mph despite wheezing its death rattles. The T&C, while having a larger-displacement 3.8 and a somewhat heavier frame, shouldn't, I think, be getting fuel economy like an early-80s eight-cylinder Buick, esp. with AWD disabled.

Compression seems to be good, as the thing has plenty of giddyup without me having to floor it. I don't think there are traction-control or caliper issues since it drives without pulling or noticeable rolling resistance. I also do not think it's running lean, because in other vehicles with that problem I've noted them straining while at brake and gutless during acceleration (neither of which ar0e manifest here).

-- Tell me your tricks. (But please do not suggest spendy computer upgrades unless you personally have one and it made a substantial difference.)

Thanks.
Driving style (no hard acceleration attemps), will improve fuel economy. I would make sure your tires are properly inflated and maybe try to over-inflate them (extra 2-3 psi).

Some people have issues with brake calipers that are dragging and that effects fuel economy. To test for this I would check the brake temps after a 20-30 min drive to see if the rear brakes are hot.

Have you checked the spark plugs and wires? Also check the air filter and I would make sure you clean the throttle body. I would also add some fuel system cleaner (Chevron Techron). Some people will say that you don't need fuel system cleaners etc. But given your results, I would give it a try.
 
#9 ·
The 3.8 was designed to run on "Regular" gasoline; using any higher grade will, if anything, reduce fuel economy. Needless to say, I use Regular (which has an AKI of 87 here in New England).
 
#11 ·
2000 T&C mileage

FWIW, my 2000 3.8L FWD gets a mix around Houston; usually mostly freeway into work, 50/50 going home.

With the AC off and taking it easy (not quite hypermileing) I can get 20-22 mpg. With AC running it's 19-21. My very best mileage to-from work hypermileing was 24 mpg.

On the highway with the cruise set to 60 and no AC I get 25-27 mpg on flats.

Running at 76-84 I get 19MPG with the AC on.

I'm running Michelins at 40 PSI. The van has 127,000 miles, no smoke, new plugs at 90,000. No other changes or "spechul" "upgrades" to any drivetrain components.
 
#14 ·
Shut the A/C off? I just took my son back to college with the 2.4L base shortie and only got 22mpg but that A/C was on with this heat wave. 16 gallons for 362 miles. Of course I was running a quart of lacquer thinner through the system as I felt a lowering in my throttle response. Cleaned it up nice. When I punch it on the on ramp it gets up and out of its own way now.
 
#15 ·
Recently drove 1600 miles road trip in my 97 caravan shorty with 3.3l. Averaged 73mph and got just over 20mpg with a/c on the whole way. With average 73mph, I was going 80mph+ most of the way. So mileage was sacrificed for speed. Van has over 200k miles on it and burns a quart of oil every 1,000 miles. It's my daily driver too. Original engine and transmission.
 
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