Gas Mileage Woes

So I know that the wagons are capable of getting upwards of 23-24 mpg but I have not been able to see anything close to that number in my daily driver. On my last trip home from Rochester to Syracuse and back, I was only able to get 18.9 mpg (This includes a small amount of city driving while in Syracuse).

My last tank while driving to work all week was 15.8.

I know there are a lot of variables in this but I feel I should be getting better mileage. A part of it could be my driving habits.....

I don't know when the last time it had a tune up. Currently have 105,xxx miles. Wagon is a tow pack, mechanical fan, 2.93 posi rear. Fuel filter was replaced at 90,700 miles.

What else should I be looking at to improve mileage?

Did you mileage go down after you put the exhaust on? I know My mileage has gone down a bit in the OCC since the muffler delete mod....and it is all my foot's fault.

My wagon gets around 12 in the winter and barely 21 on the highway in the summer. The lucky schmucks who get 27 are always the ones posting.

0. Fuel injector cleaner.
1. Oxygen sensors.
2. Replace your ignition coil with an ACDelco model
3. Replace your coil wire.
4. Replace your spark plugs - but check the gap on the current ones first. Take a look at all the driver's side plugs because they're easy to get to. If the gap is less than 0.060", then they're probably fine.
5. Replace plug wires only if you feel so inclined.

All the normal stuff first. Air filter, plugs, wires, cap, clean TB and MAF, clean and function test the EGR etc. Try to default the computer to base tune and let it re-learn from scratch. Get a scan tool and check O2s. Another area to look at is the o-rings on the injectors and while your at it do a few double doses of injecter cleaner.

Some other factors can include the mechanical fan (if partially engaged can suck up 2 to 3 HP...11/2 lbs. of fuel/hr.) and check to make sure the torque convertor is locking up. Also check to see if odometer is accurate (GPS will do) and if any brakes are dragging (doesn't take much).

After everything else you can look at a custom tune.

Bill

brokecello wrote:

Did you mileage go down after you put the exhaust on? I know My mileage has gone down a bit in the OCC since the muffler delete mod....and it is all my foot's fault.

I call that "NES" (New Exhaust Syndrome) Happens to the best of us after new exhaust is installed

Like I said, could be my foot but on my highway trips I cruise at 72 and don't touch it.

Thanks for the list of things to start looking at!

do you have OE quality plugs? When I did the tune on my rmw I was broke and bought copper plugs. I REALLY think that is why I'm running rich all the time now as the spark isn't strong enough to burn all the oxygen, then the o2s see that and dump more fuel in. I really noticed it when I switched to a K&N set up and lost 2 MPG! I've been too lazy to swap out the plugs and go platinum again but really should as they'd pay for themselves if that fixed my issue.

btw I get 15 around town and 20.5 tops on the highway with a light foot. 2.93 tow pack
my 92 lo3 gets 18 around town and 26 on the hwy!!! 2.73 rear

Plugs don't affect spark quality as long as they're fairly new and the gap isn't too far from spec. Plugs with blunt, rounded edges will not produce as good a spark as plugs with sharp edges on the electrodes, but all new plugs regardless of brand have sharp edges where it counts.

Guys, put a new ignition coil and coil wire on the car if the original hasn't been replaced. Coils wear out over time.

Based on a simplistic formula for wind resistance. The difference from 65 to 72 is 22% more resistance. If you set cruise at 65 instead of 72,then 18.9 MPG plus that 22% nets you 23 mph.

Shammoo's MPG is less than 12 around town, not fully tuned yet, but that's the nature of the beast when it's a large carnivore are on the top of the food chain. Less advance on the ignition curve usually helps mileage but hurts performance.

My Marshmallow has never been one to get good mileage either. I average 17-19mpg with mostly back road driving, and I'm happy with that. On the highway it gets 20-21mpg. Morticia and the Fatwudy got 24-25mpg on the highway. Not sure why this one is such a pig. I've done the basics, tune-up, plugs, etc. Not sure if I've done a coil. I'll have to swap it if I haven't. I know a lot of it has to do with the crappy ethanol gas we have to run on now. I remember when that switch happened, I lost like 3-4 mpg in all my cars at the time.

Bill's post remined me of this : On long road trips--- out of state --- I have noticed a drastic reduction in fuel economy when I have filled up with gas that had a greater percentage of ethanol. (well it seemed drastic to me! - definitely noticeable in any case )

Quote :

Guys, put a new ignition coil and coil wire on the car if the original hasn't been replaced. Coils wear out over time.

ESPECIALLY if you have a 94 or 95.

jayoldschool wrote:

Quote :

Guys, put a new ignition coil and coil wire on the car if the original hasn't been replaced. Coils wear out over time.

ESPECIALLY if you have a 94 or 95.

THat may be my problem. It only has 174K on right now
When I run datamaster on it (94 OBDI) my fuel matrix is rich across the board which I took to mean unburnt oxy causing the sensors to dump more in. as weak spark (coil) would def explain that!.

i just checked the milage on the new 96rmw i got 22 mpg on highway home from ny.this week driving back and forth to work all city driving 16mpg. the old 96 was a real pig it only got around 13 mpg city with wife driving it. i did not drive car much but she was always bitching about having to put gas in it. had it emissions inspected in sept and the garage said it was running in excellent condition as all numbers were low. both cars are towpack with 2.93 gearing

i just checked the mileage on the new 96 rmw and the highway was 22 mpg and this week of driving back and for to work of all city driving was 16 mpg.

the old 96 rmw was a real pig deb was always bitching about having to put gas in it . when i checked the mileage iwas avraging 13 mpg city highway was around 24 mpg . i had the emissons inspection done in sept the gargare said the car was running perfect that all the numbers were low with no need for any adjustments. so i do not know what was the problem with it. i did not drive it much.