Gas guzzling 1993 Chevy Lumina, need tips
 

I've got a 1993 Chevy Lumina with 3.1 liter V6 and automatic transmission. I've tried my best to drive conservatively but the best I've managed with the thing is 24 mpg with mixed city and highway driving.

One thing that's weird about this car is it seems to coast better in drive than in neutral. When I put it in neutral it slows down very quickly. I've never had a car that does this. As soon as you put it in neutral it feels like when you let off the gas in a high compression car; instant deceleration. Any ideas why it does this? The brakes are all fine, no dragging brakes, the wheel bearings are fine, too. And I can't understand why it coasts just fine in gear.

Any ideas on what I can do to increase my fuel mileage? I already shut it off at stop lights, keep my tires at max sidewall pressure (40 psi) and drive as conservatively as possible.

Don't accelerate too slowly, you want to get the torque convertor locked up fairly quickly, get the engine to about 3000 rpm, let off to get it to shift, and reapply until up to desired speed. The Malibu 3.1v6 did coast almost the same N or Drive, rpm did drop a little more in Neutral.

Drive like your brakes are broke and saving them just for emergencies.

MPG instrumentation? Fuel log?

How are you doing vs. the combined EPA rating?

The car is OBDI, I'm not sure if there are any instruments out there for cars this old. I just compute by hand; fill the tank, record mileage when filled, compare miles at next fill up and how many gallons to top it off then compute miles per gallon. I think the EPA estimate was around 23 mpg highway if I remember correctly. I'm just slightly beating that. However, I can very easily beat the EPA rating on my wife's 2007 Toyota Corolla (auto trans) with no problem. It's rated at 34 mpg highway and I've consistently been able to achieve 42 mpg and higher on rare occasions.

My Lumina just doesn't seem to be able to do any better than 24 mpg and I'm wondering why. I'd think I should be able to achieve upper 20's mpg without too much effort, but I can't.

You're in luck: there is an MPG gauge for non-OBD-II cars. Check out the MPGuino. If you can find a fuel injector wire and the VSS wire, you're in luck.

Can't beat instant/resettable trip average fuel consumption feedback for fine-tuning your game.

The coasting issue does sound very strange. Wild guess: maybe the car's feeding in a small amount of power when you lift off the accelerator at speed for smoother transitions? A MPGuino would confirm/bust that lame-brain theory.

Does the engine seem to labor at idle i.e. is an accessory drawing too much power? Otherwise I'd think it would be a dragging brake(s) or maybe an IACV that is acting strangely.

A trip odometer would be great, since the car doesn't have one. I hate having to write down the odometer readings between fill ups, so much more convenient to just use a trip meter.

As for the weird deceleration when shifting into neutral, the only thing I can think of is maybe the car shifts out of overdrive for some reason when shifting out of drive. Not sure, it really is odd. I've never had a car that did something like this.

Idles fine, and I've checked the brakes and wheel bearings. Maybe it is IACV, I'm not sure.

Where can I get the non-OBDII MPGuino?

You've got a 2 ton mid-sized sedan with a V6 and auto transmission. According to fuelly.com the average reported MPG is under 20, so at 24 I would say you are doing pretty good! Consider pumping the tires up to 50 PSI. The biggest gains are achieved up to 50 PSI, so 40 to 50 could see a little improvement. Also consider some aero mods and weight reduction.