1st tank of gas: 34 mpg!

[mrmojo]

I know, for a lot of y'all, 34 mpg isn't much at all, but for me, it's huge! I bought this 2002 Chevy Prizm a couple of weeks ago, and I just drove my fist tank with it: 372 miles, 34 mpg.
The only "mods" were tires at max sidewall pressure, adding a bottle of Seafoam to the tank (that engine sounded awful on cold mornings!), and driving technique.
The only technique I'm questioning whether I should continue is coasting down hills. It's the 3-speed AT; I don't kill the engine, so I'm essentially coasting at idle. My commute home every day is good for roughly three miles of coasting. I just don't know if it's okay for the tranny or driveaxle (and maybe it's not the coasting, but leaving gear and coming back into gear). I only have ever coasted in this car, and it's only been for the past week, but yesterday on the way home, I noticed an odd (and disconcerting) clunking in the car now--not just during coasting, but all the time (turning, over bumps, it doesn't matter).
Anyway, the EPA esimtate for this car is 27 mpg combined, so I thought for my first eco tank, 34 mpg was pretty cool. (And it's hard to retrain my driving habits; I was proud of myself for being able to keep my foot out of it!)

[elhigh]

One of the moderators will be along to do it more officially but until then, welcome!

34 in the unsophisticated Prizm is pretty good. The AT is definitely a stumbling block but you appear to be coping successfully.

Coasting in neutral is okay. I've done it for years and years in my Forester and previously in a Caravan. Goosing the throttle a bit before dropping back into D will help prevent the lurch on engagement. You might want to practice on some otherwise unoccupied road before getting really serious with it in traffic, however.

That model was also available with a 4-spd auto; if you're a dab hand with a wrench, have a thousand bucks lying around doing nothing and a free week to dedicate to a greasy project...

[user removed]

As long as the engine is running the primary pump in the transmission is providing lubrication. Two ears on the back of the torque converter slide into slots in the pump and drive the pump to produce pressure.

Is that the same as a Corolla? Sold under the GEO name.

Coasting in neutral with the engine idling means you are using about .2 gallons per hour of fuel, possibly lower. At 50 MPH that means you are getting 250 MPG coasting in neutral, since you could theoretically coast 250 miles and use 1 gallon of fuel. That can really improve your overall mileage quickly if you have good opportunities to coast without disrupting the flow of traffic around you.

Welcome to the Forum

regards
Mech

[mrmojo]

Thanks for the kind words and welcome.
I would love, love, love to swap the tranny out with either the 4-speed auto or 5-speed stick; I know that would be one of the biggest things I could do to help the FE in this car. And I hope that I can find one cheaper than a thousand bucks; I don't have that kind of cash lying about, and that would probably take years to break even with the increased fuel economy.
Yes, the Chevy Prizm is the same as the Toyota Corolla; in fact, the Haynes manual is titled, "Toyota Corolla & Geo/Chevrolet Prizm". It's the smallest car I've ever owned, and the first one I've tried to seriously drive with excellent fuel economy in mind. (One of the things I like about the car is that there's no timing belt; it's a timing chain, which me much more peace of mind.)
I'm just waiting for the rain to stop so I can get this car on the ramps and see where the clunking is coming from. I can feel it through the floorboards, and it feels like it's around the tranny, not the front wheels. (Or maybe it's my paranoia telling me that; I'll know soon enough; besides, it'stwo weeks old and should still be covered under warranty.)
Thanks again.

[user removed]

Transmission swaps on modern computer controlled cars can be very complicated. Work with your auto and maybe later think of selling the auto and buying a manual if you want to go that route.

regards
Mech

[Xist]

My old mechanic said that he never knew whether to order Toyota or Chevrolet parts for Prizms, which made me wonder about him. Was the body largely the same while the Prizm was Geo? I remember that Chevrolet made it look like the Malibu and then ceased production.

"Okay, Mr. Dealership Man, should I buy the Cavalier, Sunfire, or Prizm?"

[digital rules]

You are doing pretty darn good @ 34 MPG. The best I averaged with the 4 speed auto was 30-31 unless all highway. Almost bought a new 02 Prism, but opted for the 02 Corolla as it had the better manufacturer warranty at the time.

[elhigh]

That clunking might be a worn bushing in your suspension. If it does it only when the suspension moves - like you described - but not when you're in a steady state with nothing else going on like coasting on a straight stretch, then get 'er up on the stands and take a peek around. Or wheel on over to a suspension shop and while you're getting a good alignment, have 'em check that out too. They'll be equipped to set you straight toot sweet, and if your wheels are out of line that's some easy economy gains right there.

[cRiPpLe_rOoStEr]

I didn't even expect a '02 to still have that 3-speed transmission. Regarding neutral-coasting, some newer transmissions actually provide it automatically. The 4-speed one used in the Corolla and in many rebadged Opels sold in my country as a Chevy had this feature since '04 for the Opels, not so sure about the Corolla.

[mrmojo]

After two more tanks of petrol, I've averaged about 32-33 mpg, 33 mpg overall for the (i.e., my) lifetime of the car.
I haven't done any A/B/A testing, so all I can attribute the first tank getting 34 mpg is the Seafoam I added to the tank.
I had a clunking in my front end that happened near the end of that first tank, so I took it to the dealer. Turned out to be the sway bar link; replaced and voila! no more clunking. So I'm back to coasting whenever possible.
Money is very tight right now, so even saving $60 for the AutoGauge is taking awhile. I would love to change the oil, tranny, and differential fluid with synthetic, but that'll be a little bit.
Even more than that, I'd love to swap the tranny with a 4 speed AT, but that appears to also require an ECM swap, which elevates the cost to be prohibitive for the car. I'll probably just drive the car for a few years until I find another car that gets even better mileage and I can tweak more. (I'm not complaining, though; my last car averaged 23-24 mpg no matter how I drove it, so I'm getting 43% better than that beast!)
I love this forum!