Geo XFI Cam or Tranny swap.
 

ok so switching the transmission out of my regular 5 speed metro to an xfi tranny is possible, but is there any thing else I would have to swap in order for the car to run right? Is it possible to switch the cam to an xfi cam,without any other mods and the car run right? How do I identify an official xfi transmision at the junk yard? What will the increase in gas milage be with just a cam swap?

What year is your Metro?

It is a 1991

The XFI had all black bumpers, but you'd have to count the turns in and out to be sure of a tranny model, AFAIK. The 8-valve had the same ratio, which may be easier to find.

Base model Metros had black bumpers too. Only the LSi had the body-colored bumpers.

And the 8-valve 89-94 Swift tranny is not the same as the XFi tranny. It's a taller final drive than the XFi. 3.52 for the 8-valve Swift vs 3.79 for the XFi. Neither are easy to find, use the 3.52 if you can get it. The 1995+ Metro and Swift with the 4-cyl have the same final drive as the XFi, and those are easy to find.

Count the ring gear teeth if you want to be accurate. XFi ratio tranny will have 72 teeth. And the super-tall 3.52 Swift tranny will have 74 teeth on the ring gear. Remove the triangular metal plate to count the teeth.

I don't know anyone who's quantified the efficiency gain of the XFi cam - it's too hard to do in any kind of controlled fashion outside of using a dyno).

If I had to guess though, it might be worth a couple of percent improvement.

Going to the 3.52 (tallest available) final drive was worth about a 5% gain for me.

cheap improvements to 2000 Metro 4 cyl
 

So, Is it safe to say ,that driving habits have the greatest influence on making my 2000Metro lsi 4 cyl. get the best MPG ?Any recommendations about lubricants or fuel? I'm new to this game but OCD when jacked up on a new idea. Thanks in advance

Yes.

If you want to achieve the same with aerodynamic and other mods, you'd have to go all the way as basjoos did with his Aerocivic - Honda Civic modifications for maximum gas mileage - aerocivic.com ;)

If you combine both, the results can be really stunning.

Driving habits are free, so they automatically return the biggest bang for your buck :)

They're usually where the largest initial gains come for people new to the efficiency game.

A few years back, I tried to quantify the gains from driving technique vs. mods. At the time I came up with 38% from driving, 28% from mods (the ones I had tried up to that point, anyway). 2006 retrospective (there's more where that came from) - MetroMPG.com