zMax = snake oil

It's a waste of money. Ther Federal Trade Commission sued zMax dur to false and misleading advertising as well as unsubstantiated performance claims:

http://www.ftc.gov/opa/2001/02/zmax1.shtm

 

Thanks forthe info on the timing belt. That sounds fairly easy to check.

 

yup check those belts, loose belts are a good way to waste energy. even the accessory belts (outside the timing belt cover right in front of it) can waste when slipping.

things you can do if not already:
spark plugs
plug wires
distributor cap (the 1.5 has one doesnt it? 1.6 uses coilpacks)
try a synthetic motor oil, slight improvement for me
synthetic transmission fluid/oil
although expensive, replace oxygen sensors
overinflate tires slightly (check sidewall max pressure and stay below that)
toss your spare tire and get a can of the inflator/sealant stuff
learn how to 'pulse and glide' - very good in a manual

avoid the snake oils, additives of any sort, cleaners, even that seafoam. as an engine wears carbon and other deposits become part of oil seals. cleaning it out can cause leaks and even burning oil...

also avoid any fuel saving devices. they're all scams. if they worked the manufactures would have bought into them long ago.

most gas out there already has detergents in it to keep the injectors and such clean - thats why you rarely hear of dirty injectors causing trouble these days. want to clean it out good? buy a tank of premium from a good station like a shell and go out and flog the car. high rpms, heat and the higher detergents in premium gas will give the engine a good cleaning. after that go back to regular, theres no benifit for FE in premium unless the car was designed for it.

hope that helps.