like it says: if my speedo is showing more than i'm actually going, would i have less miles on the car than the odometer shows?

sorry if its not exactly second gen specific, just kind of a general question i've been wondering thanks.

 

Yes and no. You've travelled less than it shows, but the wheel bearings, driveline and such will all essentially have the higher milage, since they turned more times per mile, so wore like they went farther.

 

^^Yeah, that's true if you get smaller wheels or something. However,if your speedo is broken then your car's wear and tear will be less than ti shows as well.

 

Damn, and I thought I was getting good mpg. My speedo reads 5mph faster then what im actually going.

 

yes...

 

my speedos off too. any way to fix it?

 

Sure, there are speedo repair/calibration shops still around (although with the trend to electronic units they may die a slow, wasting death...).

Basically, they put your car on rollers (like a dyno or etest) and run the car up to a known speed and find the gauge's discrepancy.
Then they build a custom gearbox that gets interposed between the speedo and the cable which corrects the error.

I had this done when I swapped the transmission, diff and wheels on my 240Z- cost about $80.

There was a lot of room behind the Z's dash though, the Mazda is much tighter so I'm not sure how that would work.

You can find such a shop by checking with your local State Police...their speedos are calibrated/certified regularly.

 

It's not uncommon for the speedo to be fast, in fact if you look at the specs in the FSM it lists the allowable error and it gets pretty big when you start getting fast, and the spec is that it'll list fast, or equal, never low (don't want the drivers getting unexpected tickets).

You can change the speedo gear in the tranny to compensate, but there's probably only 2 or 3 available (3.9, 4.1, 4.3).