Hi Peoples
My speedo reads 5 MPH out ,so when the speedo says 30 mph I am doing 35mph which is ok as it has been like that for years, but now I have an odometer that works so I want to work out how many miles I have covered, So if the speedo is reading lower then the odometer must be reading less aswell .
Hopefully I explain it better this time LOLOL

So does anyone know how to work it out.

Thanks

Marc

[ Edited on 24-7-06 by Midlife crisis ]

fill up the tank... run it down to at least a quarter then fill up the tank again... take note of the odometer reading both times when you fill up... take note of the litres you put in the second time... then you can work out how far you went on how many litres.. .simple maths calcs and you can get litres per 100k's etc...

it is recommended that you fill up using the same petrol pump and holding the pump nozzle in the same position in the filler neck and let it cut out at the first click.
if you do this it is assumed you have taken out a few variables which will give you slight errors in the calculations...
having said that you can do these calcs over 3 or 4 tanks and average it out so you get a better idea of what you are getting per 100k's.
just depends whether you want a city driving value or a highway value or a combination etc..

Thanks blutopless2

I must not have explained my self correctly ,I am not try to work out k's per litre, I want to work out the correct miles I have travelled seeing that my speedo reads 5 mph slower that I am going, Speedo reads 30mph but I am doing 35mph.So my odometer must be reading less miles covered.

I will edit my first post as well

Thanks

Marc

You need to know if your odometer is accurate, too. Different tyres sizes will upset its accuracy; soundlike smaller wheels on yours are making it read 'fast'.

Use the 'speedo test length next 5km' signposted on many freeways or follow a mate's known accurate late-model car for 10km or so and figure out what your percentage error is

think you can also use a GPS to check speedo and odometer accuracy.

Kool

Yeah I have 225/75/15 on the front (BAJA).

Thats a good Idea My son has a new Swift so will get him to do it .

Thanks for the idea,

Marc

if it is an even 5mph out all the way up the scale then base it on your averags speed (say 60kph, which is about 36?mph) for every 41 miles registered on your odo i would think that 36 would be actual, so out of every 100miles, about 88 should be the actual. thats a pretty rough way of doing it though.

The odo and speedo run off different mechanisms (at least mine do). The speedo runs off a magnetic disc, while the odo is directly driven by gears. While different size wheel/tyre combos will effect both readings, you cannot necessarily directly relate errors in the speedo to errors in the odo. As others have suggetsed, the best way of checking would be with a GPS.

Yeah the GPS is the first thing I would do. I have checked mine out in the beetle and it spot on....my 2yr old Honda Accord is out by 3km at 60k. Goes to show that a 36yr old German instrument is better than a new jap one.