Mph, mpg, milometer reading??

[Fenman]

My last two vehicles have had digital dashboards.
I love that I can easily see the exact speed and can change from miles to km with the flick of a switch.
Since having them I have noticed that my speed reading when I pass one of those green and red warning things is always 2 or 3 mph or kph different. If the warning thing says 40mph my speedo will read 37mph.
I always understood that speedos had read 2 or 3 miles high since the year dot to discourage speeding but the old needle dials didn't really allow you to see accurately what the speedo said.
My query concerns that difference.
Does this difference apply to the miles registered on my milometer? Or does a reading of 40,000 miles really equate to 37,000 miles. Likewise, if I fill up with fuel and divide the litreage by the clocked miles on my dash am I out by a few miles per gallon?
Opinions would be welcome.

 

[Minxy]

I think the number of miles will be correct, it's just that when they put the needle on the speedo they moved it to the right slightly so it over-reads the speed!

 

[gus-lopez]

Since having them I have noticed that my speed reading when I pass one of those green and red warning things is always 2 or 3 mph or kph different. If the warning thing says 40mph my speedo will read 37mph.

If you are talking about the "speed warning "flashing signs in the UK,then ignore them .They do NOT give the correct speed They are set to depress your speed even more by over stating the speed. Whenever I see one I always check against the 2 gps's & if it is flashing 40mph the gps's will be showing about 36/7.
All this does is make people go even slower so they are barely exceeding 30 mph!!

 

[suavecarve]

Bigger wheels ?

 

[Chockswahay]

https://en.wikipedia.org/wiki/Speedometer

https://en.wikipedia.org/wiki/Odometer

https://www.autoexpress.co.uk/car-n...erances-revealed-is-your-cars-speedo-accurate


Yup, you will actually have travelled less miles that your odometer indicates

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[rosalan]

... but hopefully avoided crossing the fine line between speeding fines and having a fairly clean bill of health

 

[pappajohn]

I always understood that speedos had read 2 or 3 miles high since the year dot to discourage spe

The law, and construction and use regulations, allows a speedometer to show a speed FASTER than true speed to a maximum of 10%... It can be anywhere in that 10% error.
A speedometer CANNOT BY LAW show a speed SLOWER than the true speed.

The roadside sign will be set higher than true speed to encourage you to slow down even though you may be below the signposted limit.

 

[berni109]

https://www.motorhomefun.co.uk/forum/threads/which-do-i-believe.196116/

 

[Fenman]

https://www.motorhomefun.co.uk/forum/threads/which-do-i-believe.196116/

Thanks. Hadn't seen that thread or I wouldn't have asked the question.

 

[Allanm]

There’s a good chance your total mileage will be out too. I’ve never really taken much notice of my total mileage or had anything to compare it to, ( or any need) but earlier this year I hired a large Renault van in France to help my sister move house. I estimated my mileage ( kilometerage?) was going to be about 2000 km. ( my house to my sisters, 900 km each way, and about 100 km running around while I was there with a few km in hand)
I noticed, as usual, the speedometer read high compared to my sat nav.
When I got home and handed the van back I was surprised that it said I had only covered just over 1600 km, around 300km less than I had actually travelled.
Just shows how totally inaccurate the speedo was on a brand new Renault van.

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[Chockswahay]

When I got home and handed the van back I was surprised that it said I had only covered just over 1600 km, around 300km less than I had actually travelled.

Well if you pay by the mile/kilometre then that would be a good thing surely

 

[Pausim]

I think the number of miles will be correct, it's just that when they put the needle on the speedo they moved it to the right slightly so it over-reads the speed!

I agree. I have two vehicles with both analogue and digital speed readings. The analogue speedos always reach the the limit a bit before the digital one and the digital readings are generally in line with gps ones.

 

[Allanm]

Well if you pay by the mile/kilometre then that would be a good thing surely

Trouble is, you have to give them a figure and you pay upfront