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MPG Van Computer

seppala

New Member
Joined
Oct 13, 2019
Messages
2
Location
HX30UQ
Car
Mercedes Citan 109 1.5 CDI Long
Driving my used Citan Van 2014 plate 1.5 DCI 90 BHP

Always believe the best speed achieve best fuel economy was 60-65mpg

Driving over 30-35 miles i had 48.5mpg the figure moved very slow from 48.2 steady 60-65mph

On the drive back i increased the speed 70-75 mpg and the van calculated 53mpg

I know the gains are not much but surely i should have been getting better fuel economy at 60-65.
 
It's possible the engine is operating more efficiently at higher revs i.e it's specific fuel consumption for unit power produced is better at 70-75 MPH.

But there are other possible variables such as a head wind on the way vs tail wind on the way back. I do a regular run from Manchester across the M62 and up to York. The journey there consistently achieves better MPG than the return trip and by some margin. I'm convinced that is almost entirely because the prevailing wind is from the west.
 
It's possible the engine is operating more efficiently at higher revs i.e it's specific fuel consumption for unit power produced is better at 70-75 MPH.

But there are other possible variables such as a head wind on the way vs tail wind on the way back. I do a regular run from Manchester across the M62 and up to York. The journey there consistently achieves better MPG than the return trip and by some margin. I'm convinced that is almost entirely because the prevailing wind is from the west.

I tend to agree. A regular journeys almost 200 miles due east to Norfolk very often return a huge 10% variation. Typically 42mpg east and 38mpg west.
Still not too bad for a 3 litre 'town hall' shaped 4x4 SUV. I don't think the 450' difference in altitude is massive factor after 400 miles!
 

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