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View Full Version : Onboard computer mpg - hugely over-reading



jdl_1967
26th April 2010, 06:15 AM
My MCS on board computer seems to make up my average mpg.

I reset my on board reading prior to doing a 200 mile motorway journey anf fully filled the tank. I averaged 70mph with cruise and the computer said I'd averaged 39.2mpg. I was over the moon until I refilled and manually worked out my fuel economy, it was only 31mpg, how can my computer be this far out? it normally over estimates by 1-2mpg, but never 8mpg.

I've looked into reseting the fuel computer, but I don't have option 20 on the test sequence.

Any thoughts greatly appreciated.

John.