(1) Last Saturday on 29th May, when I had my oil and filter change I checked the oddometer before the oil change, and it read 1440 miles.
However, the service receipt said I had done 1140 miles! That is a 300 mile difference! However, I did not think too much about this as maybe I had made a mistake or they had. Easily done.
(2) This Saturday on the 5th June, when I had the gearbox additive put in, the oddometer read 1150 miles as did the receipt. Alarm bells started ringing!
Between the 2 Saturdays I have covered around 18 miles per day which makes it a total of 133 miles. So the oddometer should read 1273 miles! Well it does not and says I have covered 10 miles in a week even though I have driven the car every day to and from work!
My car seems to be clocking itself in a most outrageous manner by approx 423 miles!

Any ideas please?