It just so happened that my hybrid Yaris was bought at the same time as my son was attempting to climb all Scotland 282 Munros (mountains over 3,000 feet or 914 metres) in a single season. Consequentially, I've done a lot of driving around in support of his endeavour and this has given me a lot of experience with the car. Overall, I'm very much enjoying the car as I get to understand its characteristics. With all these miles around the country's Highlands, I tend to keep my fuel consumption between 65 and 70 miles per gallon.
Then we left for a three-week spell to cover his final push to the end of the challenge. During that time, I felt a change in the car's performance. Gradually, over the first week or so, the car felt a little more sluggish, as if something was holding it back. It seemed to need a little more power from the engine to get it going and was less keen to drop into fully electric mode at slow speeds. As a result, the battery discharged less often and, for the first time, I saw the battery display show it as being full.
The consumption figures reflected this change. Throughout the three weeks up north, the consumption stayed solidly around the 60mpg mark. I became increasingly certain that something within the car had changed. I was convinced that my driving techniques were very similar to what they had been before the trip, when I had been following my son along roads further south. The sense that something was holding the car back was a disappointment and I began to think of how I would approach the subject with the mechanics. "Hi, I think I've detected a 10 per cent drop in my car's performance. Can you run a battery of tests to confirm this?"
There are a lot of possible sources of increased friction and the obvious culprit was a soft tyre so I made a point of checking them. Nope. Perhaps one of the brakes was the problem but how do I check that? That or any problem with the car's traction system would have to await specialist work when I return. What made it worse for me was that the early part of the tip was during a heatwave when the atmospheric density was lower and therefore so was the drag, something that should have countered my perceived problem.
Then we made the long trip back.
Soon we had left the winding, undulating single-track roads of the far north and were back on 2-lane roads with a higher average speed. As I emptied the tank, I watched the mpg meter slowly increment to a better figure. Then after a top-up at Pitlochry, I found it easy to maintain 55mph at about 70 miles per gallon - that was as good as I was getting before the trip.
Since then, the car's performance has been exactly as I was used to prior to the trip - the meter is currently sitting at 71mpg as I tootle around town. My current hypothesis invokes a mixture of the stop-start driving that is constant feature of the single-track road with its passing places, the very steep undulating nature of the landscape and its roads, and a notion that the road surface preferred up north is maybe different to cope with the harsher winters and the need to provide more grip. I don't know, but I'm sure happy to see that the car is fine.
