Not bad figures for a gasoline powered car. I'll be trying mine out on the highway, long distance, this weekend for pretty much the first time since I bought it. Been a while since I've driven a petrol car at highway speeds, hope the fuel consumption isn't too bad. Will probably stick at 80 as I want to make good time.

80. Does Wales have relaxed speed limits or was that a typo?

Nah I'm driving across England on the motorway, official limit is 70 I believe, however most drive at 80, and the Police allow 10% + 2 Mph (78) anyway.

I'm a great believer in the 10% as well.

So what was the calculated mpg on the slower return trip? I think you said something like 39.2 on the going leg but didn't go back to double check.

The return trip wasn't necessarily slower, I just started out with the slower portion first, as opposed to the slower portion last on the toward trip. About a third into the drive, I topped off at 219 miles it was calculated at 38.7 MPG while the OBC read 40.2, according to the pic I snapped that I just looked at. I'm still on the second tank used on the trip as we speak. This trip overall was slightly faster than my toward trip because I was keeping up with my brother and the first tank definitely involved more hilly Southern Interstates, as opposed to more flat Illinois Interstates more north so it evens out.

Decided against the motorway route, instead I stuck to rural roads. Horrible journey which took 4.5 hours, usually less than 3.5. Lots of slow tourists, caravans, holiday traffic and a town carnival.

As you can see the stop start feature saved wasted fuel from idling in traffic for a total of 26 minutes and 26 seconds. A worthy feature in any car. Actual MPG would be about 42 UK V's the 45.5 displayed.

Ok quick question rather than start a new topic. Occasionally, perhaps about 8 times since I had my car, upon start up in the morning, it will go into a fast/loud idle. The symptoms are: very loud exhaust, as if I fitted a straight through system, high rpm about 1500, and cute backfires if you give the engine even a small rev. I also noticed the dump valve staying open longer resulting in a long hiss after revving.

So what causes this? And is there a reason to be concerned? Is it common with high performance engines? Seems to be no particular factors that affect when it occurs, outside temperature, fuel type, what I had for breakfast blah blah.

I would be inclined to discuss it with the dealership from whom you bought the vehicle.

I would, but need to know if it's considered normal first. I've had cars go into fast/cold idle before, but it's never been as obvious or apparent as in this one.