Message from Dervman

180, and 70mph?

"A speedo over-reads by design, but I think you'll find the mileometer part of it is far more accurate - what the speedo indicates, and what the mileometer clocks up, isn't like for like."

IME they've always been optimistic with regards to how far you've actually travelled, but I'll take your word for it.

"Yes, all these wicked car manufacturers... haul them up in court, because their claims for MPG must be vastly inaccurate as well, given I've bothered to work out the MPG achieved on most of my cars, at lower speeds, as well as the higher ones.

Using your logic, at the lower speeds, they've grossly misquoted achieveable figures, because using your methods, I'd be calculating I was getting that many less miles to the gallon than the calculations showed..."

LOL!

High average speed motorway stuff is more like "constant 100" than the "extra-urban cycle scaled up to 100mph average" which is why they'll never match up. Old constant 56mph numbers probably would scalebetter.

"You've made a lot of, what I believe to be inaccurate assumptions I'm afraid "

I'm not disagreeing with you mate - you've stated that a Golf will do nearly 50mpg at an average of nearly 90mph and I ain't disputing that; merely using a couple of your numbers to attempt to explain to

50mpg@100mph average astravanman why he's spouting bollocks... ;-)

Subsequent posts reveal astravanman wasn't entirely serious anyway and that the methods used to determine: distance covered, fuel used, and average speed are a complete joke. From the description of the journey it sounds like 55-60mpg at an average of ~75mph, and unless there was

1hr+ at 135+mph indicated theres no way it'll have averaged 100mph between fillups. Fuel use won't scale the way he'd like either. The 50mpg@100mphaverage case is clsoed - it didn't happen and won't happen again if you actually measure anything properly astravanman.

Hehe - something which I freely admitted!

You're probably right there, but based on JackH's 48mpg @ nearly 90mph average in his Golf, I'd reckon that an Ibiza with the same engine, and less weight, would happily do at least 45mpg at a constant 100mph.

"but based on JackH's 48mpg @ nearly 90mph average in his Golf, I'd reckon that an Ibiza with the same engine, and less weight, would happily do at least 45mpg at a constant 100mph"

Weight difference irrelevant at those cruise speeds. 45mpg wildly optimistic still IMO, but by all means try...

Over 400 miles? :)

Well, we were touring to our next destinations...