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post #49 of (permalink) Old 14th May 2006
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The plot thickens. I did a run into work, still on the BP diesel and only managed my usual 42'ish. Then filled up with Shell Diesel Plus (or whatever it's called) and managed a fairly disappointing 47 on a relaxed run to Blackpool. So I reset the trip on the A55, and did the steady speed run for a few miles, and once again I was getting 50+.

So maybe it's not the fuel, just that even moderate changes in speed (even without braking) can have a seriously detrimental effect to fuel economy. I've always looked at braking as being a waste of fuel (you've used fuel to build up inertia, and are now throwing it away as heat through the brakes) but would have thought that gentle acceleration and deceleration (without braking) wouldn't have that much of an adverse effect on economy.

Obviously I was wrong.
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