Which uses less fuel?

Ok, someone told me that when slowing down on a slipway off a motorway or similar change down early and engine brake as it uses less fuel than clutch in and brake. what are peoples opinions on this, ture or false.

NB, this was in a car but i guess it will apply for bikes as well

[Viney]

Clutch in and use the brakes only. The engine will use less fuel at tickover in theory

Would have thought that any difference would be measured by the thimbleful.

Either way, engine braking probably leaves you in more control, clutch in and coasting with application of the brakes doesn't sound particularly settled.

[Biker Biggles]

I reckon engine braking but not quite as you describe it.What really uses less fuel is getting off the throttle earlier and hence using less brake.Brake is simply converting moving energy(which you have paid for to get up to speed)into heat dissipated at the brake disc.Get off the throttle sooner and you have used less fuel before you need to slow down.

[jambo]

Depends on the fuelling system. Top Gear took a V8 diesel Audi to Edinburgh and back on a tank of fuel a couple of years back. With the modern FI in that if you coasted with your foot off the gas the FI put no fuel into the engine at all, as the engine braking was keeping it turning. A similar system was much criticised on Yamaha's FZ1 when it came out as it led to a hesitation as you went from negative to positive throttle while cornering.

Carbs, of course will always add a little fuel as long as the engine is turning, but using smooth, gentle throttle in the correct gear and not building up speed that you then need to scrub off helps fuel economy.

If all else fails, fit a Sid Squid, annoyingly this makes more difference to fuel economy than anything else I've tried.

Jambo

[the_lone_wolf]

Originally Posted by jambo

With the modern FI in that if you coasted with your foot off the gas the FI put no fuel into the engine at all, as the engine braking was keeping it turning. A similar system was much criticised on Yamaha's FZ1 when it came out as it led to a hesitation as you went from negative to positive throttle while cornering.

in any car from the past decade this is probably the case, cars don't have the lurching problem because the inertia of the vehicle dampens the movement, they also have had more stringent emissions regs that bikes are only getting now so it's almost certainly going to be more fuel efficient to leave the engine in gear and slow down using engine braking and the brakes as required

[Stu]

I'll see your Sid Squid and raise you 55mpg

Originally Posted by Viney

Clutch in and use the brakes only. The engine will use less fuel at tickover in theory

Yep, I think the same... but your just end up spending your savings on pads.

[yorkie_chris]

Curvy carbs have TES which dumps fuel in on the overrun. But I don't like coasting as then you're going to end up in the wrong gear when you need some power. Engine braking at about 5krpm means it's easy to get out of someones way when they do something silly. Try that when you're at 30mph with clutch in and still in 5th gear!

[Stu]

OK, now that's answered that engine braking uses no fuel so is the perfect economical way to slow down. What is more fuel efficient when you don't want to slow down? Engine braking using no fuel or clutch in & coasting far longer/faster?