Better mileage with turbo on or off?

[jmdr]

So, on my drive out to work I'm out on the highway for a good bit of it, generally driving between 100 and 110 km/h and I've noticed that I'm usually right on the line of where the turbo kicks in.

I'm wondering if anyone knows whether having the turbo kick in will increase of decrease overall fuel consumption if the speed is held nearly constant?

I know that driving a little slower generally gives better mileage, but thought maybe having the turbo on might increase the engine's efficiency??

Someone here must know a little bit of turbocharger theory? (certainly more than I do...)

cheers

[NiftyNev]

When the turbo light is on you are using more fuel. The turbo does not "kick in" as such as it's always spinning. The light indicates that the manifold pressure has increased to where the engine requires more fuel so the ECU does this by signalling the fuel pump to do so. That's the way I see it anyway.

Nev

[jmdr]

Thanks Nev, that's exactly the info I was looking for!

[cataclysm]

When the turbo light is on you are using more fuel. The turbo does not "kick in" as such as it's always spinning. The light indicates that the manifold pressure has increased to where the engine requires more fuel so the ECU does this by signalling the fuel pump to do so. That's the way I see it anyway.

Nev

Ditto that, with the proviso that on motorways, it's the load that uses fuel.
Tyre pressures make a difference, but air-resistance and lead-feet are the biggest contributers.