3.9 v8 fuel economy

**Dougal** · 29th July 2013, 02:52 PM

Originally Posted by 98discovery

One thing which will play havoc with fuel economy,if thats the correct term, is the thermostat.I replaced it 2 months ago after finding that it was stuck fully open and it has made a huge difference to economy and idle.As I only drive 15km each way to work the engine was not warming up and still running rich when I arrived.
With the new 88deg thermostat it warms up very quickly with the added bonus of a heater that warms up the car. Its an easy one to overlook with the one temperature suits all gauge that never seems to change.Looking back I suspect that mine failed over a period of time rather than overnight.

Yes a thermostat change has improved my rrc 3.9 v8 from 4km/l to 5.

But at least now the heater works.

Mine however has some extra issues. Which I think now are either fuel filter or cam. I'll change the filter next. It has to be cheaper.

There is a fuel economy benefit with some petrol engines from a warm air intake. This is because warmer air is less dense and you run the throttle open more to reduce pumping losses.
However, it reduces power and the net result depends on the tradeoff between optimum ignition timing and pumping losses. If you have to retard the spark more to run warmer air, then you may lose more in efficiency than you lose in throttling loss.

I was going to try this on my last petrol car, but just sold the car instead. No such option exists for the V8 rangie.

**101RRS** · 29th July 2013, 03:35 PM

In a squillion threads people keep banging on about the poor fuel consumption of V8 Discos and RR however given that we are looking at a 2 tonne 4wd it is actually pretty good.

Compare it to the petrol competition of the time - Landcruisers in all its variations, Patrols etc and you see how good the Rover V8 is in comparison. My jag is only pulling around 1500kg and I average 14mpg so when put into context the Rover V8 is not too bad - issue is people compare it to new CRD high speed diesels and the old V8 is never going to compete.

Garry

**tony66_au** · 3rd August 2013, 03:05 PM

Im still chuckling at some of the "Suggestions".....

I see this a bit on the old Mercedes forums too, What economy can I expect from my 74 450SEL etc etc.

I don't have a Disco yet but the wife has placed an order with the Transport Qmaster (Me) so I shall own one soonish I suspect.

My ethos on this stuff is this, Keep the car well fettled using quality parts, filters and fluids... Don't go loading the thing up as if you are about to head down the Tanami track and keep your tyre pressures up and equal and she will be reasonable to run.
I rather like Caltex fuels for a little extra mileage but fuels are a local thing so YMMV.

Drive her nice, dont load up the electrical system with DoofDoosh, car melting spotties etc and your economy will be ok.

Some fine tuning of the air fuel system may be in order as well but that's all maintenance.

What you will get is a fairly unique driving experience compared to any other 4wd and of course you'd expect to pay a little more for that.

Enjoy!

**laurie02** · 4th August 2013, 10:39 PM

EPO....works for push bikes...but don't tell anyone

**Dougal** · 5th August 2013, 08:12 AM

Originally Posted by tony66_au

My ethos on this stuff is this, Keep the car well fettled using quality parts, filters and fluids... Don't go loading the thing up as if you are about to head down the Tanami track and keep your tyre pressures up and equal and she will be reasonable to run.
I rather like Caltex fuels for a little extra mileage but fuels are a local thing so YMMV.

Reasonable is a very subjective thing. I'll let you know the first time my v8 rangie uses less than twice my diesel rangie.

**tony66_au** · 5th August 2013, 08:23 AM

Originally Posted by Dougal

Reasonable is a very subjective thing. I'll let you know the first time my v8 rangie uses less than twice my diesel rangie.

Anndra Ridh · 9th August 2013, 09:40 AM

Originally Posted by laurie02

EPO....works for push bikes...but don't tell anyone

As an additive in the tank

Anndra Ridh · 9th August 2013, 10:00 AM

I am getting on average 20l/100km. I am happy with this given that, yes, it weighs 2200kg, is basically a house on a chassis and has modest H/T tyres fitted. I tend to burble (doesn't it but!) along the highway at 90km/h and ride my push bike more when I am in town. Mind you, it is a small town.

I consider myself a conservationist Greenie, so the irony of now owning a V8 in these political and environmentally challenging days is not lost on me. Like all things in that range of debates, moderation and appropriateness of purpose is how I manage to delude myself that it's ok

**101RRS** · 9th August 2013, 11:11 AM

Originally Posted by Anndra Ridh

I am getting on average 20l/100km.

That is too high - you need your car looked at.

Garry

Anndra Ridh · 12th August 2013, 09:26 PM

Originally Posted by garrycol

That is too high - you need your car looked at.

Garry

Cheers, Garry. Have it booked in to see Justin Cooper as it has been running too rich and small timing/idle issues

edit: What do you expect it should be returning?

Thread: 3.9 v8 fuel economy

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