6.9 fuel consumption

[6.9forever]

I'd be very interested in fuel consumption data amongst the 6.9 community...

My AUS-delivered model delivers 20-21 litres/100km (about 13.5mpg) when driven sparingly in the Sydney metro area (not much peak hour or bumper-to-bumper).

I am a bit discouraged by this even though it is a huge-cube motor...I suppose I was hoping for north of 15mpg but without resorting to a trip I haven't managed that yet (and my tyres are pumped up and engine in reasonable tune).

I am aware the AUS ADR27A motors are not quite what the higher-compression Euro motors are...

Any comments?

 

[6.9forever]

...and I should add that I always use 95 or 98 premium unleaded.

 

[B13]

I get 400km/tank before the low fuel light comes on. Thats bumper-to-bumper melbourne traffic every day.

On the occastions I go for a decent highway drive at a constant 100-110km/h I get 450km/tank. But I've not really had the chance to do a constant 110km/h interstate run to see if I can get that figure up to 550km/tank or more (probably not likely but I can hope).

Mine's got the 8.0:1 Aus engine, air pump disconnected, cold start injector disconnected, ignition advanced about 0 degrees, new timing chain and rails, k&n filter, uses 98 RON petrol, which I think all help a little bit in their own way...

On the downside I have wide 245-series tyres, lots of rubber contacting the road.

Ian.

 

[Styria]

Hi guys, as a rule of thumb, I would estimate that the difference in fuel consumption between the high and low compression engines would be in the region of a constant three miles to the gallon.

My 'Gleaming Beauty' gets to about 510-540 kilometers before the reserve light comes on - conditions are light traffic, and semi country running to my storage shed at Glenorie. No. I need to correct these figures. For every 50 litres of petrol, I go very, very close to about 300 kilometers but, in days gone by when the engine was somewhat healthier than right now, one country trip to to Orange via Yass returned 20.6 miles per gallon cruising at a minimum of 110 to 140 once I left the highway. That was an exceptional trip.

On an Economy run about four years ago, the consumption was 22.5 mpg. When compared with an R129 500SL, I just shaded that car on actual consumption, but got done on ton miles per gallon. They weigh more than 6.9's, believe it or not. Regards Styria

 

[WGB]

I don't think the high compressioned ones are much different.

To put it into perspective a 450 motor is only about one MPG better.

Both are almost lineball to two of the Petrol Toyota Landcruisers I have owned (The third fitted with an LPG kit was a lot worse when run on Petrol).

As a counterpoint Wheels magazine road test of the early 80's Five litre Holden Statesman was 13.5 mpg as well.

Bill

 

[Andrew280SEL]

I don't own a 6.9 obviously, but from what I'm reading, it would seem that these big 70's motors (in good tune) aren't really that bad on fuel, at least for their day.

 

[Styria]

Hi Andrew280SEL, that is precisely my point as well. The difference between starting from 280 up to 6.9 is not all that great, and at various times, I have actually shaded smaller engined 116's on Economy runs.

Even on those, I prefer to drive at no less than 90km/hr on the open roads just to be as close as possible to maximum torque - I have found very little difference consumption wise between 90 and 120k.'s an hour. Regards Styria

 

[BenzBoy]

Before the 450 went south, it gave about the same consumption figures as the 6.8 litre SS motor - that is about 14 to 16 litres poer 100 kilomteres. I estimate that is roughly the equivalent of what you are saying in mpg. It does take a certain mount of power to move the size and weight of the vehicle. I have never noticed much difference between city and country driving - although after a few blasts down the freeway, the motor cleans out a little and runs more smoothly.
If consumption of petrol was a worry to me I would move to a smaller car. Maybe a Lotus? I must go to Rick Damelians for a test drive before I commit myself to an older Bently, as it could be that a bice 2nd hand Lotus outs sa real grin on my face. Any thoughts on a Lotus?
benzboy

 

[Styria]

Before the 450 went south, it gave about the same consumption figures as the 6.8 litre SS motor - that is about 14 to 16 litres poer 100 kilomteres. I estimate that is roughly the equivalent of what you are saying in mpg. It does take a certain mount of power to move the size and weight of the vehicle. I have never noticed much difference between city and country driving - although after a few blasts down the freeway, the motor cleans out a little and runs more smoothly.
If consumption of petrol was a worry to me I would move to a smaller car. Maybe a Lotus? I must go to Rick Damelians for a test drive before I commit myself to an older Bently, as it could be that a bice 2nd hand Lotus outs sa real grin on my face. Any thoughts on a Lotus?
benzboy

Benz Boy, eleven years later the answer to a Lotus would not be favourable. It's an old thread, brings back memories and still holds interest to some degree. Regards Styria