Fuel consumption

[Claude]

Originally Posted by Thomas591

Gentlemen!
I am interested to find out what are the realistic figures when it comes to fuel consumption on the 8 Cyl cars. Please let me have your figures.

My 411 S5 400ci engine takes uses around 8 mpg / 27l/100 km.

Regards

Thomas Willig

In Bristol an Illustrated History (1990 First Edition) Oxley quotes on page 232 a range of 13-17 UK MPG (21.7 to 16.6 l/100)

and on page 282:
12 UK MPG (23 l/100) for full performance driving,
16 UK MPG (17 l/100) under 70 mph
and as much as
20 UK MPG (14 l/100) by some drivers

It's unclear if you are referring to US or UK MPG

27 l/100 = 10.47 UK MPG or 8.71 US MPG

I once visited some club members in the UK, and was in the passenger seat as my host's 411 was galloping along at insane speeds on very narrow roads. With such treatment, one would expect 27 l/100 due to lots of tromping on the accelerator after exiting each curve. Likewise if you are on the autobahn pressing the maximum speed of the car, such consumption may be expected.

But if you are driving gently so as to not spill the lady's G&T, as a Bristol gentlemen is expected to drive, then an engine tuner may need to have a look. I shifted my 411-S1 from a Carter carburettor to a Holley 670 Avenger custom tuned to my engine and it was transformative including better fuel mileage. My car came with the 383 engine, but somewhere along the line, the block was replaced with the 400 engine, but the 383 heads were retained.

It sounds like your fuel consumption is symptomatic of an improperly tuned engine or suffering from drag such as stuck brakes or a clogged exhaust pipe.

[Kevin H]

Originally Posted by Claude

In Bristol an Illustrated History (1990 First Edition) Oxley quotes on page 232 a range of 13-17 UK MPG (21.7 to 16.6 l/100)

and on page 282:
12 UK MPG (23 l/100) for full performance driving,
16 UK MPG (17 l/100) under 70 mph
and as much as
20 UK MPG (14 l/100) by some drivers

It's unclear if you are referring to US or UK MPG

I think it's safe to assume it is UK MPG.

However, Oxley is talking about the 360 engine, not the 400, which of course has a greater swept volume, and is an earlier generation of engine.
Can't imagine a 400 ever getting anywhere near 20mpg ...