Best MPG for cruising @ around 100-120mph

[Ry_B]

Hello all.

Quick question. What car will give the best (or good) MPG for cruising at around 120mph?

My friend does a lot of late night shift driving and she was wondering what would be best suited as her 330i currently is drinking like a fish. I've suggested something with a big diesel engine should hopefully get high 20's, but have no experience in economical cars.

Thanks

[chard]

Drive slower, doubling the speed requires 7x the power

[SonicHedgeHog]

Are you taking the p1ss? She drives at 120mph and is worried about fuel economy? Stupid cow.

[H_Kan]

Ry_B said:

Hello all.

Quick question. What car will give the best (or good) MPG for cruising at around 120mph?

My friend does a lot of late night shift driving and she was wondering what would be best suited as her 330i currently is drinking like a fish. I've suggested something with a big diesel engine should hopefully get high 20's, but have no experience in economical cars.

Thanks

Regularly doing those speeds in the UK is likely to result in a ban sooner rather then later.

Though you are right, larger engined derv barges are going to be the best bet here.

[bazking69]

I do hope she works in Germany not this country.

[dcb]

chard said:

Drive slower, doubling the speed requires 7x the power

You are on the wrong website - this is pistonheads.com,
speed matters.

Anyway, the original poster asked about mpg, not power.

To cruise efficiently around 100-120 mph, you'd need a
medium diesel. Something like a BMW 325D would do it.

I'd recommend have a search on the various German car
magazine websites. Auto und Motor Sport springs to mind,
but there are many others.

Some German will have measured the litres per 100km at 200 kmh
in some group test somewhere.

[anonymous-user]

I would say a larger engined diesel; 325d/330d

[Matt UK]

I wouldn't be surprised if big US V8s play this game well with there high torque / gearing.

[Trommel]

anonymous said:

[redacted]

There are plenty of safe opportunities for 100+ cruising.

How small-minded are you?

[Jonny_693]

Trommel said:

There are plenty of safe opportunities for 100+ cruising.

How small-minded are you?

There are, but I doubt plod will see it that way.

[balls-out]

At that speed I think she'll struggle to get anything that doesn't use a lot of fuel. The law of physics dictate that it'll need a lot of power to maintain.

[SonicHedgeHog]

anonymous said:

[redacted]

This isn't about the rights and wrongs of driving at high speeds. Someone who drives at 120mph and complains about poor fuel economy is clearly an idiot.

[homerjay]

the OP is on a massive fishing trip surely???

[davy9449]

I find this post one of the most bizarre things I have ever read.

To add to the post above, there are some bloody idiots out there. Not to say I haven't experimented but this is just stupid.

[Matt UK]

Why jump to conclusion - has the OP not stated that his friend lives in Germany?

[dcb]

balls-out said:

At that speed I think she'll struggle to get anything that doesn't use a lot of fuel. The law of physics dictate that it'll need a lot of power to maintain.

I think you are showing your ignorance there.

Power isn't the same as mpg and acceleration isn't the same as velocity.

In practical terms, I find cruising at 100-120 mph
costs only 1 or so mpg over cruising at 70-90 mph, so it's
entirely reasonable to do so, where permitted.

[Petrolhead_Rich]

20MPG is about your lot for cruising at those speeds, I get 18-19MPG between 100-120, then it drops to 17MPG for 120-130, down to 15MPG for 130-140, and around 14mpg for 140-160 (can only touch 160 going downhill though), on level it tops out around the 153mph mark

If working late, 120mph is nothing, especially in Germany.

[redgriff500]

I used to go back to my work placement every Sunday at around midnight and sat at 99 on the M5 but once on the M54 130.

I did this for a year, completely safely, no kittens were hurt.

High gearing and good aerodynamics are what you need.

I had nieither but I did have a 2ltr turbo, a job and no kids / mortgage

[Condi]

dcb said:

balls-out said:

At that speed I think she'll struggle to get anything that doesn't use a lot of fuel. The law of physics dictate that it'll need a lot of power to maintain.

I think you are showing your ignorance there.

Power isn't the same as mpg and acceleration isn't the same as velocity.

In practical terms, I find cruising at 100-120 mph
costs only 1 or so mpg over cruising at 70-90 mph, so it's
entirely reasonable to do so, where permitted.

I doubt that for a 50% increase in speed your car uses a 5% increase in energy. If you can do this, bottle it and make a fortune.

[busta]

Something slippery would be good. How about an Elise with longer gears?

I probably get around 25mpg* at 120 in my 106, but at 6,500rpm it's a bit noisy and you feel very vulnerable!

* never done a 120mph run and measured it but I get, at worst, 25mpg on a track day. That is full throttle, redline in each gear nearly all the time but with much lower average speed, so I don't imagine it'd be any less than that.