I am confused - I've just been down to Devon, did 300 miles in a day, twice, I was trying to find the best place to sit for best MPG, strangely enough I was getting 51.2MPG at 72MPH, around 3.5k revs, but only about 48-49 at 62ish, 3000 revs? How does this work out?

Also I found, driving it slightly harder, not just been a granny on the revs and going above 3k revs, returned better fuel economy too?

Any explanation for this? I'm confused.

Anyway, on the positive, mk2 sporting, with 95k on the clock did 900 miles touch in 5 days and was perfect.

Higher volumetric efficency at the higher rpm + the engine mapped for better mpg around this rev range perhaps? it is a sporting after all if were mapped all for low end stuff then it would go anywhere near as quick

something like that isnt it MadMan0,my old capri 2.0 litre s was very fuel efficient at 80mph but dreadfull at the legal 70mph
of course the fuel computer might be faulty,it is a fiat after all
(ducks down quick before incomming)

The trip meter seems to be about spot on, as comparing it with the brim to brim method.


Madman0, that seems to make sense, Thanks alot.

Drive on the torque peak and you will get the best economy. Shifting up too early wastes fuel as the engine cant get into its stride.

One of my diesels gets 44mpg at 56mph but 59mpg at 70mph.

I have a 900cc bike (8V air cooled fed by four CV carbs) that makes 90bhp. Above 85mph the fuel consumption suffers badly (aerodynamics worse than a housebrick) but revving to 7000 in each gear give the same or better economy than revving to "only" 4 to 5K. Torque peak is 7500 Power peak is 8500.

I am interested in testing this idea out. Anybody know the torque peak for a mk2 1.2 16v sporting? gotta brim the tank later and at 70 mph 6th gear 3.2k revs ive been getting ~48mpg so have something to compare too

Just reading the Haynes manual and can't find specific's on Torque Peak but found that the fuel pump will push 110 litre's an hour if thats any good to you re: mpg, seems the 8v has a better pump (on paper) as it pushes 120 litre's an hour.
If I find it I'll edit this post unless someone beats me to it.

Edit: for you mathematical boffins out there here is whats listed in the book in very small print:

*It is common practice to convert from miles per gallon (MPG) to litre's/100 kilometres (L/100km) where MPG x L/100km = 282.

Not exactly sure if it's useful but I bet someone somewhere can put it into laymans terms and put it into everyday use, if not here are the equations listed in the conversion factors page:

MPG (Imperial) x 0.354 = km per litre (km/l) x 2.825 = MPG (Imperial)
MPG (US) x 0.425 = km per litre (km/l) x 2.352 = MPG (US)

tonyprice1877 said:

I am interested in testing this idea out. Anybody know the torque peak for a mk2 1.2 16v sporting? gotta brim the tank later and at 70 mph 6th gear 3.2k revs ive been getting ~48mpg so have something to compare too

Click to expand...

1.2 8v - 60hp, max power @ 5k revs, max torque @ 2500 rpm
1.2 16v - 80hp, max power @ 5k revs, max torque @ 4k revs
1.4 16v - 95hp, max power @ 5800 rpm, max torque @ 4500 rpm
1.8 16v - 130hp, max power @ 6300 rpm, max torque @ 4300 rpm
1.3 Multijet - 70hp, max power @ 4k revs, max torque @ 1750 rpm
1.9JTD - 85hp, max power @ 3500 rpm, max torque @ 1500rpm
1.9 Multijet - 100hp, max power @ 4k revs, max torque @ 1750rpm

ok well ~85 mph is 4k revs and i got 38 mpg then slowed to 70 at 3.2k and got 50.4 on a motorway run. Might work better to accelerate hard at the torque peak but not to sit at it

science at its best lol

The 60 engine will be struggling at 85 and way above its torque curve so could be expected to have poor mpg. The 1.2 16V is probably right on the money at that speed.

WhiteSei said:

The 60 engine will be struggling at 85 and way above its torque curve so could be expected to have poor mpg. The 1.2 16V is probably right on the money at that speed.

Click to expand...

I have the 1.2 16 v

car not struggling but get much more mpg at lower speeds

WhiteSei said:

Drive on the torque peak and you will get the best economy. Shifting up too early wastes fuel as the engine cant get into its stride.

Click to expand...

:yeahthat:

Since mapping and tuning I notice I get best economy bang on 80mph on the speedo :devil:.

i notice with my 1.2 8v punto i got more mileage driving it at 70+mph!!!

strange huh!

But at 85 the 60 would be struggling so mpg should drop. That said when your foot is on the floor the engine has less throttle/pumping loss - like a diesel (which has no throttle valve) so although going flat out its actually at peak efficiency.
I had a Seicento 900 that daily went more or less flat out up the Cheshire M6 yet I was getting over 45mpg (10, maybe 11 miles per litre). It didnt do much better at slower speeds.

I found at 80mph (motorways are 75mph here, rebellious me :devil revs approx 3750, my mk2 was very economical as compared to on the regional roads which are 50mph, it drank petrol gradients of the roads will affect your mpgs, motorway going downhill?

Ordinary roads wont let you move at constant speed so use more fuel. Then you get the "never more than 10mph below the speed limit" brigade (so annoying) who you'll want to overtake.

I did the test on the same journey to work at different speeds. wish mine was more economical at high speeds

petrol prices as they are 10 mpg to slow down 10pmh seems a very good deal tbh

Wouldnt be so bad but these folks unpredictably speed up & slow down for no good reason so you cant benefit from the slow speed and have to watch them like a hawk. Other road hazards then become even more of an issue.

Going slow is fine but allow others to overtake if they want to. Excessive slowing for bends and speeding up (eventually) on straights is a waste of fuel and does nothing for road safety.