Are classic car mpg ratings accurate?

[artdjones]

The two nations that seem to have always been able to get good real world economy figures on humdrum cars are the French and the Japanese, even back in the pre efi days.

The company that couldn't do it back then was Ford, even the mk1 Fiesta only doing 28-29

[wuvvum]

28 minutes ago, New POD said:

I tried comuting from L37 to The Arse end of Burnley in a 1.4D echo.  Every day.  50 mpg was not achievable.  

The fucking thing was so gutless that you had to rag the arse of it.

Not helped by the Hills on the M65. If I wanted to not slow down to 55 mph on the uphill sections, I needed to hit 95 mph on the downhill sections.  

Also not helped by the AX GT wheels and 175 tyres instead of 145. 

The 1.5D I had managed around 65 mpg on a steady run to Somerset and back.

[AxWomble]

53 minutes ago, cort1977 said:

Magazine claims, and even more so manufacturers figures up to diesel gate, are a load of tosh.

I reckon a Citroen AX diesel would be hard to beat for real world, i.e. able to run steadily at 70, fuel economy.

Our ph2 106 1.5D does around 65mpg across a 5-600 mile tank, pretty much every tank. Dips by about 2mpg during winter. This is with a fair bit of town driving and lots of country A roads - 5 miles of derestricted, then a village at 30mph, then another 5 miles of derestricted, etc, etc. Not the most economical circumstances to be in! On motorway runs with low levels of town driving, it cracks 70mpg without any concentration or weird hypermiling tactics required.

 

We had a petrol 1.0 AX beforehand that did 47mpg regardless of how you drove it - I reckon an AX diesel would be hitting 65mpg on every tank due to lower weight - our car has far more metal body panels than an AX, heavier construction in general, power steering, central locking, leccy windows, along with actual interior trim and comfort*. 

[AxWomble]

50 minutes ago, New POD said:

I tried comuting from L37 to The Arse end of Burnley in a 1.4D echo.  Every day.  50 mpg was not achievable.  

The fucking thing was so gutless that you had to rag the arse of it.

Not helped by the Hills on the M65. If I wanted to not slow down to 55 mph on the uphill sections, I needed to hit 95 mph on the downhill sections.  

Also not helped by the AX GT wheels and 175 tyres instead of 145. 

As I proved by mis-timing by 106 last month, a few degrees in the wrong direction on the injection pump can have catastrophic consequences! Ours was dog slow, now it’s merely ‘slow’ - I jest, it actually feels quite perky when in proper tune, and can certainly hold 70 up any motorway hill I’ve had the pleasure of climbing. 

[New POD]

1 hour ago, AxWomble said:

As I proved by mis-timing by 106 last month, a few degrees in the wrong direction on the injection pump can have catastrophic consequences! Ours was dog slow, now it’s merely ‘slow’ - I jest, it actually feels quite perky when in proper tune, and can certainly hold 70 up any motorway hill I’ve had the pleasure of climbing. 

Shit. You know what. I reckon that's it. 

I once fucked up a cam Belt change, and it took me ages to get all my marks to line up. I bet it ended up one tooth out. 

Take me back to 1997 to do it again properly. 

[AxWomble]

50 minutes ago, New POD said:

Shit. You know what. I reckon that's it. 

I once fucked up a cam Belt change, and it took me ages to get all my marks to line up. I bet it ended up one tooth out. 

Take me back to 1997 to do it again properly. 

That’s probs the issue - made even worse by the fact that it’s actually possible to be LESS  than a tooth out;  barely perceptible levels of rotation seem to make a massive difference. Pulleys that rotate on their hubs means that paint marks are basically null and void too. I did not enjoy it, the first time or the second time round! 

[dozeydustman]

I wasn’t much of an mpg enthusiast while I was in my late teens and early 20s, until I got my first Scimitar. I averaged 35mpg across the board from my Samba, Horizon and 205s, but to be fair I didn’t do massive drives mainly commuting to and from school/work/uni.

90 litre tank in the Scimitar could be drunk quite quickly if I hooned it everywhere. Averaged low-mid 20s in urban driving, but long hauls it was quite thrifty, having the overdrive ratio changed at a rebuild really helped for 35-40mpg driving quite sensibly. At 70 it was doing around 1700rpm. The second Scimitar was an auto and much lower geared, 3200rpm at 70 and the best I got from it was 29.8mpg on a blat from Canterbury to Normandy using Super Unleaded, doing 55-60 as it pissed down with rain.
 

I did keep the engines in my older cars well maintained and the carbs tuned every 6 months, which really helped, which reminds me I need to see if the Saab needs a service!

 

[Fumbler]

It's interesting to see the comparison between real data and what the manufacturers gave you. I have some data of my own which concerns my commuting to work and the motorway journeys to college.

My commute to work is 45 miles each way, so 90 in total, and this happens 4 times a week. Most of this driving is through towns and derestricted roads, so speeds vary between 60 and 20. The journey to college is 180 miles and is mostly motorway.

My Micra with its 998cc engine made 53MPG on my last tank commuting to work. It makes ~43MPG doing the motorway journey to college. Before E-10 was introduced, I commonly saw upwards of 55MPG when commuting.

My BX with its 1360cc engine frequently makes ~45MPG while commuting, however, in constrast to the Micra, it also made ~45MPG when I travelled up to college. This is probably due to the taller gearing and more torque at low RPM thanks to the undersquare design. I found that the vehicle was very sensitive to jetting changes and overall carb changes while I was faffing around in that area. At present it's doing the best it's ever done in my ownership. It appears the extra ethanol content has harmed performance in both vehicles.

I also have a fuel efficiency table that I found in the owner's folder that came with the car.