280i MPG - What's Average

280i MPG - What's Average

Author
Discussion

v8s4me

Original Poster:

7,234 posts

218 months

Sunday 30th April 2017
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I done a few runs now and my average is around 25mpg. This seems a bit low. How does it compare with others?

mrzigazaga

18,534 posts

164 months

Sunday 30th April 2017
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Hi mate


As far as I can remember that sounds about right...smile

pk500

1,973 posts

211 months

Sunday 30th April 2017
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25 you need to drive it harder

phillpot

17,105 posts

182 months

Sunday 30th April 2017
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v8s4me said:
. This seems a bit low.
Have you checked for fuel leaks? .... wink

v8s4me

Original Poster:

7,234 posts

218 months

Sunday 30th April 2017
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Sounds like I need to bring the 5-speed 'box conversion up the priority list laugh

marcus1875

1,512 posts

141 months

Monday 1st May 2017
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I average 24mpg. Although on 350 trip a couple of weeks i got 31mpg, but that included about 150m stuck at NSL.
Marcus

celcius

688 posts

254 months

Monday 1st May 2017
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As paul says , you need to nail it a bit more :-)

v8s4me

Original Poster:

7,234 posts

218 months

Monday 1st May 2017
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30mpg ish was what I was expecting based on what I know the 'S's with the 2.8 engine do. But these have a 5-speed 'box so that obviously helps a lot.

SEvans

1,159 posts

266 months

Monday 1st May 2017
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I suspect a Wedge weighs a fair bit more than an S so that's not going to help either.

Cheers Steve

mrzigazaga

18,534 posts

164 months

Monday 1st May 2017
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SEvans said:
I suspect a Wedge weighs a fair bit more than an S so that's not going to help either.

Cheers Steve
Is this with or without driver Steve..hehe

I lost two stone in weight and I tell you what.......The Wedge is no faster...laugh
(Well marginally)...smile

As I always say to people when they ask what the MPG is of a Wedge ..."Its not MPG...Its SPG"....Smiles Per Gallon..smile , of course its nice to know roughly what they do but how you going to work it out????...Reading the Wedge fuel gauge...rofl

v8s4me

Original Poster:

7,234 posts

218 months

Monday 1st May 2017
quotequote all
mrzigazaga said:
.... of course its nice to know roughly what they do but how you going to work it out????...Reading the Wedge fuel gauge...rofl
That's why it's handy to know. So you know when to look for a fuel station regardless of what the fuel gauge says. wink

mrzigazaga

18,534 posts

164 months

Monday 1st May 2017
quotequote all
v8s4me said:
mrzigazaga said:
.... of course its nice to know roughly what they do but how you going to work it out????...Reading the Wedge fuel gauge...rofl
That's why it's handy to know. So you know when to look for a fuel station regardless of what the fuel gauge says. wink
Yes I agree...Its more about what you have put in and how far you are going.....Id personally say base it on 24 MPG..Thats what I do with the V8..although a more conservative figure is 22 SPG is generally applied...Anything over is a bonus...smile



marcus1875

1,512 posts

141 months

Monday 1st May 2017
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The guage being as accurate as they are, i put 20litres in every 120 miles or so, which works out at appx 24mpg.
I do recall getting 13mpg when i first got it. It was very rough
Marcus

Edited by marcus1875 on Tuesday 2nd May 14:03

TasminTim

3 posts

105 months

Tuesday 2nd May 2017
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My '86 was less than 24mpg until I took injectors out and attempted to clean them.
Helped a tad but not as good as hoped.
Over the winter I ordered and installed a brand new set of 6.
Have been out for a run only once for a 50/60 km spin as weather is cold and wet here but already noticed better performance and the gauge didn't drop as bad. Can't wait to do a full measurement.
A chap with decades of Jag experience, I met a year or two ago, told me that the first thing I should do after purchasing the 280i was get new injectors.


RCK974X

2,521 posts

148 months

Wednesday 3rd May 2017
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(1982. 4 speed, std engine and gearing)

When proper 4* leaded was still sold, I would get 28-30mpg on a decent run, and even commuting to work, as I went a fair way on the motorway (~30 miles) with the top down at 70mph (OK, under 80, most of the time).

With the unleaded 95 crap today, 26-28mpg on 'A' roads (equiv), again with not much traffic and mostly at 65 (ish) = 100kph limit.

Yes, I got new injectors too - I reckon it made more of a difference in smoothness (especially light throttle) than in economy.

But as said, it all depends on how you drive, not so much what speed, but how hard you press the go pedal.


Info - to get smooth running and no pinking, I had to retard timing a little, and disconnect vacuum advance.
You can tell it's not quite as 'sharp' when you hit the pedal, so I reckon that's the mpg difference.

Just for comparison, my Aussie built Toyota Aurion (Camry with the Lexus V6 motor) is 3.5 litres, 270bhp, (5 seater large sedan), gives me 30-32mpg overall, and an astonishing 36-38 mpg on 100kph cruising with very few stops, on unleaded 91, driven in the same style, and it's MASSIVELY quicker for overtaking a truck, even though it's via a slushbox. BUT it's BLOODY BORING to look at...

Just shows how far the engine technology has moved on.

RCK974X

2,521 posts

148 months

Wednesday 3rd May 2017
quotequote all
And now I remember the carb 2.8 was almost the same, 27-28mpg on a motorway run (Granny, 5 speeder), compared to 24-26 for the Essex (Scimitar)
so economy didn't change much, Carb to K-jet.

Tip -

Are you sure brakes aren't dragging ? Or even bad tracking can shave economy.
Rear hbrake not releasing properly is VERY common on the wedges...

Edited by RCK974X on Wednesday 3rd May 06:23

v8s4me

Original Poster:

7,234 posts

218 months

Wednesday 3rd May 2017
quotequote all
RCK974X said:
..(1982. 4 speed, std engine and gearing)....Info - to get smooth running and no pinking, I had to retard timing a little, and disconnect vacuum advance......
That's interesting. Mine was misfiring under hard acceleration. I disconnected the vacuum pipe and there was a noticeable improvement. When I first got the car running the timing was retarded so I reset to 12 degrees BTDC. Should I wind it back again I wonder? What advance are you running yours at?

RCK974X said:
....Are you sure brakes aren't dragging ? Or even bad tracking can shave economy.
Rear hbrake not releasing properly is VERY common on the wedges...
Yes, all that's been done.

Sounds like there is no real economy penalty for converting to carb and a lot fewer problems.

mrzigazaga

18,534 posts

164 months

Wednesday 3rd May 2017
quotequote all
v8s4me said:
RCK974X said:
Mine was misfiring under hard acceleration. I disconnected the vacuum pipe and there was a noticeable improvement. When I first got the car running the timing was retarded so I reset to 12 degrees BTDC. Should I wind it back again I wonder? What advance are you running yours at?
Hi Joe

I used to use super unleaded with a wynn's lead replacement additive every 5th tank...My timing was most happy at 9.5..I would definitely wind it back to around 10....smile

RCK974X

2,521 posts

148 months

Wednesday 3rd May 2017
quotequote all
v8s4me said:
That's interesting. Mine was misfiring under hard acceleration. I disconnected the vacuum pipe and there was a noticeable improvement. When I first got the car running the timing was retarded so I reset to 12 degrees BTDC. Should I wind it back again I wonder? What advance are you running yours at? <snip> Sounds like there is no real economy penalty for converting to carb and a lot fewer problems.
Mine was pinking (detonation) at 12 with foot down, and bucking/misfiring at low speed cruise in traffic. After playing around a lot, I ended up at 10.5 degrees and no vac advance (bucking was down to the vac advance). Also fitted colder plugs - N7Y instead of N9Y, which helped with the pinking. They haven't fouled so far ... unleaded burns a bit hotter than leaded anyway (according to what I've read) .

(Ford recommend 9 degrees for unleaded instead of 12, so mine is exactly half)

All you can do is play around to get the best and keep noting wot's better or worse...
I even tried limiting the vac advance with a bolt, but made no difference.
This is New Zealand so gas mix probably a bit different to UK, who knows !

Carb drops the power a bit, but not the torque, so still cruises well, but a bit slower to pass.

You CAN just swop manifolds, cams are identical in early engines, but use the carb dizzy if you can.
38DGAS carb from Essex actually works well as I understand, and better than original Solex. Bolts straight on.
Do NOT use 2.3 manifold, they are slightly different and will leak water into oil.