P38 DSE doing 26mpg - is that good??

Hi folks,
I just want to bounce this around other people to see if it sounds like I have a problem causing poor MPG.

Our 97 2.5 DSE (Manual) with 90k on it is driven 28 miles each way to work and back at a steady 60mph till it goes nose to tail in traffic for the last 4 miles, this takes about an hour in total. 30 min's in the traffic and the other 30 min's doing a steady 60mph. (it sounds like a GCSE maths question this...)
The fuel computer can be reset and reads 30mpg on the 60mph part of the journey however when refilling with diesel the car actually works out as 26mpg which is less then I would expect.

On a 400 mile round trip to london and back doing 80mpg steady it worked out at 24mpg!!!! which is mad! The car does have a PSI Powerbox fitted which is meant to improve the mpg but hasn't made a difference really (expect to the power).

I used to have a P38 2.5 DT and it would do 27mpg if I hammered it at 90mph everywhere and 32mpg if I drove is normally. as such I am shocked that this DSE is so much worse on fuel.

What sort of figures does anyone else get out of the manual (or auto) diesels?

Thanks
Richard

that sounds pretty good my mates dse only does 18mpg on average it is auto though.

mine has a superchip fitted and very rarely goes above 22 on the computor i do roughly 16 mile each way daily at about 50 mph my only advantage is it is as powerful as a td6 near enough they do say though if you want economy dont buy a range

Agree with both the replies, my 2000DHSE Auto did 18.4 around town until i fitted a superchip, i now get 22.4 around town and on a decent ( 330mls ) mixed run average 29 8mph

My DT auto does 22mpg to work and back (average speed on trip counter 24 mph), mix of traffic and open road, and 28 on a long run at a steady 65-70.
Though the trip counter gives optomistic mpg readings, the above are worked out on filling the tank up

This is quite amusing. I averaged 20.4 mpg in my 4.6 bringing it home from Sheffield, including going over the snake pass.

With the cost of diesel at the moment, I probably didn't spend much more than a couple of the diesels mentioned here..

Pete-M said:

This is quite amusing. I averaged 20.4 mpg in my 4.6 bringing it home from Sheffield, including going over the snake pass.

With the cost of diesel at the moment, I probably didn't spend much more than a couple of the diesels mentioned here..

Click to expand...

Course living on the continent and running a chipped DSE where diesel is still cheaper than petrol, I'm all the way to and from the fuel station, and getting about 26mpg average and above 30mpg on the autostrada.

I agree with Pete-M
I averaged 19.3 this week included motorway and about town

The autos are normally worse than the manuals. If you're getting a calculated 26mpg then you're doing pretty well.
Mines not running great at the moment (I think its a problem with the MAP sensor but it could be the superchip too) and I'm getting a calculated average of 23mpg on 15 minutes traffic, 35 minutes constant 60 then 15 minutes up a mountain on forest roads.
Your computer is fairly close to mine, I've it corelated over the last 4000 miles that it over estimates the fuel economy by 1/6 so an indicated 28mpg on the computer is calculated at a true 24mpg. On the few occasions that it has run well I've seen over 38 mpg on the computer on the open road so that equates to about 32mpg.
One thing you can do to improve economy around town is to knock it into neutral at the lights or when you're stuck in a jam.

I've got a 99 Dse with 123k on the clock, she gives me about 21 mpg around town and 26mpg on a run, so you sound as if your doing ok!

I've slipped the air con belt off this weekend to see if it helps with the MPG, I've also bought a meter of 3.5mm braded pipe off ebay to replace the injector leak off pipes. I can smell diesel when we're sat in traffic and I notice the injectors are sat in pools of diesel. I doubt this will make a huge difference but its got to be worth a try. With diesel being £1.22 per litre this car could well be short lived!

You know there is a button on the HeVac controls that says 'A/C off' which is supposed to do the same job as taking the belt off but keeps your hands clean
BTW if you are getting a calculated (not indicated) average of 26mpg I've a feeling that its as good as it gets. 2.5 tonne being hauled around by 2.5 litres is not a recipe for good fuel economy.

RSW said:

Hi folks,
I just want to bounce this around other people to see if it sounds like I have a problem causing poor MPG.

Our 97 2.5 DSE (Manual) with 90k on it is driven 28 miles each way to work and back at a steady 60mph till it goes nose to tail in traffic for the last 4 miles, this takes about an hour in total. 30 min's in the traffic and the other 30 min's doing a steady 60mph. (it sounds like a GCSE maths question this...)
The fuel computer can be reset and reads 30mpg on the 60mph part of the journey however when refilling with diesel the car actually works out as 26mpg which is less then I would expect.

On a 400 mile round trip to london and back doing 80mpg steady it worked out at 24mpg!!!! which is mad! The car does have a PSI Powerbox fitted which is meant to improve the mpg but hasn't made a difference really (expect to the power).

I used to have a P38 2.5 DT and it would do 27mpg if I hammered it at 90mph everywhere and 32mpg if I drove is normally. as such I am shocked that this DSE is so much worse on fuel.

What sort of figures does anyone else get out of the manual (or auto) diesels?

Thanks
Richard

Click to expand...

Hi rich,
dont know if thats good for a DSE or not.. i have a 4.6 and going to anglesey(125MILES) I GOT 24.3MPG THE COMP READ 24.5...on the way back the comp read 24.7 and on fill up to the very top it worked out at 24.6mpg... c/control set at 60 both ways...

SpudH said:

You know there is a button on the HeVac controls that says 'A/C off' which is supposed to do the same job as taking the belt off but keeps your hands clean
BTW if you are getting a calculated (not indicated) average of 26mpg I've a feeling that its as good as it gets. 2.5 tonne being hauled around by 2.5 litres is not a recipe for good fuel economy.

Click to expand...

Yeah I know but I had a few friends who worked at Vauxhall and people were always asking them to actually remove the aircon belt as the drag of the idler pulley and aircon pump itself caused a reduction in mpg. Honestly I used to have a 2.5 DT (N654 BKH I think it was if its still out there) no aircon or anything and that had 167,000 miles on it when I sold it! I used it for work. It did 27mpg if I hammered it at 90, and 32mpg if I took it steady. This is my second Range Rover and I was shocked when this one only did 24-26. This government doens't help... but thats another story.
Cheers
Richard

Using aircon consumes less fuel than driving with a window open. I know which one I prefer. Being cool, comfy, quiet and airconned sure beats the hell out of the window option.

There's also the fact that if you remove the belt, you can't use the AC for a couple of minutes a week - which means the AC will go hideously wrong within a few months of the belt being cut.

I, for one, wouldn't buy a P38 with broken or malfunctioning aircon, and the seller telling me that "It's fine, just needs a belt" wouldn't convince me that his was the Rangie to buy.

So to save 0.2 mpg you're making your car uncomfortable and a lot more unsaleable. Sounds like a top idea.

I take your point but in my experience the difference in MPG is more like 3 or maybe 4mpg. I've had other cars with aircon and I couldn't believe the difference in ecomony.
I've just received advice in another post that when the aircon light is on the aircon is actually off - which I didn't know. That being the case it would seem I've been running with the aircon on.
Anyway, it takes about 10 min's to slip that belt back on so I aren't too concerned either way. I'm just hopeful to see an increase in MPG.

Ive just had a read of this post and if you want the best fuel economy you can then use the cruise control wherever possible. That way the computer fuels the engine at just the correct amount.

I do a longish journeys almost every other week to Nottingham, about 70 miles to get there and the same back. In the week when my radio was away at Roverville being refurbished I had to make this trip and to pass my time (yes I was very bored) I started messing about with the trip computer and different driving styles to see what would get me the best MPG. I essentially turned into a mini Jeremy Clarkson when he drove that Audi A8 to Scotland from London and back again on tank of fuel.

I found that the 'sweet spot' for my DSE was at around 73/74mph. At this speed with cruise control on and the A/C on I averaged around 31.3MPG. This was on the M1 over about 10 miles with hills and one queue, at this speed you are usually at a comfortable cruising speed and generally are 'in time' with the rest of the vehicles on the motorway.

Now when I do the same run to Nottingham I usually set the cruise at 70mph, A/C on, radio on and just sit back and enjoy the ride (although at this speed everyone usually passes you and you have to concentrate a little more on whats ahead to be able to keep the cruise control on). I have managed...



...when doing this. This calculated as pretty much spot on when I calculated it at the pump.

If you want to be super dooper fuel saver man of the year then turn off the radio, turn off the A/C and get behind a lorry doing 56mph and set the cruise control. Drafting a safe distance from a lorry will see you massive gains in MPG - I found this out during my trip of boredom.

Basically, as I said at the beginning of this post, my advice would be to use the cruise control whenever and wherever possible.

-Wills

sell it and get a petrol engine converted to LPG...........now believe this on not.........i filled up with LPG at greenwich ( £21 for nearly 40 ltrs ) i drove 40 miles to Southend,i still had a full tank of LPG showing so i filled up again to see what the mpg was.............£2.52p is all it would take the LPG was 53.6p per ltr that works out at nearly 40 to the gallon.........i still can't believe it myself.............its not so good around town tho'