anyone running a 420 ■■■■■■■ just wondering what you are getting mpg
My bros 440 chipped olympic flat with rear crane will do 6.5 to 7mpg matlock to penzance loaded both ways ,with out draw bar trailer it will do 11.5mpg ,but the 380 6legger flat will do over 14mpg
our 420 was doing on distance work pulling a 65cyd ribbed bulker would return 8mpg, on local work it dropped too as low as 5.4mpg
is there anything obvious i should be looking at on the ism engine ive had the engine checked again and all the top end is spot on but the mpg is poor getting around 6 mpg and thats with different drivers i no its got the aerodynamics of a house brick with a 20ft tank in its back but i thought i would squeeze 6.5 to 7 out of it the noise was the top end completely out of adjustment which is now all ok .
Is 6mpg what the road relay says or is that your calculation .
Road relay and the daf fuel consumption fuel figures on the dash display are working out roughly the same
try pen and paper lee and get the correct figures 
dont take computers for figures it may be better then again you may get a shock as well
^^^^^^^^ what the Yorkshire Pie Eating Champion said 
you may be surprised at the results, can’t say which way though
HUBBA HUBBA…
its out but not by much done pen n paper it works out slighty higher its been it to man again ive changed the fuel filter and air filter and try again but i dont think it will change much man said just drive it not much you can do with them other then get reliability out of the ■■■■■■■ lump
I think I would fit a pipe and gauge to the inlet manifold just to check that you have no turbo boost issues whilst you are working it under load.
i used to take mine to ■■■■■■■ at leeds, brilliant service there, dont know if he’s there but a lad called chris farrington was one of the mechanics and last time i went had moved into the office - real top bloke, knew i wanted to learn more about my truck so he let me be involved - the first time i went it was a nice sunny day so rather than work inside the work shop where i wasnt allowed to be he brought the truck outside, that was for a basic health check, i’d only been going for 4 months or so, the truck in question was an erf ec10, which didnt pull very well to say the least, but as i had no experience and nothing to compare it with i just thought it was as it was so i just plodded on until a friend told me he thought it was black smoking, so as test was coming up i booked it in at ■■■■■■■ for a once over, the whole in the intercooler was so big it retained no air pressure what so ever lol - i couldnt believe the transformation a new one made!!! i went back a few times to ■■■■■■■■ the second time was for a misfire which i’d put done to an injector failing, chris came out, listened to my theory and was good enough to actually take my comments on board and see if my theory was right first - which doesnt always happen does it? it was, so while the top end was exposed i asked for it to be set and if i could watch - i cant remember how you would do it now but chris was good enough to give me a hands on lesson as he knew i wasnt just being nosey. you would never get that at fishlake (who i used the rest of the time)
i did hear that the 420’s were not as good on fuel as the 405’s due to alterations to the emission levels?
I have a ism 405 in a rigid which will be on the road soon so ill keep an eye on the mpg,
The l10 STC which is running at the moment has had 3 intercoolers on it over the last few years, when you are losing just a little boost the economy suffers big time, and obviously when you loose a lot of boost you have black smoke and no power on a mechanical engine, but an electronic engine such as the ISM will try to compensate…
Theres no replacement for displacement just get a big cam instead.
A wonderful way to get the tare weight up and the fuel bills with it
our old silver 420 is pulling 9.5 over an avaerage week, she has a ■■■■■■■ tech. ‘top set’ every January and oil/filter change every 35k. she has been with us 8 years and covered 808oookm without the slightest hassle (God willing) this is why she’s still here and poncing over the hill every Year to The Foden Society AGM…I mean it when I say £20k wouldn’t prise my deathly grip off the steering wheel…she’s here to stay.
All the ISM lump wants is respect and and clean oil, they gunge up in no time… we talked with ■■■■■■■ in January about an aftermarket ‘spinner’ similar to Scania’s fitment and that’s on going…
Pelican had 1 shot at a top set for me and it was a disaster… left the gauze filter in the top filthy and caused crankcase pressure with alarming visual effects!
The ■■■■■■■■ chaps at Leeds come out to us in Holmfirth and do a sterling job.
Also, if you open a trade account the horrible price of the correct Valvoline Blue oil drops by nearly half… excellent stuff…
Filters are all Fleetguard even from Pelican so order them from your factor for a pleasant surprise…
oil filter LF9001
Any more questions don’t hesitate, plus there are some top lads on the Foden Society Website.
The guy you need to ask for at Pelican is Steve Birkinshaw… bit of a legend with the Foden kit!!! 
Might be tight injector.Get it checked quick.Once did one and rang ■■■■■■■ for injector lash settings.This motor had oil pressure control on injectors.Set it to what they said and it ran like a gem for 30 miles then dead.
Recoverd the truck and found that every injector cup had cracked where the needle had bottomed out.
1000 quid per injector(ouch) but luckily ■■■■■■■ replaced them for free due to their mistake of giving me wrong info.
Couldnt see the likes of Merc or Volvo ever doing that.