Anyone know what gets the better mpg
Depends on the work it’s doing. I have heard good things about R500 fuel consumption, I have heard of people getting genuine figures of over 9mpg on general haulage which is amazing for a V8.
FH480’s are pretty good as well, I’ve personally had 9’s (tank to tank) on general haulage if I drove it properly, and could even squeeze a bit more out on a long motorway run.
Not sure on the 520’s, never driven one any distance. It’s a turbo-compund engine so should be better than most on heavy work, but will always struggle to compete at average weights due to having more moving parts and hence more mechanical drag than a single turbo unit.
Gogan:
.Not sure on the 520’s, never driven one any distance. It’s a turbo-compund engine so should be better than most on heavy work, but will always struggle to compete at average weights due to having more moving parts and hence more mechanical drag than a single turbo unit.
Except that turbocompounding actually produces the extra power from the exhaust gases downstream of the turbo, so it’s free power, it doesn’t need extra fuel, yes there are more moving parts and a hydraulic coupling to the flywheel, but the power gains overcome the power loss used to produce them 
I was under the understanding the 480 520’s are the same engine just different chips though?
I ask because Iv been from Norfolk to Milan and now I’m at Macon 32 ton gross down same back and my 54 plate fh 460 computers reading 7.8 mpg so actual mpg probably nearer the 7.4 mark. It was windy on the way down but even so think this old girls costing me money now but don’t want to upgrade to a equally bad motor.
I keep hearing daf’s the way forward for mpg but don’t trust the bloody things as far as I could throw one mech/electronically so It out of the 2 swedes
newmercman:
Gogan:
.Not sure on the 520’s, never driven one any distance. It’s a turbo-compund engine so should be better than most on heavy work, but will always struggle to compete at average weights due to having more moving parts and hence more mechanical drag than a single turbo unit.
Except that turbocompounding actually produces the extra power from the exhaust gases downstream of the turbo, so it’s free power, it doesn’t need extra fuel, yes there are more moving parts and a hydraulic coupling to the flywheel, but the power gains overcome the power loss used to produce them
But that only provides a benefit if you’re using all the power, all of the time. That’s great in a radial airplane engine (where turbo-compunding cut its teeth) which constantly ran at high power settings, meaning long runs at constant rpm’s and manifold pressures… A truck engine as you know will rarely spend any significant time producing full power as corners, downhill slopes and speed limiters all conspire to constrain the time the engine spends in the power band.
Any time the engine is not operating in the power band the turbo-compounding cannot be anything other than a disadvantage, it’s just weight and drag that you don’t need, sapping up fuel (albeit not directly as you say, just as a consequence of adding mechanical drag at a time when you want to minimise it).
Yes mechanical drag is one of the four factors in fuel economy, the other three being thermal efficiency, rolling resistance and aerodynamic drag, but although it adds to the mechanical drag it also increases the thermal efficiency, so the question is does the increase in thermal efficiency compensate for the added mechanical drag?
I think it does, the biggest impact on diesel use is getting started or pulling uphill or into the wind, in both cases turbocompounding and its free extra power will require less of the precious liquid for every hp produced, on a light throttle with a light load on flat ground turbocompounding would be of little benefit, but as soon as you start to work the engine then it becomes a benefit.
One thing for the OP to bear in mind, you mention running into the wind, that can have a dramatic effect on mpg, you’re also using winter blend fuels right now, they can, depending on the quality, have a detrimental effect of up to a full mpg.
460MC:
I was under the understanding the 480 520’s are the same engine just different chips though?
I ask because Iv been from Norfolk to Milan and now I’m at Macon 32 ton gross down same back and my 54 plate fh 460 computers reading 7.8 mpg so actual mpg probably nearer the 7.4 mark. It was windy on the way down but even so think this old girls costing me money now but don’t want to upgrade to a equally bad motor.
I keep hearing daf’s the way forward for mpg but don’t trust the bloody things as far as I could throw one mech/electronically so It out of the 2 swedes
R500 Matt you know it makes sense 
I run alongside some R480 Scanias theyre economical but big trouble, they’re getting replaced with R500’s, mines a 520 & I can’t get the same fuel economy as either of the Scanias on the same work. The newer 480 Volvos are very good on fuel I’d put the 480 FH in front of the 520 myself…
Iv taken into account the winter fuel blend and the wind but still think 7.4 on a run at 32 ton ain’t enough.
I drove a 520 little while ago wasn’t overly impressed with the power in comparison also spoke with a Volvo dealer and he had reports of 480’s leaving 520’s obviously that does sound a bit suspect but couldn’t work out what his angle was if any.
R500 was the plan Dafydd but was with lad last week on distance work in R620 computer was reading 6.6 lol
If you want fuel economy a Scania beats a Volvo hands down & always has…
460MC:
Iv taken into account the winter fuel blend and the wind but still think 7.4 on a run at 32 ton ain’t enough.
I drove a 520 little while ago wasn’t overly impressed with the power in comparison also spoke with a Volvo dealer and he had reports of 480’s leaving 520’s obviously that does sound a bit suspect but couldn’t work out what his angle was if any.
R500 was the plan Dafydd but was with lad last week on distance work in R620 computer was reading 6.6 lol
bastrucks.com/vehicles/tract … /4X2/40463
here’s one for you bud, good power, good on fuel
or you coulld look at a R420 and having it mapped to 500, pull mega well and get very good mpg
also was talking to a chap down felixstowe who drives a R620 on containers for artrans, all there trucks are V8’s and they get good mpg out of them, more power less engine is working 
newmercman:
so the question is does the increase in thermal efficiency compensate for the added mechanical drag?
Again, it depends on the work I think. At heavy weights (or, stop-start traffic and/or hilly terrain) its easy to sing the praises of turbo-compounding all day long, you are basically getting horsepower for free, which will get you up to speed (and hence operating more efficiently) in the shortest time possible. But then again, if you are cruising along the motorway with a light load, with the speed limiter dragging you back like a choke-chain, then the turbo-compound is hardly getting the chance to do anything and hence is more of a mill-stone round your neck. It’s horses for courses.
Also, don’t forget that modern EGR systems remove a lot of the thermal energy from the exhaust gases before it makes it to the turbo, so much of the thermal efficiency benefit of the turbo-compound setup is stolen and fed into the cooling system instead.
Gogan:
newmercman:
so the question is does the increase in thermal efficiency compensate for the added mechanical drag?Again, it depends on the work I think. At heavy weights (or, stop-start traffic and/or hilly terrain) its easy to sing the praises of turbo-compounding all day long, you are basically getting horsepower for free, which will get you up to speed (and hence operating more efficiently) in the shortest time possible. But then again, if you are cruising along the motorway with a light load, with the speed limiter dragging you back like a choke-chain, then the turbo-compound is hardly getting the chance to do anything and hence is more of a mill-stone round your neck. It’s horses for courses.
Also, don’t forget that modern EGR systems remove a lot of the thermal energy from the exhaust gases before it makes it to the turbo, so the much of thermal efficiency benefit of the turbo-compound setup is stolen and fed into the cooling system instead.
Ahhhhh EGR, I’ll quote from the man at ■■■■■■■ who came up with the idea ‘EGR is the worst thing you could ever do to a diesel engine’ 
As for turbocompounding, we’re both singing from the same song sheet
newmercman:
Ahhhhh EGR, I’ll quote from the man at ■■■■■■■ who came up with the idea ‘EGR is the worst thing you could ever do to a diesel engine’
Agreed, though to be fair I’ve found that as long as you keep the system clean (and by clean I literally mean make sure it’s not full of black sooty ■■■■) then it is reliable and does its job. I would have EGR over SCR any day of the week, all other things being equal.
newmercman:
As for turbocompounding, we’re both singing from the same song sheet
So it would appear. 
I never thought the 520 was a turbo compound engine, the old 500’s were and they went well but they liked a drink and the turbo compound unit was expensive when it went wrong
the newer 500’s are egr as an option but i dont like the idea of putting dirty hot exhaust gas back into the cylinders!
the later 13 litre engines are not a patch on the 12 litre anyway when it comes to reliability… but then again the 12 litre 460’s wernt the best on fuel!..heard many horror stories about these 13 litre …side plates leaking,diesel in the oil,oil in the water,injector seals,side plates again!..
i think i will stick to my old 460!
moose
Fly Sheet is on the money, the Scania 6 pot is better on fuel than the Volvo, back in my road tester days the 420 Scania was at least .5mpg in front of the 420 Volvo…but the 430 V6 Merc beat them all, which came as a surprise to me (and the blokes at Scania )
newmercman:
but the 430 V6 Merc beat them all, which came as a surprise to me (and the blokes at Scania
The later V6 Merc (460, and to a lesser extent 480) engines are just as good, and the Straight-6’s in the Axors are extremely frugal as well.
The V8’s a thirsty beast even if driven gingerly, but you can’t have it all.
Gogan, it may not come as much surprise to learn that I am a big fan of things that wear the three pointed star
I’d take an Actros over any of its competitors, the 460/480 is more than adequate for anything except heavy haul, I’d go for either one of them, or you could wait until the new in-line 6 comes out, it’s been used in North America for the last few years under the Detroit Diesel banner, there’s an 11, 13 and 15ltr option, the 15ltr also has…turbocompounding it was designed from the ground up to have all the emissions reduction crap on it, so you’ll get the whole alphabet soup of EGR, DPF and SCR, but so far they’ve been reliable and are achieving fantastic economy, over 8 miles to the smaller US gallon is par for the course, but with all the technological junk bolted on, you don’t want to get one made on a Friday afternoon, especially as the Merc service network is the biggest drawback to owning a Merc
The V8 Scanias aren’t that bad on fuel compared to similar trucks. We’ve an R500 and R580 both returning just over 7 mpg. The 1854 Merc is returning 6.5 on the same work and an FH500 is getting bang on 7 mpg.
Point to bare in mind the FH has a good engine brake you’d need to spec a Scanny with a retarder