Topic: 350SE fuel consumption

[Denis]

Hi everyone

I just returned from a Christmas trip (Paris-Quimper-Paris). For a total of 1200 km of which 1000 on fairly flat land and 200 in hilly terrain, with 3 persons on board and their luggage, at an average speed of 110kph on mostly smooth french "autoroute", I got 13,7 litres/100; this is about 18.3 US MPG or 20.7 IMP MPG.

I drove as smoothly as possible. I think that is pretty good considering the load.

Just another W116 fuel consumption post.

Denis

Paris, France

[Mforcer]

Thanks for the post. That is very impressive consumption. Gives me incentive to see what I can achieve on my next good drive - we may need to have a competition

[oscar]

Hey Denis, 

Last time I calculated my 350's consumption (well over a year ago) it was between 14-15 L/100 km and I think around 19 mpg.  That was after a 400km trip on all flat terrain.  I should write these things down.

But since then I it's had a bit of work to the running gear and suspension, and at the moment is in the shop having new valve stem seals, timing chain and a few other bits seen to.  Cylinder 7 has been down on compression and had a threaded spark plug hole.  It'll have a new thread put in and hopefully the 7th piston and rings are undamaged.

It'll be interesting to see if the work will lead to any increase in power and economy.  Will post details when all is done.

By the way Denis, our new car with 15000km is a ford territory,an awd 2 tonne car and does about 13.5 L/100km on 1300 km round trip to the coast, 16 L/100 around town.  It's a 4litre in line six with modern engine management stuff!  So I reckon your figures hold up pretty well.

[Denis]

Hi fellows

My 350SE is automatic. I took the trip with new spark plugs and using a technique of gently accelerating downhill to gain speed that I would loose going uphill right afterwards. I did floor the throttle a few times :-)

I think that holding a relatively steady low speed helps to level differences between the V8s : it only takes so much power to maintain 110 kph on level ground and while a larger engine should use more fuel it may also gain in efficiency by running lightly loaded somewhere around maximum torque. Moving at 180 kph, I bet that the 350 would use significantly less fuel than a 6.9.

In France, one cannot modify an engine at all with the exception of LPG conversion. Ideally I wish my car had 11.0 compression and a five speed. It would help fuel consumption figures. While engine management electronics would help, I think that variable valve timing is the miracle worker of today's engines : you can manage spark and fuel volumes but if the cylinders do not fill/exhaust efficiently depending on load and speed, the results will be less impressive.

In any case, just imagine the figures we would get with these V8s using a classic set of four Zenith 35/40 twin barrel carburettors as used in my old 230 ! I bet we would all be using 25l/100km !

Regards


Denis

Paris, France

[Denis]

Hi Styria

Thanks for the interesting post. Here in France, the autoroute speed limit is 130 kph but most people go for 140 and look up where the speed radars are located on the Internet :-)

I will try an estimate at 130 when I go to Bordeaux this spring to visit Paul Bracq. BTW, the official factory spec for a 6.3 going flat out is 31,5 liters per 100 !!! airplanes are cheaper on fuel :-)

A few years ago, I drove at a sustained 180 on a new stretch of autoroute (A84 from Caen) and the car was just lovely to drive - hence a comment I've heard : a TGV on wheels.

For those not knowing, the TGV is the high speed train that is used on all express railroads in France : cruises at 180-200, hits peaks of 220. At 200, the wins a glass doesn't even move thanks to computer-controlled air suspension. So a TGV on wheels is indeed a great comment !

Regards

Denis
Paris, France

Ozbenzhead, don't worry, more than one trip to Bordeaux is planned ;-)

[AMG69]

Hi Gents, just back from South Australia; put about 1500kms under the 6.9's new wheels (refurbished 16 x 8 Pentas) and achieved an average of 16l/100km's on mainly country driving around South East SA, with admittedly very little long straight stretches - ie I am certain 15l/100 is easily achievable, esp at 100kmhr; this was the longest driving i have done since I bought it and I have to say it impressed me for a 28 year old car; effortless all day at 110, infact it really felt better at 130-140.  Did one long overtaking pass (a B double - ie extra long semi trailer truck) and reached 180 before bringing the old girl down to legal speed again. amazing.
Oh and the Nieces and nephews had the electric rear seat and rear windows moving up and down more than they have in about 20 years I think!
As for the air cond - coped pretty well (new gas and new r/dryer fitted three weeks ago) but it is nowhere near as cold as the old gas.  When I bought it it was so cold on the old gas that it used to have "fog" coming thru the centre vents - scared the crap out of me when i first used it as I thought I had a fire in the engine bay until I realised there was no burning smell!
Oh and the day I arrived in Adelaide it was 42.5 degrees C; at 110km/hr on the South Eastern freeway in 42.5degree C heat the car sat on about 85 on the temp gauge - that really impressed me!

[editjunk]

As I've posted before, I get around 300kms to a full tank (85 litres?) on city drives, and 500 km @ 100 - 110 kmh on country driving with my 1973 350SE. I floor it occasionally: the climb out of Woolongng is too much fun to take slow... Why do I feel I'm getting really shitty mileage? You guys must have your engines really pinging.

(PS Styria: I owe you $15 - where can I post a cheque?)

- editjunk

[Denis]

Hi editjunk

I understand, you poor milleage reflects a feature of the 3.5 engine that we must somehow learn to abandon or enjoy  : they really sound good over 5500 rpm - the music of a high-revving, short stroke, small displacement, non-pushrod V-8 sounds wonderful!

On the other hand, we are not pinging (pinking?)  our engines, the 3.5 camshaft provides good torque across a wide rpm band. The engine is just relaxed at 110 kph. But the 4.5 is better adapted to a W116's weight as the 3.5 torque peak is at 4000 rpm. I can live with the compromise.

That is also why I am convinced that the 3.5 was designed for the W113.  Of course the W113 would have needed a W114 suspension to use that power.

It's your wallet, enjoy as you see fit 


Denis

Paris, France

NB - Most W116 clubs in France feel that the best engine for a W116 is the 4.5 : power available at most speeds and reasonable fuel consumption when decide to cruise fast on an autobahn, autostrada or even cheat on a french autoroute 

[Denis]

Good point styria !

Much depends on terrain for fuel consumption figures.

But of course, the rich Swiss never had fuel consumption problems driving 6.9s up and down alpine hills 

Denis

[oscar]

Holy crap!!!  Got my 350 back yesterday from the workshops, did 186km and used 20.1 litres, thats about 10.8L/100 with about 15 km city driving, the rest highway at 110km/hr, a few hills but definitely no mountains, no luggage and a full tank.  The tank was half full with regular unleaded then topped with 98 RON unleaded.  A bit pedantic with details but they're there for the curious, the figure's a bit unbelievable.  The cars never run this well in the 15 yrs or so I've known the car.

I'll post more on the work that was done in another thread, but next days off I'll have to do another yet longer run to see how accurate that figure is.  After all, rarely would you get consumption figures better than the factory spec which is 13L/100km.

[Denis]

Hi mb350

Do you have the original owner's manual ? there is a very interesting graphic that shows factory-claimerd fuel consumption versus speed for a 280SE,350SE and 450SE.

It shows that 10.8l/100 is possible but at low speeds only...it also shows that if ou like cruising at 195kph with a 280SE, buy a 350SE if you want to use LESS fuels at that speed 

Denis

Paris, France

[oscar]

Thanks Denis,

I only got hold of the original manual and maintenance booklet last year after i thought it had been lost forever.  The best news is that I now have the car's data card.

My original manual only has a small paragraph about consumption and says to check out "technical data" where it then says avg 13L/100km travelling at 110km/hr.

However, I have another manual from a 78 450sel and on pg 43 that paragraph has expanded on fuel consumption and it has the 2 graphs.  It seems my figure may indeed be obtainable afterall.  It was interesting to read that "very low ambient temperatures" will lead to an increase in fuel consumption.  Remember it was over 40oC / 104F that day. Why do people bother with intercoolers and cold air intakes?  I think "very" is the keyword.  How low is "very low"?

I haven't had the chance to go for a long run so at the moment I'm doing an "around town" calculation.  BTW it's hit 40oC and over for the last 4 days.  Without the A/C working, I'm not going anywhere in a hurry.
 

[Mforcer]

After a drive through the country over the weekend, my 450SE has travelled 530km on the same tank and has still not needed to stop at a fuel station. That drive involved mostly cruising at 110km/h but also some city driving and all while the air conditioning was running. I'm happy with that 

I was talking to a friend while away who has a 10 year old 4.6L petrol Range Rover and was told that the Range Rover would get about the same milage as my 30 year old car.

[Mforcer]

Following up on my last post, I filled up with 94.66 L of fuel after driving 555 km. That needs to be some kind of record (without running out of fuel!) The milage isn't as good as your 680 km but I think I need to spend less time in the city.

[s class]

In my 280SE I once had the fuel level so low that I spluttered into the service station.  I realised that a record may be on the cards so I got the petrol attendant (we still have them in South Africa) to really squeeze it in.  I got over 100l.  And since I didn't think anyone would believe me, I got a print out slip from the pump management system.  When I find it I'll scan it in and post it here. 

I was excited as in 10 years of ownership its the only time I managed this.  I came annoyingly close a number of times - you know 95 or 96l or so. 

I know the tank is 96l, but I figured the extra must be going into the filler pipe.

Ryan in South Africa