Classic cars forum & vehicle restoration.

[layla]

i have a volvo 940, i get reasonable mpg but want to improve it, i have seen some additives in halfords and wanted to know what is the best and recomended. i noticed some octane additives contain injector cleaners do the work or can they block up the care/damage the car?

[RobMoore]

you will not get better mpg by adding additives of any sort. the only way to improve mpg is having the engine properly tuned and altering ones driving style.
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[Rick]

I agree, I think more time spent looking at driving style, checking tyre pressures etc would be beneficial. Injector cleaner may improve its running, but not sure you'd see any gains in mpg.

Welcome to the forum

Rick
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[layla]

thankyou, i wasnt sure i looked at the mecanical ones and reviews and they said they were rubbish. but found no reviews on the additives.
A friend tryed a fuel injector cleaner that you added but it moved some of the coke into another part of the engine effected its running

[Jim.Walker]

I have only ever come across one additive which I can honestly say worked. Except Redex which did soften carbon deposits making de-coking easier in the days when it was a frequent necessity.
The additive which worked was the fuel additive which homoginised(?) water in a fuel tank allowing it to pass through carburetter jets and injector systems without stopping the engine. Thus clearing the problem.
For the rest I would not waste my money.
Representatives used to perform demonstrations with impressive equipment to prove the worth of their additives. Careful thought normally revealed that the equipment produced bearing loads etc. many many times beyond those existing within any normal mechanical device.
Their claims were akin to proving that a 15" hawser was necessary to tow an ocean going ship and therefore the same was true to tow a rowing boat!
How many of the additive manufacturers offer a money back guarantee? And how would you prove your point anyway?
Save your money!
Jim.
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Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[peter scott]

[Jim.Walker]

I agree with you 100% Peter.
But you missed out engine braking down hills, which can save fuel AND brake linings.

However! In my taxiing days I remember picking up a driving instructor whose car was out of service. I drove him about ten miles as you outline, expecting perhaps some comment on sensible and safe driving.
But no! He said "Your driving is old fashioned. You do not use the brakes often enough and someone is going to run into the back of you." I pointed out that if anyone ran into the back of me while I was sensibly slowing down gently by using gears they should have been better taught. If only because they would be in the correct gear for picking up speed again. Not impressed he then told me I "overused" the gearbox which would wear out the clutch. I then confounded him by doing a few gearchanges without the clutch! The clutch on that Peugeot 405 did eventually wear out at over 200,000 miles - as a taxi.
He no doubt still teaches his pupils to drive on the brakes and if all driving instructors are the same some drivers will always continue to rush past me as I am easing up for a red light or junction etc.
I will continue to drive as I always have. In 55 years I have yet to be shunted from behind.
Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[peter scott]

Hi Jim,

Your engine braking is even more effective with today's fly by wire machines. Here's a plot I took from the OBD II port on my Mondeo TDCi
From time 13 through to 24 I took my foot off the accelerator and unlike cars in the past, it uses absolutely zero fuel on overrun. At time 24 I then took it out of gear and so the ECU determined that the engine would stall if it didn't start injecting fuel again. So for overruning nowadays don't freewheel just select your highest gear and run on as low a throttle as possible. (Fuel is in mg/stroke.)

Peter


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http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[Jim.Walker]

Very interesting Peter, but rather beyond the ken of my 72 years old brain.
My experience over a HUGE mileage is primarily of vehicles pre-engine management systems, though I realise what you are saying.
By the way, "coasting" did not come into my mind. I NEVER coast because in that huge mileage I have suffered four or five brake failures and possibly survived on at least two because I do not coast.
I don't know whether you are familiar with Cromford Hill in Derbyshire, but one was just starting to descend that with a Sheerline hearse of all things. Already in third, a quick engine boost and change down to second gear with a few clicks taken up on the handbrake allowed me to descend safely,
Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[peter scott]

[Jim.Walker]

A bit over 23000 acually Peter.
Cummings have used a (common rail) pressure/time system for over 40 years on their engines, though I don't think the pressures used to be that high. I'm a bit hazy now, but I'm pretty sure the timing was from extra lobes and rockers on the camshaft rather than "electrical trickery". I never actually worked on a Cummins engine or their equipment, Though I have overhauled calibrated and tested jerk pumps and injectors. In the proper environment and the proper equipment.
In any case modern "jerk" pumps can go up to more than that! In some cases up to 30,000!
Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[peter scott]

[Churchill Johnson]

I agree with using throttle and less braking god know's why everyone seem's to be in a hurry these day's to get nowhere! i think a lot is to do with the idiot's who advertise their car's on telly on how fast it can get round a bend and 0-60 time's and top speed and of course it must have plenty of horse power,and the idiot's who buy them thinking they can drive like that all the time , i run my old car in fifth gear at 30mph most times loaded with tool's this give's me over 40mpg mostly town driving as for driving so called instructor's i s--t them ever noticed how they drive when they have no pupil's on board of course they have passed a instructor's exam!!!!!!!!! so they know how to drive,this is a few thing,s i have noticed in the last week driver's do overtake a tractor single carriageway on crossed white line's that was a 8/whl tipper followed by a taxi,van turning up a one way road the wrong way,another tipper and car's in the r/h and straight over lane of a slip road turning left anyone in the left lane can also go straight over this would have resulted in an accident ,several car's turning right against a left turn only.

[peter scott]

Whilst reducing speed will improve your fuel economy you can still get respectable mpg and drive reasonably fast.

With the Mondeo TDCi used for the graphs above I recently did a trip of 1370 miles with a mix of motorway and A class roads mainly in the outside lane on the motorway and without creating any tail backs and at 60 mph on A class roads. Checking my fuel brim to brim I got 59.76 mpg overall for the total journey. This car is 15' 7" long and weighs 31 cwt.

Peter
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http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[Jim.Walker]

This post seems to have gone well off topic. Possibly my fault! But on the fuel consumption side. Almost everyone, even those who do not rush up to lights etc., seem to take off from junctions and traffic lights as if they are trying to remove Vettel's pole advantage.
Still, on the brighter side, the extra tax they pay may cure the Country's economic depression problem?
Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!