Is it worth trying a petrol additive?

[markjay]

Speet-Tec isn't an octane booster, this has been made clear from the start! So could it contain a chemical that v-power doesn't or a higher amount..... that would be an aid to providing a better flame front or burn.......possibly? I think this is why their claim is basically just mid range acceleration especially under partial load. At WOT the combustion chamber should seriously be vaporising anything anyway hence why there's probably no power gain there

Yes W169 has an oil tempreature sensor, can be accessed by the service menu by having the main display set to odometer on accessories key position then pushing trip reset three times before going for ignition. Will also allow access to the literal service/maintenance logs, an option to disable ABS/ESP/CBC/TPMS all of it for rolling road testing. Sadly that's the only way to turn the ESP off on a W169 and the vehicle is then speed restricted to about 70MPH. Some other stuff there too, what engine code you have and it's ECU/Control unit firmware revisions. I heard something about Mercedes refusing to use some kind of oil sensor before, but not sure what one. Are they not funny about deadlocks too?

As for what oil additives they recommend, they don't, they will usually tell you never to use any additives unless it's for a specific climate or for a designated market where the fuel may be different, and it will be one of THEIR additives. Liqui Moly is good, but ever seen Lucas Heavy Duty Oil stabiliser? that stuff is REVERED by some people and you can watch youtube videos of actual real demonstrations on lawnmower engines etc, that stuff literally stays on stuff like slime and really minimises wear.

People are always ready to jump on the word additive because they assumed that all those thousands of hours of bench testing the manufacturer must be 100% correct in everything and nothing could improve on the consumables they tell you to use, but its not true. Especially if your engine is old, tired or dirty. My Mercedes is 11 years old, some people on here will have older ones. Oil tech has moved on in that time and there COULD be something that causes less wear, heat and friction available that would benefit and old tired motor. I used to use 0w20 in my Honda D series, an engine Honda said 20 years ago needed 5w30. Ran way, way better on the 0w20

It's a difficult one. It's like advertising that compares a product to 'other popular brands'.

Again, I don't deny the benefits of their product, but they do not specify to which type of fuel these apply.

So while I don't think they are lying as such, unless they state exactly what benefits they product will bring to cars already using premium fuels, I remain unconvinced.

 

[SpikyMikey]

I always used Millars fuel additive in my vans; these were simple(ish) 2.5TDis with cats but no DPF malarky.
Most did up to 2-250K miles before I got shot of them and I never once had an issue with injectors, fuel pumps or the like. The ones I kept long enough to need MOTs always flew through with emissions results way under the max allowed. Whether the additive made a difference or whether it was the fact that I rarely did short journeys and always had 10,000 mile oil changes of course is pure conjecture.

 

[PunkyB]

Yeah I do believe in some additives, I will tell you now Lucas stop slip has kept the knackered autobox in my mums/family old hyundai for years now. Yes there are dangers of increasing oil viscosity too much or too little.

But just as you say if something works for me and I'm happy to pay for it then that's just fine. My W169 is 11 years old (12 if you go by production date), it's a CAT C Write off and they are hard as hell to maintain and work on. So to be honest it's not like you care too much about the long term effects of a particular oil additive, if the timing chain is quiet for now then good, because eventually its next stop will likely be the scrapyard

The dinosaur thing was a joke BTW was thinking that petrol distilled from crushed T-Rexes came out as V-Power Its just people will always argue it seems about fuels, oils and additives

I guess we CAN all at least agree on one thing, compared to the US and other countries we are pretty lucky with our fuel standards, legal requirements/Industrial standards and 95 RON being the cheap option. In America (though it varies state to state) 85-87 is regular , 89 is mid level and 91-93 Octane is like their super unleaded. And we used to laugh about the pathetic power for their huge motors when the poor bloody things had to run such retarded timing.

 

[Bellow]

I guess we CAN all at least agree on one thing, compared to the US and other countries we are pretty lucky with our fuel standards, legal requirements/Industrial standards and 95 RON being the cheap option. In America (though it varies state to state) 85-87 is regular , 89 is mid level and 91-93 Octane is like their super unleaded. And we used to laugh about the pathetic power for their huge motors when the poor bloody things had to run such retarded timing.

It's measured differently in the USA - that's why its numbers are different.

 

[markjay]

It's measured differently in the USA - that's why its numbers are different.

Indeed.

Google "RON vs MON octane".

 

[Larkone]

Isn't there a strong element of expectation bias here - I paid for something so I will defend it's efficacy without any empirical evidence. Very common problem in hifi, especially with cables

 

[Bellow]

Indeed.

Google "RON vs MON octane".

(RON + MON)/2 in the USA.

 

[GeeJayW]

It's measured differently in the USA - that's why its numbers are different.

Indeed.

Google "RON vs MON octane".

Octane is 'measured' in the same way in the UK and in the USA. In fact the measurement process is pretty much universal as far as I know. That said, I think that octane quality is typically calculated/modelled based on batch formulation and GC analysis with samples taken for octane measurement less frequently in line with QA statistical recomendations.

Research Octane Number (RON) is measured using a (low speed) single cylinder CFR engine
Motor Octane Number (MON) is measured using cars on a chassis dynamometer
The difference between the two number is called Sensitivity. EN:228 implies a maximum Sensitivity of 10 octane numbers for regular gasoline (RON 95, MON 85).

Mabanaft Limited. All rights reserved. - Unleaded Petrol

www.mabanaft.co.uk

On the pump we see:
In the USA they refer to the octane quality of a fuel using a term called Anti-Knock Index (AKI) which is (RON+MON)/2
So, 90 (AKI) octane in the USA approximates to a 95 RON fuel from the UK and Europe

In the UK we only refer to RON for octane quality.

There is more to base fuel quality than the octane number. In the UK we typically have very good quality base fuel in our forecourts. However, this is not the case everywhere.

 

[Bellow]

Isn't there a strong element of expectation bias here - I paid for something so I will defend it's efficacy without any empirical evidence. Very common problem in hifi, especially with cables

Yep, not forgetting the 'butt dyno'. ''I could feel the extra acceleration through the seat of my pants''. Sure you could - because your wallet is thinner now.

 

[GeeJayW]

Yep, not forgetting the 'butt dyno'. ''I could feel the extra acceleration through the seat of my pants''. Sure you could - because your wallet is thinner now.

There is an element of that, but I have done blind tests on track where the driver was asked to comment on vehicle performance while we swapped fuels around. It was remarkable how good some drivers are at picking up differences and how well their comments stack up against GPS and engine data gathered at the same time. That said, we also had drivers where we gave them a 10% benefit in acceleration and they couldn't tell...

 

[Bellow]

Octane is 'measured' in the same way in the UK and in the USA. In fact the measurement process is pretty much universal as far as I know.

You are right. I should have said presented (at the pumps) differently.
I run an American motor and until I found out that in the USA the octane rating is presented differently I was struggling to get my head around how a 102mm bore, offset (not central) spark plug, 9.4:1 compression ratio motor could survive with the handbook recommended 87 fuel.

 

[Bellow]

There is an element of that, but I have done blind tests on track where the driver was asked to comment on vehicle performance while we swapped fuels around. It was remarkable how good some drivers are at picking up differences and how well their comments stack up against GPS and engine data gathered at the same time. That said, we also had drivers where we gave them a 10% benefit in acceleration and they couldn't tell...

Isn't it said that a drop in power is more likely to be noticed than an increase?

 

[GeeJayW]

Isn't it said that a drop in power is more likely to be noticed than an increase?

Yes I'd say that is the case, especially where drivers have become used to a certain level of performance. Small incremental increases are less easy to pick up on.

Interestingly, when we did some survey stuff, we found that a lot of drivers never actually use the full performance of the car anyway and so never really take advantage of any performance benefits the come from the fuel.

The part-load stuff that @PunkyB is alluding to, is an interesting area that can definitely be affected by base fuel formulation. Liqui-Moly have this to say about their product:

"This highly modern fuel additive was specially developed to noticeably improve acceleration and throttle response under partial load. Provides more driving pleasure through optimized performance yield. The engine starts better and even runs more smoothly"

At £10 a tankful, I'd hope it would give some measurable benefits. All I'm seeing in their blurb is marketing speak. At 0.35% concentration in the fuel though... If some can tell the difference, good for them. I'm unconvinced and will keep the tenner for some more tangible like a few pints of beer.

 

[Bellow]

Yes I'd say that is the case, especially where drivers have become used to a certain level of performance. Small incremental increases are less easy to pick up on.

As you say, familiarity plays a large part. Looking for the same (and not getting it!) is a different mind-set to looking for improvement...

Interestingly, when we did some survey stuff, we found that a lot of drivers never actually use the full performance of the car anyway and so never really take advantage of any performance benefits the come from the fuel.

But they do - in a way (more anon) - but when it comes to wringing its neck to the red line, agreed, uncommon.

The part-load stuff that @PunkyB is alluding to, is an interesting area that can definitely be affected by base fuel formulation. Liqui-Moly have this to say about their product:

If they truly mean part load ie, the engine experiences real throttling then the reduced air flow and turbulence might be a regime where smaller droplet size helps.
But - and this is a point people seem to struggle with - half throttle is full throttle at half the rpm of maximum power. That isn't exact as torque curves are never truly 'flat' but it highlights the concept well enough to be understood.
So, accelerating with the throttle plate half way open from say, 1500 to 3000 rpm (on a 6000rpm motor) full torque can be developed over that rpm range and not impeded until 3000rpm is reached. Drivers might not (rightly) believe they are exploiting all of the available hp but they are exploiting all the available torque in that speed range (and maximum torque too if it arrives at below 3000 rpm and doesn't rely on eg, extra enrichment brought about by greater pedal travel). Only at 3000 rpm and beyond will the half open/closed butterfly impede airflow to justify the term 'part load'.
This is the operating range that catches out too low an octane rating (though I did well to keep out of the recent threads on the topic!) much more than high rpm (where there is less time for detonation anyway).

"This highly modern fuel additive was specially developed to noticeably improve acceleration and throttle response under partial load. Provides more driving pleasure through optimized performance yield. The engine starts better and even runs more smoothly"

At £10 a tankful, I'd hope it would give some measurable benefits. All I'm seeing in their blurb is marketing speak. At 0.35% concentration in the fuel though... If some can tell the difference, good for them. I'm unconvinced and will keep the tenner for some more tangible like a few pints of beer.

There isn't enough 'tech' there to convince me and droplet size is more nuanced having to be sufficient to afford it inertia to travel into the heart of the airstream (not just a localised 'stratified' pocket) but not so small as to get trapped in the crevice volumes (eg, above rings, behind valve margins). If a splash of additive is all it takes then I have to wonder why after 50 years of trying (with varying degrees but not complete success) this isn't the solution to the problem of poor atomisation encountered in direct injection 2-stroke engines.

I'm not totally against fuel additives. The cleaning effect for fuels lacking in detergency is well worth having but (as with lubricants) it is as a preventative not remedial measure. Anyway, the last thing I have to concern myself with is droplet size. My LPG arrives at the inlet valves already fully gaseous....

 

[GeeJayW]

As you say, familiarity plays a large part. Looking for the same (and not getting it!) is a different mind-set to looking for improvement...





But they do - in a way (more anon) - but when it comes to wringing its neck to the red line, agreed, uncommon.




If they truly mean part load ie, the engine experiences real throttling then the reduced air flow and turbulence might be a regime where smaller droplet size helps.
But - and this is a point people seem to struggle with - half throttle is full throttle at half the rpm of maximum power. That isn't exact as torque curves are never truly 'flat' but it highlights the concept well enough to be understood.
So, accelerating with the throttle plate half way open from say, 1500 to 3000 rpm (on a 6000rpm motor) full torque can be developed over that rpm range and not impeded until 3000rpm is reached. Drivers might not (rightly) believe they are exploiting all of the available hp but they are exploiting all the available torque in that speed range (and maximum torque too if it arrives at below 3000 rpm and doesn't rely on eg, extra enrichment brought about by greater pedal travel). Only at 3000 rpm and beyond will the half open/closed butterfly impede airflow to justify the term 'part load'.
This is the operating range that catches out too low an octane rating (though I did well to keep out of the recent threads on the topic!) much more than high rpm (where there is less time for detonation anyway).




There isn't enough 'tech' there to convince me and droplet size is more nuanced having to be sufficient to afford it inertia to travel into the heart of the airstream (not just a localised 'stratified' pocket) but not so small as to get trapped in the crevice volumes (eg, above rings, behind valve margins). If a splash of additive is all it takes then I have to wonder why after 50 years of trying (with varying degrees but not complete success) this isn't the solution to the problem of poor atomisation encountered in direct injection 2-stroke engines.

I'm not totally against fuel additives. The cleaning effect for fuels lacking in detergency is well worth having but (as with lubricants) it is as a preventative not remedial measure. Anyway, the last thing I have to concern myself with is droplet size. My LPG arrives at the inlet valves already fully gaseous....

Intake valve deposits are often made up of VI improver that makes it’s way into the intake system via the blowby gases. Gaseous LPG and air aren’t badly impeded by deposits unless they are really bad. Liquid fuels however can get held up (leading to lean combustion) or ‘dribble’ into the cylinder in large drops which isn’t helpful for mixture preparation.

 

[Bellow]

Intake valve deposits are often made up of VI improver that makes it’s way into the intake system via the blowby gases. Gaseous LPG and air aren’t badly impeded by deposits unless they are really bad. Liquid fuels however can get held up (leading to lean combustion) or ‘dribble’ into the cylinder in large drops which isn’t helpful for mixture preparation.

I've heard about that - the carbon can almost soak up the liquid fuel before releasing it again. That really would screw up mixture formation.
I am actually using a fuel additive. It's designed/formulated to be added to petrol in the tank but I have it in a 'valve saver' system and is fed to the inlet manifold at the throttle body so it has to pass the inlet valves on the way to the cylinder. This is preventative to give some lubrication to the valve guides and seats and to keep the valves clean from anything coming up from the crankcase.

The 'valve saver' system has its own fluid but nothing in the way of explanation of how it survives combustion to supposedly protect the exhaust valves so I've dispensed with it in favour of my fuel additive. All I have ever seen about valve saver fluid formulations is that they do contain elements that can survive combustion - the same elements that poison cats... My engine is designed for unleaded fuel so I'm not seeing the need to protect the exhaust valves - only the inlets which would otherwise be dry. I've also made efforts to maximise combustion speed (short of actual timing adjustments) so that the fuel (LPG) is burned as early in the cycle as possible to avoid subjecting the exhaust valves to unnecessary heat. That is considered a good strategy for LPG motors to protect exhaust valves. My engine was also available as an LPG/CNG/gasoline engine and I doubt that the valve or seat materials were different. I reckon I have everything covered - unless you see a flaw?

 

[GeeJayW]

I've heard about that - the carbon can almost soak up the liquid fuel before releasing it again. That really would screw up mixture formation.
I am actually using a fuel additive. It's designed/formulated to be added to petrol in the tank but I have it in a 'valve saver' system and is fed to the inlet manifold at the throttle body so it has to pass the inlet valves on the way to the cylinder. This is preventative to give some lubrication to the valve guides and seats and to keep the valves clean from anything coming up from the crankcase.

The 'valve saver' system has its own fluid but nothing in the way of explanation of how it survives combustion to supposedly protect the exhaust valves so I've dispensed with it in favour of my fuel additive. All I have ever seen about valve saver fluid formulations is that they do contain elements that can survive combustion - the same elements that poison cats... My engine is designed for unleaded fuel so I'm not seeing the need to protect the exhaust valves - only the inlets which would otherwise be dry. I've also made efforts to maximise combustion speed (short of actual timing adjustments) so that the fuel (LPG) is burned as early in the cycle as possible to avoid subjecting the exhaust valves to unnecessary heat. That is considered a good strategy for LPG motors to protect exhaust valves. My engine was also available as an LPG/CNG/gasoline engine and I doubt that the valve or seat materials were different. I reckon I have everything covered - unless you see a flaw?

Exhaust valve cleanliness is generally less of an issue than inlet valves. I’d certainly be wary of putting anything in that had potential to damage the catalyst in the hope that it did something useful for the valves.

I don’t have much experience of LPG applications beyond a catalyst durability programme that we did on a consultative basis a number of years ago, so I can’t really add to your current thinking on that. Wish I could.

 

[Bellow]

Exhaust valve cleanliness is generally less of an issue than inlet valves. I’d certainly be wary of putting anything in that had potential to damage the catalyst in the hope that it did something useful for the valves.

This is what I found:

''the idea being like lead introduce a soft metal type molecule that when combusted forms it's oxide which then adheres a bit and forms a soft metal like cushion on the valves which can then be further covered with carbon etc. They use compounds of potassium, manganese and sodium.''

I'm sticking with my petrol additive. Not least as it is made be the same company that makes my engine oil so no danger of any chemical clashes there.

I don’t have much experience of LPG applications beyond a catalyst durability programme that we did on a consultative basis a number of years ago, so I can’t really add to your current thinking on that. Wish I could.

Anything to say re LPG and cat durability? What always takes me by surprise is how much water is present in the exhaust with LPG. During its first MOT in my ownership it was sat idling for a while during steering and brake checks and when the tester gave it a bit of throttle water emerged from the tail pipes like they were hoses!

 

[GeeJayW]

This is what I found:

''the idea being like lead introduce a soft metal type molecule that when combusted forms it's oxide which then adheres a bit and forms a soft metal like cushion on the valves which can then be further covered with carbon etc. They use compounds of potassium, manganese and sodium.''

I'm sticking with my petrol additive. Not least as it is made be the same company that makes my engine oil so no danger of any chemical clashes there.

Anything to say re LPG and cat durability? What always takes me by surprise is how much water is present in the exhaust with LPG. During its first MOT in my ownership it was sat idling for a while during steering and brake checks and when the tester gave it a bit of throttle water emerged from the tail pipes like they were hoses!

Putting metallic compounds in with the fuel is not typically a good idea for applications that have exhaust after treatment systems.

We had no cat durability issues during the LPG programme we ran.

 

[Jetbags]

You echo my thoughts on what the root cause is. I’m not so convinced about your solution. 100 miles a month would cost over £200 a year in petrol alone, as well as the cost of wear and tear on tyres, brakes, suspension. I’m only thinking of a £10 dose of additive once, then perhaps once a year to keep carbon build up at bay if it works.

Feeling a scottish vibe coming through here....