Classic cars forum & vehicle restoration.

colwyn500 · Joined: 21 Oct 2012 Posts: 1745 Location: Nairn, Scotland

Yesterday, when struggling to remove the "grandad-proof" cap on the expensive stuff I stick in the petrol tank on each fill, I ended up covered in the liquid.
It looks, feels and really smells like red diesel. Rhetorical question, "Am I being conned?"
More to the point, what is actually in lead replacement additive and how does it work?

Peter_L

Mog · Joined: 30 Dec 2007 Posts: 663 Location: Sydney

I only used to put additive in my 6 cly. Ford if I was going on a longer trip, say 100 miles or more. Just driving around locally, it never got that hot/warm. I was told you could put automatic oil [fluid ] in for the same effect.

Dipster

Bitumen Boy · Posted: Sat May 02, 2015 9:13 am Post subject:

I think it probably is a con. I used one of the main brands of lead replacement additive, endorsed by the FBHVC, for years without problems, but then problems developed lower down in the engine and it was rebuild time. Now the car could still move about under its own power - only just - so to avoid having it "blocking" the garage for ages I found a spare engine in the next valley, and set about rebuilding that. Once I'd paid out for the rebore, regrind, pistons, bearings, gaskets etc there wasn't any spare cash for the top end. Now the valves were pretty bad, but they were just recoverable, with a bit of effort, so the head was reassembled, and the valves tested with paraffin before fitting back on to the engine. In my innocence I thought it would be fine if I just kept using the lead replacement additive... 4k miles later and I was removing the head again to be converted due to bad valves and seats. Essentially it seems that lead replacement additives "work" so long as the valves aren't disturbed, but as soon as the work hardened layer on old valves and seats is removed you might as well not bother. This does of course suggest that additives are useless under any circumstances, and I certainly wouldn't bother with another car - just accept that the head may need work at some future point.

ka · Joined: 03 Dec 2007 Posts: 600 Location: Orkney.

These are the advertised contents, but different manufacturers use different contents,
Methylcyclopentadienyl manganese tricarbonyl (MMT)
Ferrocene
Iron pentacarbonyl
Toluene
Trimethylpentane (isooctane)
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KA

Better three than four.

Mog · Joined: 30 Dec 2007 Posts: 663 Location: Sydney

My older brother worked for Shell for many years. He said that the Shell "boffins " thought that shots of Redex was a waste of time, as they just got burnt up. Before they got to the cylinder walls. But wait a minute , what a bout a two stroke petrol engine ? The oil does get to the cylinder walls...

Dipster · Posted: Mon May 04, 2015 7:18 am Post subject:

As Shell did not manufacture Redex I can easily imagine why they might discount any worth it might have. I just saw it as an extra income at the pump! And the dispenser "gun" as just something else to keep clean. They were always slightly oily and thus attracted forecourt dust.

I have no idea whether Redex actually worked.

peter scott · Joined: 18 Dec 2007 Posts: 7214 Location: Edinburgh

Mog · Joined: 30 Dec 2007 Posts: 663 Location: Sydney

My brother and Shell were always ready to knock any other petrol / oil company.

ka · Joined: 03 Dec 2007 Posts: 600 Location: Orkney.

Two strokes induct via the crankcase, so the oil content in the pre-mix solution would coat the cylinder sides and big/little ends. Later oil injected two strokes fed the main bearing and was 'washed' off by the fuel/air mixture to provide lubrication to little end and cylinder sides before transfer to combustion chamber then the big bang.
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KA

Better three than four.

goneps · Posted: Tue May 05, 2015 7:01 am Post subject:

In other words, two-strokes were lubricated by a 20:1 mixture of petroil and luck.

MikeEdwards · Joined: 25 May 2011 Posts: 2705 Location: South Cheshire

I've got some "additive" but I rarely use it. I've been of the opinion that I don't do much mileage, little of it is on long motorway runs, at the limit my engine is turning over at around 3200rpm so not exactly 'fast', and I seem to have got away with it for about 15 years so far. Keeping in mind that the part of the head that will erode is the part that would be replaced if I were to have it "converted", I figured I'd have that done after it's eroded and I can't adjust the tappets any more, not just in case it does.

I should clarify I'm not claiming any specialist knowledge there, but I have been pleased to hear that people I think do have such knowledge seem to have the same thought.

Ray White · Joined: 02 Dec 2014 Posts: 7106 Location: Derby

baconsdozen · Joined: 03 Dec 2007 Posts: 1119 Location: Under the car.

I've used two stroke oil as an additive in my ex london taxi for years. I've tested before and after lots of times and it reduces knock and the engine is smoother and quieter. I doubt it lubricates the bores at all but apparently modifies the burn of the diesel fuel.
The only slight problem is some cheap brands seem to form a residue that settles in the base of the tank.
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Thirty years selling imperial hand tools for old machinery(Now happily retired).