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My wife has a standard "E" reg 1000cc mini, we used to use 4 star and since its demise have used LRP, but I have been told that I should be able to use ordinary unleaded petrol. Is this correct?
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gordon comley wrote:
>
> My wife has a standard "E" reg 1000cc mini, we used to use 4
> star and since its demise have used LRP, but I have been told
> that I should be able to use ordinary unleaded petrol. Is
> this correct?
There was a massive study on unleaded in A - series engines. Rover donated a load of them to a big oil company. I can't remember the exact results but I think most were Ok but those run above 4000 revs for long periods suffered extra wear and tear.
Dunno what rover recomend but even if you can't run a mini 1000 on unleaded alternating a leaded tankfull with an unleaded tankfull should be ok.
I ran an '89 Skoda Estelle (push rod engine similar to the A series - leaded only) on *unleaded* only for 5 years and 45,000 miles and it seemed fine. Scrapped it when I got bored with it - it was still in great nick - shame I couldn't give it away.
You need Dave Lacey for the definitive answer.
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In the good old days when leaded fuel was leaded and not this LRP stuff you could get away with running an A series on 2-3 tanks of unleaded then a tank of leaded to restore the lead protection to the valve seats. LRP does not work in the same way. If your mini can run on unleaded there will be a sticker on the slam panel of the bonnet with a green petrol pump together with the minimum octane level it will run on. It is unlikely that an E reg mini will be suitable for continual use on unleaded. Best advice is to have the engine tuned and run it on ordinary unleaded with a quality additive.
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What are these additives.Ive read that most do not work.
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Alan,
The Federation of British Historic Vehicle Clubs comissioned a series of tests at MIRA, using Rover A Series engines, and approved four liquid additives as providing good valve seat protection. They later added a couple more. Look for the FBHVC approved logo on a product. Castrol Valvemaster, Vlavemaster Plus, Superblend 2000, and Millers VSP were the original approved products - can't recall the additons.
Regards, Adam
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interesting that you say leaded fuel deposits lead back on the valve seats and prevents them from burning out, I used to think that too, but I recently read an article which claims that unleaded fuel damages "unmodified" valve seats because it burns at a higher temperature. The lead in leaded fuel, causes the fuel to burn at a lower temperature and is hence kinder to valve seats. Has anyone else heard the same version?
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I was under the impression that the lead in petrol provided a lubricant for the valves and put a coating on the valves and seats to provide a cushioning effect between them. Without the lead, and on engines with soft valve seats, the valves would wear the seats down regress into the cylinder head and reduce the valve tappet clearance. Eventually the valves wouldn't close properly and would burn.
I don't know if the combustion temperature of unleaded itself is any higher than leaded fuel but along the same lines I do remember reading, when unleaded first came out, the fire service saying that it was harder to put out vehicle fires fuelled by unleaded than it was leaded. The reasoning behind that I can't remember.
Regards
Adrian
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Adrian wrote:
>
> I was under the impression that the lead in petrol provided a
> lubricant for the valves and put a coating on the valves and
> seats to provide a cushioning effect between them. Without
> the lead, and on engines with soft valve seats, the valves
> would wear the seats down regress into the cylinder head and
> reduce the valve tappet clearance. Eventually the valves
> wouldn't close properly and would burn.
Lead protected valve seats by sacrifice, not lubrication.
The valves get hot, small "microwelds" occur between the valve
and the valve seat as the valve closes. The valve then opens, the
welds are broken and erosion occurs.
With unhardened valve seats, and leaded/LRP the erosion happens
to the soft layer of lead/additive, which is renewed whenever the
engine runs on leaded/LRP.
After extended use of unleaded petrol, the layer disappears and the
welds occur between the bare material of the valve and valve seat.
In the same car which is using leaded petrol, a layer of lead
is formed on the valve seat - this soft layer gets eroded, but
it doesn't matter since this layer is continually replaced.
The protective layer doesn't disappear with the first use of unleaded
and that's why a policy of 4 unleaded tanks for every leaded/LRP
combined with "don't thrash the engine" is a good idea for an older
non-performance engine.
/John
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John,
LRP is NOT the same as leaded in this respect, and affords no "memory" protection to valve seats. The option is to seek out one of the relatively rare outlets still selling genuine leaded fuel for your "one in four" fill, or use LPR the whole time, or use unleaded with a valve seat protecting additive (see earlier reply).
regards, Adam.
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