Petrol engines before unleaded ie 1989

[DITTRICH]

Dear All
As a matter of interest, I would be curious to know...

1 What fuel is used for mercedes engines originally manufactured to work with leaded fuel?
2 What are the implications of using unleaded for these engines for prolonged periods? Is there anything that needs to be modified or replaced sooner than might otherwise be the case?
3 Does the introduction of catalytic converters in 1989-90 have anything to do with this? I thought that since catalytic converters don't like lead that there must be some link.

Regards

Les

 

[Shude]

If the car has no catalytic converter but has been manufactured to accept unleaded then you can use 4-star, unleaded and LRP in it with no problems. IIRC they used to suggest putting a tankful of 4-star in for every 5 unleaded fills or something.

I used to own a vauxhall astra which was from 1989 and it'd accept those three. It NEVER had any 4-star in it's life and I think that's what caused the engine problems it had, it NEVER started properly, not even when it was new although that was probably also due to the introduction of auto-chokes that year.

 

[Stratman]

Lead (in the form of tetraethyl lead) was originally put in petrol to increase its octane rating. This allowed higher compression ratios and hence better performance and efficiency. The lead then got deposited on the inner 'hot' surfaces of the combustion train (the white stuff on the inside of exhaust tailpipes on 'leaded' cars). This was found to have a cushioning effect on valve seats. It meant that they could be made from cast iron and still have a decent lifespan.

Without the lead to cushion the repeated impacts of the valve against seat they wore away very quickly. Remember Vauxhalls and Shell twenty or thirty years ago? To run with unleaded fuel, the valve seats are made from austenitic (I think!) iron. This, and a small retardation in ignition timing are the main differences.

If leaded fuel is put into a catalytic convertor equipped car and the engine is run, then the lead will very quickly coat the platinum in the cat and ruin it. By very quickly I mean a few seconds.


On a completely different note. Shude, could you take a look at this thread and have a gander at your wonderful parts machine?

 

[Shude]

On a completely different note. Shude, could you take a look at this thread and have a gander at your wonderful parts machine?

I did consider looking in the catalogue when I saw that thread

Anything that has a motor in it will cost a fortune brand new, be warned!

 

[PJH]

The engines would have been U/L compatable long before 1989.
U/L was introduced in other countries much earlier than in the UK.

 

[Stratman]

Anything that has a motor in it will cost a fortune brand new, be warned!

Gulp

Looks like the bodge-it-myself approach then.

 

[DITTRICH]

..thank you for the useful replies. The type of car I'm thinking about needs to be either diesel or petrol - which can run on leaded / unleaded fuel as it's going to be used in eastern europe - russia. Since diesel W124 estates are very rare and getting and lhd one from germany would be a pain, I'm widening my options...

1 Diesel estate W124 300D to 1996
2 Petrol estate W124 300E to 1989
3 Diesel estate W202 C250TD

Just got to pay the taxman this month and I'll start looking just after that.

Regards

Les

 

[PJH]

1988 E reg E250 on Exchange & Mart
A C250TD must be easier to find..........

 

[DITTRICH]

...thank you PJH...