Unleaded and Leaded

[nsehmi]

Hi all,

I know this topic is a very popular one and I have trawled through past posts to see if what I need is there, but no luck so far...

...so, anyway, I open my fuel cap and it says on that side that Unleaded or Leaded fuel is acceptable...how is this poss? and for such a case is there an optimum fuel which I could/should be using?

 

[jberks]

Hi,
Id guess that the engine is ok without the lead as a lubricant, but there is no cat so leaded is also ok.
What is the car ?

 

[nsehmi]

Hi jberks,

The Car is 190E 2.0ltr Auto (W201 I think)...my primitive understanding was that the lead in leaded fuel would coat and protect but would poison the catalyst on a cat converter; unleaded fuel obviously can't do this so components are hardened so as to not require a coating...

...if this is basically right, how is it that the engine can cope with both fuels? Would using leaded, or a lead additive be in anyway advantageous? or detrimental in the long term?

 

[mlc]

Hi,

The earlier answer by jberks got it right. You dont say how old the car is and I dont know the model, but I guess it is 80's and i'm sure it hasnt got a cat.

Lead was added to petrol from about the 1st world war as a lubricant and to enhance the octane rating. It was removed when people realised it was harmful, especially to children.

The US and Japan were the first to see the light, so cars for those two markets became capable of running without lead in the 70's. These cars are capable of running on lead or unleaded. Europe was slower on the uptake, so lots of cars from the 80's from say BL (Rover) still needed leaded fuel. It wasn't until cats were fitted that unleaded had to be used.

Bottom line is, if its says either it can use either. You should use unleaded because it will be set for the lower octane - higher octane will provide no advantage and cost you more.

I hope this helps. You're right that this topic is heavily covered but we still never all agree on the age of the first MB's that can use unleaded!

Mark

 

[nsehmi]

Thanks for clearing that up guys. The car is from 1991...basically I'll stick to Unleaded and not think about experiementing with different fuels...

...although..and this should probably be a separate post..I started the car up one morning and it started making a loud 'ticking' sound which increased in line with acceleration...on describing it to my dad he thought it might be the exhaust manifold...this continued for a few days till I filled it up with 'Shell Optimax(?) Unleaded fuel' and it hasn't made a sound since...are the two related or coincidence?

 

[mlc]

Im sure the guys from Shell would claim this as all their own work! Dad could be right, but lots of other things sound like ticking. If it does it again you need to get a friendly mechanic to listen. I think that the fuel type is not relevant, different fuels shouldnt have an instant effect.

Good luck with the car.

Mark