Unleaded fuel

[n/a]

Hi

I have a 69 SL280 bought in USA using leaded fuel. Does someone know it possible to use with 98 Unleaded fuel?

Thanks in advance
Alfonso

[mulrik]

Just use 95 unleaded and you'll be fine! Everybody does that.
BR,
Ulrik


'67 250 SL Papyrus White 113043-10-000023

[rwmastel]

Alfonso,

Hello and welcome to the Group.  Unleaded fuel is fine.  It's been discussed - you can use the Search link in the top-right corner of this screen to search the Forum for key words you are interested.

http://index.php?topic=1979+fuel
http://index.php?topic=1648+fuel
http://index.php?topic=879+fuel

Thanks,

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[philmas]

Hi!

New to this forum, I can see this topic has been discussed quite a few times before.
I was told by a mechanist that the issue with unleaded is not valve seat recession, but more likely related to sodium valves overheating.

Here in France we have to grades of unleaded fuel: one is called super95 (95 RON) also called "eurosuper";
The other is called super98(98RON), and features a variety of oxygenated components which role is to raise the octane index in the absence of lead.These would cause overheating.

What do you think?

[rwmastel]

quote:Originally posted by philmas

.... I can see this topic has been discussed quite a few times before.

Philmas,

Hello and welcome to the Forum.  Yes, it has been discussed at length and I don't recall anyone being concerned with sodium-filled valves overheating.  If I recall correctly, the exhaust valves are sodium-filled for the specific purpose of tolerating high temperatures.

Think of it this way, if the old leaded fuel had a high octane rating, and these lead-free fuels are including additives to achieve a similar high octane rating, then wouldn't these fuels of supposed similar octane ratings burn at similar tempratures, regardless of how the octane rating was achieved?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[mrfatboy]

Just this week my local gas station is now selling a new high octane fuel.  It's from VP Racing Fuel and called Street Blaze 100.  It's going to be $5 to $6 a gallon.  There are alot of high performance cars in the area.

I was wondering how that fuel would work in the 280sl.  There is no way I would use it for my everyday fuel because of the expense but it might be fun to try it if I knew it would hurt my engine.

[ja17]

Hello,

I believe the lead was added to the fuel as a lubricant for the engine. However Mercedes began using improved alloys in their valves and seats (mid fifties) long before most manufactures. Unleaded fuels present no problems.

In actuality sodium fill was used to help cool the exhaust valves. Mercedes acutally stopped using sodium filled valves in some modern "lead free" engines like the 380SL. I guess the aluminum block helped transfer heat away from the vales.

Joe Alexander
Blacklick, Ohio