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E34 (1989 - 1995)

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  #1  
Old 02-11-2013, 06:38 AM
Bugsie Bugsie is offline
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Mein Auto: BMW E34 M50 2.5
Convert to unleaded

Hi all.

My car with M50B25 from 1990/06 is a leaded engine and now that this type of fuel is ended, how can I convert it to unleaded?

Thanks in advance for any input.

Cheers

Fernbando
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  #2  
Old 02-11-2013, 06:45 AM
snowsled7 snowsled7 is offline
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The engine has an aluminum head so it already has hardened valve seat surfaces. This is typiclly the major wear item on engines designed for leaded fuel. You should not have to do anything. Run a similar octane unleaded and the car will not know the difference.
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  #3  
Old 02-11-2013, 06:50 AM
cutter67 cutter67 is offline
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they say you learn something new everyday and that is true. i didnt realize that leaded fuel was still being used. the problem here in the states back when they phased out the leaded fuel was mostly the valve seats were too soft you had to have hardened seats installed in the engine. i cant believe BMW would make a different engine for leaded fuel but i really dont know.....this is very interesting
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Old 02-11-2013, 07:00 AM
snowsled7 snowsled7 is offline
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The difference is that most US manufacturers use a softer iron in the cast iron heads. I guess most pre-70's iron head engines would be like this. The lead provided lubrication that prevented the valves from recessing into the head.

Since cast aluminum of just about any type is softer than cast iron, all aluminum heads require hardend seats. If it has an aluminum head, which all M50's do, it can safely run unleaded.

Now there may be a specific leaded tune but I doubt it. The engine really can not tell the difference, just run a similar octane for similar performance as mentioned.
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  #5  
Old 02-11-2013, 08:53 PM
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BMWFatherFigure BMWFatherFigure is offline
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+1 on above. Also the valve recession is only a major problem on engines working at high loads / full throttle for extended periods.
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  #6  
Old 02-12-2013, 01:56 AM
Bugsie Bugsie is offline
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Hi everybody.

Thanks for the prompt answer. Always useful.

In that case I'll just do nothing. I'm running 98 unleaded, so it will keep "eating" that

Thanks again for all the help

Cheers

Fernando
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  #7  
Old 02-12-2013, 05:44 AM
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BMWFatherFigure BMWFatherFigure is offline
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Ah - 98. BMW's friend.
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Current:
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  #8  
Old 02-12-2013, 07:22 AM
Bugsie Bugsie is offline
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I changed from 95 to 95 and, don't know if it's suggestion, but the car got better and better. And if he runs!!!
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  #9  
Old 02-13-2013, 12:16 AM
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BMWFatherFigure BMWFatherFigure is offline
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I run 98 all the time in all my fleet (6 mixed). No complaints. 91 or less is for chain saws and lawn mowers.
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Current:
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Previous:
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  #10  
Old 02-14-2013, 03:20 PM
Bugsie Bugsie is offline
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Hi,

In here only 95 and 98. i started with 95 but quite quickly changed to 98

Cheers

Fernando
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