Will 1998 740iL run on 10% ethanol blend?

LIVING ON ROUTE 66

MEMBER
1998 BMW 740

I have a great opportunity to purchase a cherry one-owner 1998 740iL with 45,000 miles on it. The manual says it needs 91 octane. I have two questions:

Do I really need to run 91 octane? My Pathfinder runs great on an 89-octane 10% ethanol blend.

Whether I run 89 or 91, will I see a reduction in performance or smoothness with these blends?

Thanks!

2 Replies

DOCHAGERTY

MECHANIC
9,601 POSTS

What a great question! To start with, I would say the only issue that would cause concern would be the fuel compatibility with the flexible lines. Here in California, the petroleum industry has(or had) been adding an "oxidizing" component to our fuel to reduce emissions for years. As far as will the car run on fuel rated at less than 91, my response is from experience that these cars will run on any fuel that pathfinder will run on. Performance may well be affected, and deposits might be an issue. If it were mine, I would try it. What have you got to lose?
BTW send me a PM and lets talk about your possible future purchase of this 740, there are some items you may wish to be made aware of.

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Tuesday, November 20th, 2007 AT 5:03 PM

SQUABBIT

MEMBER
5 POSTS

BMW AG recommends a minimum of 91 octane fuel and I've found that when I use 89 or 87 octane fuel that performance suffers greatly. So I suppose it's a crap shoot. Overall my impression is that less than 89 octane will damage engine componentes over time. But this is one man's opinion! What I do is switch octane ratings with 91 octane every third tank of fuel.

Also according to BMW AG 10% ethanol will not harm the vehicle, but they didn't say anything about MBTE and other additives.

Hmmm, what's up with that?

John

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Tuesday, May 11th, 2010 AT 11:28 AM

Will 1998 740iL run on 10% ethanol blend?

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