re: Leaded vs Unleaded Fuel???

[Bill Matthews <bmatthws@xxxxxxxxxxxxxxxx>]

Eugene,

Is .my Malaysia ? In NA we haven't had leaded fuel for years ! To try
and help answer some of your questions some of which seem to come up
continually on all the auto lists and boards...


> Date: Fri, 30 Oct 1998 12:14:30 +0800
> From: "Eugene Hoe" <eugene@domain.elided>
> Subject: Leaded vs Unleaded Fuel???
> 
> Just wondering if anyone knows the effects of using leaded vs unleaded fuel
> in an E34 525i M20 90.
> I know the M20 can take both leaded vs unleaded. Anyone can enlighten me
> with the effect of using
> either fuel in terms of :
> 
> 1) Performance, leaded fuel or unleaded fuel will be more powerful??

There is no inherent difference in power levels between leaded and
unleaded fuels. Lead was (still is in some countries) added as an
anti-knock additive i.e. it increases octane level. Octane is not a
measure of power, it is a measure of a gasoline's ability to resist
pre-detonation under a certain set of test conditions.

> 2) Long term affects, more engine wear , etc (heard leaded fuel has a
> natural lubrication to it)

Tetraethyl and Metraethyl lead contain low levels of halogenated
bromides to help scavenge the lead out of the combustion chamber. These
additives provide lubrication to the valve seats, particularly the
exhaust valve (the valves rotate as they seat). Almost all cars
manufactured since the mid 70's have hardened valve seats so that this
is not a problem. For most cars manufactured before then it isn't a
problem or if it is you have hardened seats put in on your next valve
job.

> 3) Noiser engine... (did notice unleaded fuel causes the engine to be noiser
> or is it my imagination)

Imagination

> 4) Anything else ......

Lead in gas is one reason for fouled spark plugs, unleaded gas lets you
get more miles on your plugs and all other things being equal (i.e. the
gas has proper level of cleaning additives)more miles between plug
changes. There are a number of US car makers advertising 100,000 miles
between plug changes in part because only unleaded gas with certain
minimum additive levels is available.
> 
> BTW the Leaded fuel here is usually has an Octane level of 92 whilst the
> unleaded fuel has octane
> levels of 97 - 98.

How do they measure octane levels where you live ? European method which
is Research method or North American which is (Research method plus
Motor method)/2. There is no empirical way to relate European and NA
methods but in general R is 8-10 points higher than (R+M)/2. In your
case no matter which method is used it doesn't seem right. Usually a
leaded fuel has the higher octane rating because TEL and MEL are the
cheapest way to raise octane in a given blend of gasoline. In any case
use the octane rating recomended in the owners manual if you have no
performance enhancing engine mods. Any higher is a waste of money.
> 
> TIA.
> 
> Regards,
> Eugene
> E34 525i M20
> Fuel delima..

Bill Matthews
Hockessin DE
Still trying to make up my mind on which BMW I want

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