Dude, you're driving the best sub-60G sports coupe on the planet! this
 shouldn't be on the top of your list of worries. And as often as you
need to change it, ( unless your M3 is an oil-burner of the 7th degree -
say a quart every 1000 miles ) I dont know if that would make a REAL
difference to your bottomline dollars.

From what I've read in the past, the synthetic oils retain their
lubricational properties a bit longer than the plain old pennzoil. And I
would put my money on it, because when I switched my truck to mobil 1 my
gas mileage went up and stayed there by what I estimate to be 5-7% -
with today's gas prices - that alone will offset the costs. Although my
99 chevy is no match for your ultimate driving machine - which I think
is further reason - I would put synthetic on every car I own in a heartbeat.

With the engine problems that the E46M3 has had in the past, why risk it
by giving it another reason?

most of us here, I am not made of money and the huge price difference
between the two services is a factor for me. Of course, I will use the synth
if I really need to but my instinct says I don't. Your thoughts? TIA

AFAIK Castrol TWS is still the only oil approved for use in M3s. It still
says "Exclusively approved for use in BMW M3, M5 and Z8" on the back of the
bottle.

A $50K+ car and you want to pinch pennies on oil?  Do you drive uninsured?
Are you so tight you plan to skip scheduled maintenance?  Expensive high
performance cars require a bit more care (and expense) than a Japanese
econobox.  That should have been part of your cost of ownership equation.

As to the value of synthetic, it has greater lubricity, shear strength and
resistance to extreme heat.  Not a big deal in a beater, but it might keep
things together at 8000 RPM.

R / John

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You're driving a 50K+ car and you want to use cheap oil ? Why ?
Just use synthetic and change it every 7500 miles. I would not risky
it on such a high performance engine.
Also make sure the bearings have been replaced if it is an 01 or 02
model.