Synthetic oil change intervals

[C M Smith <cmsmith@domain.elided>]

My reply to Karl:

Don't change the synthetic oil that frequently! I have a running battle 
with my conservative Italian mechanic who wants to change the synthetic 
every 5,000 km ! The manual says 10,000 miles or every year (that's 16,000 
km) which I have done since new, except for once when my mechanic just did 
it without asking me, he no longer does that just grits his teeth and 
shakes his head sadly. The engine uses the same amount of oil now as when 
it was brand new, that is to say, a lot! Synthetic oil does not need to be 
changed more than once per year or 10,000 miles. If you get really worried 
it is the filter that might need changing more often, but I don't believe 
that. Remember also that the average Alfa engine gets two or three quarts 
of fresh oil at least in 10,000 miles!

Changing oil types on a modern car is not a problem BTW, both the seal 
materials and the oils have changed so that is no longer an issue.

My reply to Paul:

The filings were surely the result of the piston rings seating in the honed 
cylinder walls. My understanding is that the honing of the cylinder walls 
is to create a very fine metal file which files off the iron filings to 
seat perfectly in the bores. That's why you change the oil at 1000 miles on 
a  new or rebuilt engine. Synthetic oil isn't particularly useful for the 
"break in" period so conventional oil is often used. My understanding 
further is that you should not change break in oil any more often than the 
manufacturer recommends as the honing period is very important for long 
ring life.

Apparently, the science of synthetic oil is correct and verifiable. 
Synthetic does not break down nor contaminate as easily as conventional 
oil. Therefore, changing it any more frequently than specified is just a 
waste of money.

I've changed the oil and filter once per year or 16,000 km (10,000 miles) 
with no ill effects whatsoever. My 91 L has cost me a lot of money in 
repairs but the one part that is durable as hell is the engine!

Cheers


Michael Smith
White 1991 164L
Original owner
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