SomeDude

OK, had to get an urgent oil change because of a track day tomorrow.

Phone my local dealer (not the one I normally use) to ask if he could fit me in at 10 am, and I'm booked in at 2 PM

I've been there a few times, nice guy, not in to tuning much, but very helpful and interested.

I tell him about the "safe oil change procedure" much talked abut on here, and although he's not convinced that it would change much, he obliges ("why not") and fills the oil filter, disconnects sensor, let's me crank for 25 secs etc...

He then takes out his service manual, looks at it and goes "hmmm, I would have expected the oil filter to be in the "return from engine" line, but apparently it isn't... so it does make sense to fill it up this way.

Great I think. Case closed.

He then scratches his head and asks : "OK, I can understand the story of small scratches turning into engine catastrophy later on, but... why doesn't this happen on the non-turbo engines ? BHP should have nothing to do with the fact that a bearing can pick up from a small scarring occuring whilst cranking up after an oil change ? Maybe the fault would develop more slowly, but it should happen on NA engines as well. This should not be "turbo" related ?"

In my mind, he may have a point. So I would like to ask why this failure apparently doesn't happen on non-turbo Subarus ? Not to cast doubt on the procedure, but to keep the discussion going really.

Cheers.

PS: has this procedure officially been sent to UK dealers ? (I'm not from the UK, hence my question)

SomeDude

PS: he uses Castrol TWS (RS) 10W60 on *all* his Impreza Turbo cars, since day one (1996 for him). So he's not exactly stupid or lazy.

Gidney&Knowlesy

There are plenty of non turbo'd cars out there from Subarus, Ferraris, Jags et al with bottom ends going.........

SomeDude

Can't comment on other brands, so would like to keep it Subaru related (not a dig, just trying to not tangle up things...)

Are you saying big end failures are just as common on NA Subarae ?

Look, we all know it was first called "N°3 Big End". Later on, after much speculation about turbo return lines, it appeared that N°4 was even more "prone" to this problem. I've seen a few engines with at least 2 bearings gone (or more) and no sign of det on the pistons, and have been following these discussions for 5 years now...

API David (well, ain't he popular these days ) do you get NA engines in as well, at the same rate ?

scoobyboy

i asked the same question in a recent thread, considering the turbos have a lower compression ratio and they don't boost on idle theres more reason to think that n/a cars should be blowing engines more frequently than turbo'd cars.

krazy

do you see many non-turbo cars compared with turbo versions, when at a subaru garage the majority of cars going in and out seem to be impreza turbo's.
Also hasn't there been quite a few n/a big end failures in the us, certainly read a few on nasioc?

scoobyboy

when we do see one it is normally a turbo and i can only think of 1 n/a car but that had a piston break up not a big end failure

glen4

He then takes out his service manual, looks at it and goes "hmmm, I would have expected the oil filter to be in the "return from engine" line, but apparently it isn't... so it does make sense to fill it up this way.


Surely the filter would be expected to be in the supply line to the bearings, after the pump, thus giving the cleanest oil supply possible to the bearings, not the return.

APIDavid

iTrader: (4)

Somedude, Greetings from the UK !! We don't see N/a's hardly at all here. All [ well over 450 rebuilds in 3,1/2 years ] are turbo or twin turbo 2 N/A's one with loose crank pulley and the other l forget.

My opinion is that the on boost load is greater on the upper big end shell [ con rod side ] and the cumulative wear by careless oil changes or 'wrong' oil just does for the crank over a period of time. Det too, obviously.

It is a concern to us here at APi that there isn't a satisfactory explanation for ' the problem' Our experience is of a greater majority of No 3 failing. It would be nice to have an answer but I haven't found a better one than I offer here.

Good thread tho' with thought provoking points.

David APi Engines / APi Impreza