Hauntednsk

Guys,

I started noticing a slight piston slap which goes away when the engine is warmed up. Piston slap only when the engine is cold and its negative temperature outside (was -10C today).
Engine oil is Mobil Truck&SUV 5w30: https://www.mobil.com/en/lubricants/...and-suv-5w-30/

Should I switch to a thinner 5w30 or thicker?

Thanks.

Gambit

iTrader: (6)

Different oil wont resolve piston slap, it's a mechanical noise...colder weather allows pistons/bores to contract at different rates hence louder when cold, and goes away when warm.

Just accept it's part of your engine warm up cycle and just go easy on it until up to operating temp

Linksfahrer

As the previous post states there is very little you can do about piston slap , it is a feature of our engines using light short skirt pistons and
this is especially true of the forged piston engines which may / probably will in comparison to some original piston assemblies
have thinner rings with larger clearance ring gaps specified.

In a forged piston /rod built semi closed deck block combined to a larger capacity oil pump / cooler , I use a good fully synthetic 10W-60
So I don''t get the benefit of the cold start lubrication capabilities that your 5W30 offers , but I can still go out in car , it just means for me leaving
it to warm up for ten minutes. I don't often see under 0 Deg C where I live but if I did need to use the car on a daily basis with your temperatures
I would probably change to 10W-40 and still warm it up for ten minutes.

You don't really want the engine running over rich in this warm up period as any un-burnt fuel sloshing around in the bore as this will break the oil film coating and cause early bore wear.
so to guard against that issue you can have your idle routine checked /adjusted in the ECU program, 1200-1400 rpm is a useful speed for the warm up phase.
And then of course (obvious) don't go out until the engine is warmed through.

stockcar

sitting a car to 'warm-up' in very basic terms is a waste of fuel.........your better driving it reasonably and letting it warm naturally as you drive

Hauntednsk

@stockcar @Linksfahrer @Gambit Gents, thank you for the replies.

My EJ205 is stock. Do those older EJs have piston shirt skirts? I thought those are not long as newer Subaru engines have.

I am in Winnipeg, Canada. We have winds and snow here, so most of the time I clean the car from snow and ice while it's warming up.
We have low temps here in Winter down to -40C with the wind. It was +6 two days ago but we gonna see -20C very soon.
Every car here has a block heater connected to the power supply in the parking lot, and mine as well. When it's -10C or lower, I plug it in overnight.
That gives an easy start and allows faster warming up. So I would not go for 10w** oil for the winter here.

Linksfahrer

At -20 my hand would freeze to the Aluminum gear ****, so I wouldn’t be driving anywhere LOL
And yes at such low temperatures 5W-30 makes perfect sense.

I wonder how many Canadians have to worry about the fuel prices , or would rather just get into a warm car before driving off .
I spent some time working in Franklin Mass, mostly during the winters. In the freezing conditions you talk about you keep yourself inside until the plough has been through, and hope the company declares it a snow day. ( Canadians burst out laughing at this point). Actually I still have family in queen’s street Toronto , they keep the car underground, but now my uncle is retired he drives every year to Florida in November for the winter. As lad in UK , I remember my neighbour Bruce ( he had a Ford Anglia that he bought when he retired from Fords Dagenham ) Bruce had experienced Winnipegs worst winters during the 1930‘s , when he worked on the Locomotives (Big Boys) his job was as engineer for startup lubricant/fire up he did a very hard job in -40 deg . To get to work he and his friend had to first light a meths burner under the sump to be able to get the oil moving enough, to hand crank.
Here we are discussing oil viscosity, he would have just smiled.

Hauntednsk

In Manitoba Province (at least) every car sold by a dealership has to have a block heater pre-installed, as winter temps are really low here.
There is no such rule in Ontario, I bought a couple of cars from there, and none had a block heater pre-installed.

However, not many people plug their block heaters most time in Winter, maybe they do plug but when it's like -30 or something.
Also looked for some neighbors around, who started their cars sitting outside, they just start the engines, wait for 15 sec and start driving, I never saw anyone who would be warming up his car. I am might be the only one in my neighborhood who plugs the block heater every night with the outside temp below -10c and warming up the engine)

Linksfahrer

For most modern cars I would broadly agree with this statement.

However some older petrol turbo cars had specific issues with this , and much depends on how the fueling / boost is managed by the ECU ,
and what you mean by "warm up naturally" as you drive.

An example Audi quattro's where in standard form 1980's designs, running boost during warmup is a definite no no , ( see urquattro.de website)
if you don't take care here you blow fuel rich mixtures into the bores and you seriously diminish its engine /turbo life.
Its actually very difficult to run off boost on this engine, even at 2000 rpm.

Having owned both diesel and petrol variants of the 10 and 20 valve since 1990 , The 6000 mile oil synthetic changes on the petrol turbo are essential,
Then when doing higher mileages you start to see higher oil consumption and you can remove the heads for new seating/guides/seals, At sub 100,000 miles bore wear is already noticeable on the 1984 Quattro
Quattro oil consumption of 1-2 liter between service I considered as normal even after doing a 100k valve guide service.

In comparison the original hone is still visible on the same 5 cylinder but Typ44 120bhp diesel turbo after 340,000 and on the Typ44 petrol Bosch injection after 220,000 miles.
the heads of these were off to resolve differences in compression by cylinder.
Then experienced oil consumption of <500ml between 20k miles oil servicing following a valve guide service replacement. ( However these were running just over half the Quattro's power )

It follows therefore that the Turbo performance car is more prone to bore wear as heavy application of throttle can cause a breakdown of the oil film lubrication.
This is particularly relevant before the engine is warmed through. I do accept that modern engine management systems can now better take care of mixture and prevent premature wear to a reasonable extent
provided you don't drag start out of the driveway and immediately roar off down the road.

Putting this in context: my point is after having spent several thousands on a EJ207 Mahle piston engine / larger turbo and its mapping, I'm less concerned to use a liter of 99Oct fuel before I set off.
I'm not about to treat my Subaru like a modern utility, I do also run a 2.0 Tdi Ford Kuga for that. Therefore I also avoid using boost in the Subaru until the engine has 50deg oil temp,
and change my oil after three thousand miles, I consider this essential for the higher tuned engines on Scoobynet, But I agree that its slightly less important for our cars if in a standard state of tune.