Engine oil selection

[Piper86]

Hi all,

The time for my first service is coming up ( personal first on the STI)
She's standing on 131'000km at the moment.
The previous owner was using Liqui Moly 10w60 race tech however, I'm considering going for 5w40 liqui moly. Winter is starting now and i want to assist with better lubrication on start up especially inter.

Car is a 2006 Impreza STI EJ25, it is fitted with Manley pistons, forge.

Temperatures in winter range between min -2deg Celsius and 18-22deg Celsius max. Winter is mainly may-august
Summer temperatures are usually nighttime min 20-22 and daily max 30-34 on average.
The car is currently only used for short distances driven below boost during the week by my wife and on weekends by me also mostly for short distances. We have the odd long distance trip now and then and i would love to do a track-day or gymkhana once i'm comfortable with the car and have sorted out some issues. But thats still a few months away

 

[HolyCrapItsFast]

Hello!

Is this a stock block?

Even if it was a built block, the 10W60 was a tall order and is way to extreme for any kind of street driven car. At least you had the good sense to use 5W40 which is perfectly fine for summer months. For the winter I strongly recommend you stay with the OEM recommended 5W30 unless it is a built block, in which case, the 5W40 is fine.

For any kind of track day events, I recommend changing your oil to 10W40 before the event.

As for brand, look into some AmsOil. There s no better oil on the market IMO. The Signature Series would be ideal for you.

 

[Piper86]

Yes it is a built block, forge manley pistons inside. I'm from South Africa, gave never seen AmsOil around here so got to go with whats available. Liqui Moly is the brand stocked by SubaruSA and they also recommend the 5w40. As long as ill be getting good protection at times of hard driving. However it gets driven cautiously more often and good lubrication is just as important then.

 

[HolyCrapItsFast]

I would say you are good to go then with 5w40... Do you have Motul or redline available?

 

[Piper86]

Motul for motorbikes yes, for cars i will have to search.
I can easily get Castrol Edge, Shell Helix, Liqui Molly at most places and then lesser quality items.

 

[HolyCrapItsFast]

Shell Helix Ultra or just stick with the LiquiMoly :tup:

 

[Grinder34]

the 10W60 was a tall order and is way to extreme for any kind of street driven car

Dunno if you meant just the EJ25, but 10W60 is OEM-spec on my M5. And of the 10W60 available on the market, Liqui Moly is one of only two that are generally used/recommended.

I don't know much about their 5W40 offering, but it's probably just as high quality.

 

[Piper86]

 

[Alin]

I've never ran Liqui Moly on my car, but we run it on our A8 and Passat. I don't see it being a problem for you since I run 5W-40 Rotella T6 in my car.

 

[HolyCrapItsFast]

Most modern cars :tup:... BMW is an enigma and if you ask any engineer they might tell you it is to thick for normal conditions and/or the bearing tolerances being used.. BMW spec'd that weight because the oil gets very hot under extreme conditions where the M5 is likely to be driven, if i'm not mistaken. IMO this is a flaw in design because most manufacturers do a good job of managing heat and oil temperature under any condition therefore they don't have to prescribe such an extreme oil. Though it is not perfect, the EJ does a pretty good job of regulating oil temperatures and Subaru spec'd their oil viscosity according to the bearing tolerances and emissions requirements. I looked at some threads online regarding the M5 and some people suggest using 5w30 when driving under normal conditions instead of the prescribed 10w60.

Dunno if you meant just the EJ25, but 10W60 is OEM-spec on my M5. And of the 10W60 available on the market, Liqui Moly is one of only two that are generally used/recommended.

I don't know much about their 5W40 offering, but it's probably just as high quality.

 

[Grinder34]

Most modern cars :tup:... BMW is an enigma and if you ask any engineer they might tell you it is to thick for normal conditions and/or the bearing tolerances being used.. BMW spec'd that weight because the oil gets very hot under extreme conditions where the M5 is likely to be driven, if i'm not mistaken. IMO this is a flaw in design because most manufacturers do a good job of managing heat and oil temperature under any condition therefore they don't have to prescribe such an extreme oil. Though it is not perfect, the EJ does a pretty good job of regulating oil temperatures and Subaru spec'd their oil viscosity according to the bearing tolerances and emissions requirements. I looked at some threads online regarding the M5 and some people suggest using 5w30 when driving under normal conditions instead of the prescribed 10w60.

Since this thead seems to have been resolved, I don't feel bad hijacking!

:hijacked:

The M5 forums are plagued with oil threads, and it's probably the most hotly debated topic on the whole forum. At this point, new anecdotal discussions on oil are pretty much prohibited.

BMW originally spec'd the 10W60, and then changed their spec to 5W30 coincidentally to their BMW-Approved 10W60 manufacturer ceasing production (Castrol...they still have one, but not the BMW-approved ver). Many people say it was true coincidence, and others say that there is some causation (conspiracy!). I just run the 10W60, because it seems to work, I got a couple of jugs with the car, and it's what my dad's bmw-indy told him to use.

It's interesting to know that 10W60 is so uncommon. It's also strange that the difference between 5W30 and 10W60 can be so miniscule in the S62 engine that it seems to run both just fine. It seems like there really should be an undisputed "I like this better" (from the motor's perspective) like whole vs skim milk.

 

[HolyCrapItsFast]

What is this magic that BMW is using :lol:

 

[ruan]

Hi Piper86

How is the 5W-40 working for you? I recently bought a 2006 Impreza STI with forged internals and it needs to go for a service soon. The previous owner told me to use 10w-60. I also live in SA

 

[Piper86]

Ruan,
What do you do with the car, daily drive or events on weekends?
I quite like the 5w40, i find that the piston slap is a bit less and that it smoothes out a bit quicker, the idling settles quicker in the morning.
Fuel consumption has not improved a lot but i have a few other snags to resolve first.

 

[Piper86]

Where in SA are you from?
If you do more events than daily drive go thicker but your worm up period will be longer. On daily drive like i do, change to 5w40

 

[Real Auto Dynamics]

Hi Piper86

How is the 5W-40 working for you? I recently bought a 2006 Impreza STI with forged internals and it needs to go for a service soon. The previous owner told me to use 10w-60. I also live in SA

It would help if you knew the internal specs on bearing clearances and piston to wall tolerance and ring gap. This way we can recommend the precise oil for your needs. As mentioned, driving style and environment have allot to do with the selection of your oil also. Most EJ engine builders recommend 10W40 in the summer months and in the winter months 5W40. 10W60 seems extreme to me unless it is built as a track only engine with extra oil clearances. Thicker oils like that can actually cause you to spin bearings in some cases.

How does the engine sound when the oil is at temperature? Is there allot of noise?

 

[sti_newbie]

It would help if you knew the internal specs on bearing clearances and piston to wall tolerance and ring gap. This way we can recommend the precise oil for your needs.

Would be interesting to hear more details on this if you care to explain

 

[Real Auto Dynamics]

Sure thing!

Simply put the tighter the tolerances are, the thinner the oil should be spec'd and subsequently as tolerances are widened, like in a built motor, the oil spec will get thicker. For instance in a stock motor that has very tight tolerances (like in an EJ) The engineers have spec'd an ideal multi grade oil for most normal operating conditions to be 5W30. But that is not to say that is the best oil to use if you are running the car on a track all day. In that case I would bump it up to 10W40 to allow for the extra heat generated and to provide better compressability under those conditions. However if you go too thick then the oil doesn't flow through the bearing enough to remove heat. So you could end up damaging the bearing and the journal under extreme conditions. Too thin and the oil becomes water at high temps and loses its compressability and you end up with metal to metal contact under extreme conditions.

This is true for a built motor as well but that depends on the tolerances the motor was built to. Your engine builder is generally the one to spec the oil for the build But, if you don't have those recommendations then we can make recommendations based on known tolerances if they are known. Built motors complicate things because driving habits play more of a roll in oil selection than a stock motor. That is one reason many people often use an oil cooler, to stabilize the temperature range of the oil so a normalized oil specification can be use. You can then spec a 5W40 oil year round and under any driving condition with out ever specifying 10W50 or 10W60 oil.

My first recommendation is to always consult the engine builder first and ignore any other claims unless they are from a well seasoned mechanical engineer or known good literature.

Would be interesting to hear more details on this if you care to explain

 

[Piper86]

Sure thing!

Simply put the tighter the tolerances are, the thinner the oil should be spec'd and subsequently as tolerances are widened, like in a built motor, the oil spec will get thicker. For instance in a stock motor that has very tight tolerances (like in an EJ) The engineers have spec'd an ideal multi grade oil for most normal operating conditions to be 5W30. But that is not to say that is the best oil to use if you are running the car on a track all day. In that case I would bump it up to 10W40 to allow for the extra heat generated and to provide better compressability under those conditions. However if you go too thick then the oil doesn't flow through the bearing enough to remove heat. So you could end up damaging the bearing and the journal under extreme conditions. Too thin and the oil becomes water at high temps and loses its compressability and you end up with metal to metal contact under extreme conditions.

This is true for a built motor as well but that depends on the tolerances the motor was built to. Your engine builder is generally the one to spec the oil for the build But, if you don't have those recommendations then we can make recommendations based on known tolerances if they are known. Built motors complicate things because driving habits play more of a roll in oil selection than a stock motor. That is one reason many people often use an oil cooler, to stabilize the temperature range of the oil so a normalized oil specification can be use. You can then spec a 5W40 oil year round and under any driving condition with out ever specifying 10W50 or 10W60 oil.

My first recommendation is to always consult the engine builder first and ignore any other claims unless they are from a well seasoned mechanical engineer or known good literature.

Very interesting read, thanks for the info.
The above is what i dis when selecting my oil however I had some dead ends so i decided to change the grade die to my application. My piston slap has reduced.

I see you mentioned multigrade, I'm running Fully Synthetic. Any comment or pro's and con's on this?

 

[ruan]

I'm live about 50km from Cape Town and you? I use the car daily with the occasional sprint (would like to do a trackday in the future). I don't know what the internal specs. Still trying to find out the history of the car. The piston slap seems to almost go away when the oil is on temp, but i'm new to all of this... i'm used to 8v opel noises :lol:

A technician from Subaru advised to stick with 10w-60