I see it mentioned so many times, I can't help but respond as the facts often quoted on these boards are completely wrong!

Why is it that in some Subaru manuals warn against the use of 5w-30?

This is because the use of sae 30 is not recommended and in fact has nothing to do with the "w" number which is 5.

This leads to comments like:

"You must not use 5w oils"

"5w oils are too thin"

"Use 10w-40 but not 5w-40"

Some facts need to be straightened out here and hopefully I can do this without losing those that are interested. Others will undoubtably pick parts of the post, quote them and then pick a fight with me turning this into a ridiculously confusing thread - Let's hope not.

So, given that sae 30 is not recommended what are the reasons?

SAE 30 must be in Subaru's opinion too thin at higher temperatures (100degC) for the engine to give the adequate metal to metal contact protection that the engine requires over a period of time as all oils shear (lose viscosity) with use.

I do not often recommended to use of sae 30 oils for any scoobies new or old although it does appear that some of the newer models do not exclude the use of 5w-30 or 10w-30 and some technical databases list these grades.

I usually tend to recommend the use of sae 40 and sae 50 as the best options depending on the age and specification of the car.

So what is the difference between a 5w-40 and a 10w-40 @100degC?

Basically NONE!

SAE determines the viscosity (+/-) that the oil needs to be at 100 degC and these need to be met in tests to give the oil it's API rating (xw-xx or xxw-xx).

They are as follows: (within a margin)

SAE 30 = 11.00cst
SAE 40 = 14.00cst
SAE 50 = 18.50cst
SAE 60 = 24.00cst

Compare these SAE 40 oils at 100degC (0w, 5w, 10w, 15w)

Motul 300V 5w-40.................Viscosity = 13.80cst
Motul 300V 10w-40................Viscosity = 14.00cst
Silkolene PRO S 5w-40............Viscosity = 14.89cst
Motul 8100 X-cess 5w-40........Viscosity = 14.00cst
Fuchs Titan Supersyn 5w-40....Viscosity = 13.60cst
Castrol Performance 10w-40.....Viscosity = 14.50cst
Silkolene XTR 10w-40 (semi).....Viscosity = 14.70cst
Mobil 1 0w-40........................Viscosity = 14.30cst
Motul 8100 0w-40...................Viscosity = 13.30cst
Silkolene Turbolene D 15w-40....Viscosity = 14.40cst
Total Quartz 15w-40...............Viscosity = 14.50cst

These figures are not by chance and include synthetics, semi-synthetics and mineral oils they are all in the range to be labelled a Xw or XXw-40 multigrade oil.

So, what's the "W" number all about then?

It stands for "winter" not "weight" as often confused and called on many U.S. articles on oil!

This number is the "cold crank" viscosity and nothing to do with the oil viscosity when the engine is up to temperture. These numbers are related to the oils ability to operate in cold temperatures. 0w oils were originally designed to operate in arctic climates that's why they operate at ferrous monkey endangering temperatures of -35degC and below!

The benefits of the lower viscosity oils (0w and 5w) is that they flow more easily and quickly when cold and therefore protect the engine better on cold start when 80% of the engine wear occurs.

So, yes it's true an sae 40 is an sae 40 when hot whether its a 0w, 5w, 10w, 15w or whatever and that's a fact. The same goes for 20's, 30's, 50's, 60's and so on.

Hope this helps.

Cheers
Simon

 

So using Mobil 0W40 as an example, why do you think people have warned owners away from this grade of oil?

This particular example of manufacturer and its recommendations for the Subaru isn't a recent thing, but has been around since the last millenium from at least late '98, early '99. (this is when i started Subaru ownership and had no problems in the use of that particular oil in another application beforehand)

Why do you think that is?

{genuine question, not a flame}

 

The benefits of being an authorised advertiser!!

 

0w is TBH "overkill" for our climate and 5w or 10w are more suitable. However I don't see many scoobs in the book where 0w is listed. 5w seems to be a more common recommendation. I personally have no problem with 0w but as with my comments on past threads concerning SAE 60 oils, I'm not going to recommend them to you if I can't find the oil listed in the databases.

Cheers
Simon

 

pimpdaddy

 

oilman - good idea with the thread...

just a question, people (myself including) may still wonder which is best for their car. So would you be able to advise by putting up a rough list - i.e early classics should use...... etc or by mileage upto 30K then use this or 50K use that..? just woundering as i reckon it would be a great help for everyone.

thanks mate.

 

I take it what you are trying to make clear in this thread is that any synthetic oil is suitable providing it falls within the rating guidelines of (5-15)W(40-60) ?

i.e. 5W40
10W40
10W50
15W50
10W60

etc?

I haven't read the other threads but what's the big deal here? Surely all you are trying to get across is that we should all be using oil gradings as recommended by Subaru? or am i missing something?

My only mention of the Mobil example was purely down to past experience on another marque which was turbocharged. At the time without thinking, i would have carried on using what i was happy with 'til i was told otherwise when i found this site all those years ago.

 

Rather than turn this into another recommendations thread, here are the recommendations from several professional sources.

http://bbs.scoobynet.co.uk/showthrea...ghlight=oilman

Feel free to ask any recommendations questions there or simply PM/Email me if you wish.

Cheers
Simon

 

Depending on the car, year and mods anything from 0w to 15w and sae 30 to 50. The recommendations I made some time ago are here so take a look. Also at your handbook and if modified just ask.

http://bbs.scoobynet.co.uk/showthrea...ghlight=oilman

Cheers
Simon

 

cheers oilman

 

Thankyou simon ...Something I've always noticed about oil recomendations given on this site seems to give advice relying more on the cold temp ratings more so than the hot.

Many a times have I seen it mentioned, and just couldn't bothered to get drawn into a long winded debate of how the viscosity rating system works.

My thought has always been this - google is your friend there is plenty of factual sites that'll teach you everything you need to know about oil and how the ratings systems work. Then you can compare and understand publically available MSDS of each oil. From that you can make up your mind which oil is better without asking anonymous "experts" Suffice to say - what I have read up on has all backed up what Simon the oilman says

 

Indeed, I think my sig says it all. We all do something for a living afterall!

Cheers
Simon

 

Just curious. I'm running just a decatted 02 WRX and now have Motul 300V 15-50. Is that a bit too thick? As it may be a bit thicker should I let the engine run for a few mins before driving gently? I make sure that I stay off boost for a good 10 mins.

Also, is it worth changing the oil as the seasons change, eg, 15-50 in Spring to Autumn but something thinner for Winter?

Cheers!



Mike

 

Hi,

looking at the oil working tempretures info from oilmans link above:

-20°C and above, 10W-40 or 10w-50
-15°C and above, 15W-40 or 15w-50
-25°C and above, 5w-30 or 5w-40

I know boll*x all about oil but realy can not see a reason for using oils that initaly protect past -15°C cold crank while I am living in the mainland of UK.

Am I missing something here? Why take any risk (if there is any) and use 5wXX oils?

Personaly I will stick with my 15w50 oil and just make sure I dont drive the car if it ever goes past -15 outside

 

Mike,

The answer is a little complicated and somewhat down to personal choice however the technical factors that you need to take on board are.

The recommended grade for your car is 5w-40. Can you use 15w-50, yes why not but it wouldn't be my recommendation.

Unless you are getting high oil consumption or low oil pressure there are no benefits to using a 15w-50 because...........Thinner is in fact better.

Thinner oils dissapate heat better.

There is less oil drag and therefore in most cases this translates to marginally higher BHP at the wheels.

Thicker oils are more likely to cause cavitation.

Thicker oils are slower to release air.

Thinner oils give better fuel consumption returns.

So you see it's not a case of "can I use it" but more a case of are there any benefits and I cannot see any in the case of a pretty standard spec car other then the old and incorrect addage of "thicker is better".

If you are worried about an sae 40 being too thin then look at the oil temperatures you are running and remember that a 5w-40 is in fact thicker at 110degC (12.06cst) than a 15w-50 is at 140degC (8.25cst).

Finally, yes on 15w-50 let the car warm properly before "blatting" it is good advice although the ester in 300V will ensure that there is always a thin film of oil in the engine at start-up as it's surface-active.

Hope this helps

Cheers
Simon

 

could be a potentially intresting thread if all the big guns get involved

 

I need to clear up a common misconception about my business too.


it is prounced Pat ent as in the name Pat, not as in Patent leather.

I feel as an expert and a professional it is my duty to tell you all, and educate those who haven't spent any money with me yet.

 

After reading many posts about oil, I believe that if a good quality full synthetic is used then its not that important which oil it is.

If as Simon says that 80% of engine wear occurs in the first few minutes of starting the engine, I would prefer an oil to flow to all parts as quickly as possible.

I think alot of damage/blow ups are due to cars being driven hard upto the redline repeatedly. I personally, very rarely go above 5500rpm and if I do its when the car is warmed up.

There is a recent post of a fella who looks like he has blown his engine after a oil change, then driving the car at speeds of 140mph after only three miles. It could be that he didnt fill the oil filter prior to fitting and/or it could be that he thrashed the pants of the car far too early.

My opinion would be to use good quality oil( whatever grade / manufacturer), warm the car up, dont go over 5.5k-6k rpm often and let it cool down properly.

Andy

NB
Ive always used mobil1 0w-40 on my uk97 turbo, 80k miles,(no loss of oil between oil changes), owned from new.

 

[QUOTE=andy97]After reading many posts about oil, I believe that if a good quality full synthetic is used then its not that important which oil it is.

If as Simon says that 80% of engine wear occurs in the first few minutes of starting the engine, I would prefer an oil to flow to all parts as quickly as possible.

I think alot of damage/blow ups are due to cars being driven hard upto the redline repeatedly. I personally, very rarely go above 5500rpm and if I do its when the car is warmed up.

There is a recent post of a fella who looks like he has blown his engine after a oil change, then driving the car at speeds of 140mph after only three miles. It could be that he didnt fill the oil filter prior to fitting and/or it could be that he thrashed the pants of the car far too early.




Exactly what I think Shell Helix Ultra £21 5 litres. Its a car made for driving....

 

Thanks Simon for your help. I'll probably keep the 15-50 in for another thousand miles and go for a slightly thinner oil.



Mike

 

Thats interesting, so when you start-up in the morning after the engine standing for 8 hours - there is a film of oil protecting the moving parts/surfaces?

In the same way, that would protect the engine on an oil change with the oil draining into the sump over a time period of about 30minutes ... the oil would protect surfaces during start-up after an oil change?

Pete

 

It's ester that's the key component here. Usually it's blended with pao (poly alpha olefin) and in the best oils there is often 20% ester / 80% pao.

Pao's are inert and esters are polar.

Esters

All jet engines are lubricated with synthetic esters, and have been for 50 years, but these expensive fluids only started to appear in petrol engine oils about 20 years ago. Thanks to their aviation origins, the types suitable for lubricants work well from –50 degC to 200 degC, and they have a useful extra trick.

Due to their structure, ester molecules are “polar”; they stick to metal surfaces using electrostatic forces. This means that a protective layer is there at all times, even during that crucial start-up period. This helps to protect cams, gears, piston rings and valve train components, where lubrication is “boundary” rather than “hydrodynamic”, i.e. a very thin non-pressure fed film has to hold the surface apart. Even crank bearings benefit at starts, stops or when extreme shock loads upset the “hydrodynamic” film.

Hope this explains.

Cheers
Simon

 

Simon whilst I have "had a bit of a go" from time to time my reasons are simply that you have appeared in the past to take no account of a car that has been modified away from standard, these cars, of course, have completely different needs to those that are std.

So, and this is genuine not a wind up or anything like that, I will describe my own car's engine situation, also the oil I use (have used).

First engine spec (generally not specifically as I have some p&c bits)

Pistons are Omega forged with clearances designed to run 2 bar boost to 8500 rpm
Rods are Arrow uprated
Crank is STi WRC nitrided with extra drillings.
Mains and big ends are now new age latest type.
Fly wheel is 6kg
Pulley set is aluminium and crank damper is dispensed with.
Engine rev limit is 8200 rpm
Boost is normally 1.85 bar to the red line.
EGT's don't exceed 865 deg C measured in the collector.
Fuel is Optimax and 1.5mls NF per litre.
gearbox is six speed
Clutch is STi uprated at 1.2 tonnes clamping force.
AFR's are confidential but are typical, egt info is more important, there is negligable oil dilution from cylinder cooling using fuel.
I use a catch can and no breather feeds back into any part of the intake
PCV is blanked.

I use either Castrol RS 10-60 or Motul M300V 15-50, of the two I prefer the Castrol as pressures are similar at idle throughout its service life (changed oil and filter every 3500 miles) and more importantly oil temps are 6-8 degrees lower. The Motul seems to have a better viscocity index.

So based on the above, which is probably an extreme mod state but one that many are working towards, what would your comments be. I don't pretend to be an expert in oil technology however I do, like many, rad all the techy bulitens and fact sheets provided by the oil manufacturers and being "trade" as it were I do get much more info than "joe average".

As I said this isn't designed to catch you out, modified cars do need different thought processes, if you don't feel able to respond then fine no problem from me, but if you can apply some input then golden opportunity.

Personally I aklso use Shell Helix Ultra 10-40 for running in and this oil in its own right stands up to serious mapping abuse, what are your thoughts on the SHELL 10-60 race oil thats now on the market ? The 10 bits right and at egt's in the mid/high 800's then the 60 seems logical.

bob

 

A yes or no would have been sufficient

I assume that start-up after an Oil Change is fine as the surfaces are protected during those vital moments that the pressure takes to rise?

Pete

 

the oil on the surfaces has to last longer as there is no oil in the filter or above the filter etc.. as many people will tell you there is a connection between oil changes and big end bearing failures on the Subaru engine.

As to this thread perhaps a link to one of Oilmans first posts??

http://bbs.scoobynet.co.uk/showthrea...ghlight=oilman

says it all really I think if you read the replies from the respected people on here..

Some people are too quick to trust peoples opinion and start treating them like some god.. when the reasons for their posts are clearly down to them trying to earn money from it.

 

Indeed, I posted it a long time ago and it was originally commissioned (the article that is) by SIDC. It was written by John Rowland who is the Chief R&D Chemist for Silkolene. John is not a salesman and extremely respected in the Oil Industry for his opinions and technical articles. I know him well and have sought his advice on many occasions. I also have his personal permission to publish part or all of his articles whenever I like.

The important thing is that he knows what he's talking about and you could do worse than to read his article "lubricating the Subaru" thoroughly!

The fact that I sell oils is relevent but it does not detract from the quality of the technical advice that I give. It's free and you don't have to read it.

More importantly, I don't sell 1 brand I sell 6! This enables me to see a broad range of products (around 250 engine oils) and compare/analyse the qualities and benefits of them. This experience can only be achieved by access to a wide product base.

Sorry you are cynical but I always try to be objective and helpful in my advice with the many clubs that I work with.

Cheers
Simon

 

Bob,

There are no hard feelings this end and "having a go" is not a criminal offence in my book. Everyone is entitled to their opinion - That's the strength of a healthy forum.

Yes I am more than happy to take a look at the most suitable oil for your car but please bear in mind that my mechanical knowledge is way inferior to yours as it's not my specialist field.

So, can you please answer a couple of basic questions as I am going to talk to some technical people today and get back to you with my thoughts.

1. You mention 1.5 mls of NF per litre, is this an octane booster and what is it?

2. What (assuming you monitor it) are the oil temperatures you see in different conditions idle/road/track?

3. Assuming that you use the car for competition, what type, how often and the general time periods involved in a session?

4. What is the BHP above stock?

5. What engine and year is it?

Thanks in advance.

Cheers
Simon

 

Simon the Oilman,

Thank you very much for the info supplied regarding oil viscosity and performance and so -on, I am now better informed, not wiser, just better informed.

I have been under the misconception regarding the ?w number and understand better what it actually means.

However, I still think it not advisable to put 0W and 5W in a Subaru in the UK it does appear to cause problems.

I will continue to advise 10W or 15W just be on the safe side where Subaru is concerned. Particularly in light of APi's experiences with import cars.

And; I still stand by the rule, NEVER put flushing oil in a Subaru.

Thanks again for an interesting insight to your 'sticky' world.

David APi Engines / APi Impreza
www.apiengines.com

 

David,

Thanks for your kind comments.

Just one question for you as your technical experience with scoobs is far better than mine.

Whilst I understand your stance particularly with pre 2000 models, how do you reconcile this with later models where 5w-30 or 5w-40 are recommended?

Just curious David, I'm certainly not questioning your knowledge.

Cheers
Simon

 

APIDavid's Indian name "Wise Owl".....I was going to put the words old, though thought that far too unkind