swampy2008

hey ppl, I'm now a Scooby owner after saying for years its just a family car , it turns out its 2000 gc8 wrx sti. what engine oil would be best, its done 120k, no mods, but its got some go in it , cheers steve

oilman

iTrader: (9)

Hi Steve

I would use a 5w-40 synthetic and you will find those through the link below.

http://www.opieoils.co.uk/c-656-5w-40.aspx

Out of those, the best ones are the Fuchs/Silkolene Pro S, Millers CFS/CFS NT+, Motul Sport/300V, Red Line, Amsoil and Gulf Competition. The Motul 8100 X-Cess, Millers XF Longlife, Castrol Edge/Magnatec, Fuchs GT1 XTL/Supersyn, Shell Helix and Mobil Super 3000 are good, cheaper alternatives.

Cheers

Tim

AS Performance

iTrader: (4)

personally i wouldn't use 5w in a classic in the UK and its the "wrong" recommendation..........

for general use then use a high quality 10w40 of for more aggressive use then a 10w50, etc....

we carry various on the shelf and always deals available 0191-4103770

oilman

iTrader: (9)

That is just your "opinion". Subaru are still recommending 5w-30.

ZANY

I use millers cfs 10/50 previously the 10/40 in both mine and my brothers scoob

5/30 more for a newer car to protect the environment etc

I'd stick to a good quality 10/40 or 10/50 if more aggressive driving takes a little more time warming up but does an excellent Job from cold to hot
some of my mates are using mobile 10/60 fully synthetic and happy with it aswell

AS Performance

iTrader: (4)

of course, i didn't read it in a book (as yourself) so it must be wrong after all we wouldn't know much about these subaru engines or their potential pitfalls....................

as mentioned above the lower weight is only recommended for the newer cars and even then we substitute for a different grade if used aggressively, tracked,etc......

oilman

iTrader: (9)

I know you know about these engines as you bang on about that quite a bit. As you know we know about oil.

However, my point was it is not "wrong", that is only in your opinion. If Subaru are still recommending 5w then who is wrong and who is right? Its just opinion, as you know, we have ours! And we don't always recommend 5w, as you will know.

If I am incorrect, please can you point me to Subaru's recommendation to show me it is "wrong" officially.

swampy2008

many thanks peeps, I'm still none the wiser lol ,

oilman

iTrader: (9)

Hi

Yes, you probably will be. Unfortunately, with oil there are a lot of opinions on what is best. On most oil threads, you will see that me and AS Performance have a different opinion, but in reality there is little difference between 5w-40 and 10w-40. As you car is not modified, then there is no need for a thicker oil like a 10w-50 or 15w-50, so I would go for a 5w-40 or 10w-40.

Cheers

Tim

Bazil_SW

iTrader: (4)

I would say if it's not modified, use the recommended oils as per the service manual, but perhaps use to thicker end, such as a good 10w40. My logic would be if the car has 120k miles the bearings might have worn and thicker oil would help there where a thinner oil might not be as effective. As mentioned manufactures opt for thinner oils, 5w30 for example, because they want reduced engine friction and so improve fuel economy, and they can do so by closing up the bearing clearances.


From my understanding oil 'choice' becomes more critical when the engine has uprated/race bearings that have a larger than design intent clearance, you then would be inclined to consider 10w50 or higher.

TECHNOPUG

iTrader: (1)

The numbers indicate the viscosity (thickness of the oil) at cold (low number) and hot/optimum temp (high number).

So a 10/40 is thicker than a 5/40 at cold temp but the same at hot temps. A 10/50 would be thicker at hot also but only advised for engines that run hot due to regularly high-rev driving (track days etc)

If you run a 5/40, it's thinner at cold, which means the old creates less drag on the engine and gives better performance & economy than a thicker 10. Hence why manufacturers prescribe 5w30/40 from new.

However, as engines wear through use and age, a thinner oil offers less protection at cold, as the engine (rings, pistons etc) take longer to expand and seal. As most wear/damage is done to an engine during this cold phase, a thicker oil is advised to offer more protection.

I don't know how many 100k+, 10 year+ UK engines that Subaru strip & examine each year in order to determine the correct grade of oil for used engines - I'd suggest the number is zero.

If in doubt, use 10w40 as the worst it will do is rob a little performance and economy. Or, you could be a little more scientific and start with 5w40 and regularly record the oil level/consumption. If it doesn't use any oil, fine. If it does, then switch to 10w40 and repeat. Whichever consumes the least oil, stick with.

Gambit

iTrader: (6)

im pretty certain uk classic service manual said to use quality 10w40 SEMI synthetic minimum!

understand OP's is a STI so probably slightly different using fully synthetic but i wouldnt be putting 5w near any classic nevermind one with 120k on it (be it miles or kms)

oilman

iTrader: (9)

A 5w is only thinner than a 10w when cold, so it flows quicker from cold and gives better cold start protection. With some classics, you get piston slap and a 10w helps to cover that up, but it isn't giving better protection as the oil is taking longer to get around the engine.

And when it says 10w-40 synthetic as a minimum, a 5w-40 synthetic is an upgrade over that.

Another thing to consider is that the handbook is 17 years old (at least) so it can't take into account advances in oils since then

Cheers

Tim

AS Performance

iTrader: (4)

cant see anyone "banging on" apart from spam oil posts.................

i dont have any Subaru service data here to hand but i cant recall even Subaru suggesting a GC8 Turbo car to use a 5w apart from specific artic type climates...........so why dont you show the data you have???

just out of interest i have just checked various oil company online "oil recommend" checkers and not one suggested 5w so i still stand by the 10W40 min that i first recommended

the issue with most modern manufacturers is that there oil suggestions are blatantly related to maximising economy with no thought or heed to long term "life"

oilman

iTrader: (9)

What spam posts? I don't see any.

5w and 10w have nothing to do with economy, they only relate to cold start protection.

Online oil look ups are always based on bog standard recommendations, they do not look at improving on that (by increasing cold protection). By choosing a 5w oil over a 10w, there is no effect on the hot protection, it 's only on the cold start, so actually, a 5w-40 will offer better longevity than a 10w-40.

I'm not sure why you think we recommend oils for economy, I really pay little attention to that as the difference an oil will make is pretty minimal.

Cheers

Tim

TECHNOPUG

iTrader: (1)

I don't think that anyone is arguing that a thinner oil doesn't potentially give better cold start protection on a new engine. It's which oil is best to run on an older, high mileage engine? I'd suggest that an oil can be too thin and that then becomes a detriment to protection, rather than a positive.

oilman

iTrader: (9)

Hi

Not really. The oil is so much thicker when cold than hot that it is still advantageous to use a thinner variant when cold in a high mileage car. My car has 162k on the clock and uses a 5w oil. Thicker oil is only really a bonus when the engine is so worn that there is piston slap when cold. Even then it is debatable, as it will be giving less protection due to the lower flow rate, it just covers the noise of piston slap better.

Cheers

Tim

Gambit

iTrader: (6)

on that rationale then why not switch to 0w oil which is thinner again?

oilman

iTrader: (9)

With 0w, there is less of a range to pick from, they are generally more expensive and in the UK it doesn't get cold enough to need a 0w. Also, with older cars, there is more likely to be piston slap, a 0w can be that bit too far. I've dealt with a few guys using Mobil 1 0w-40 in classic imprezas without issues though, but there have also been a couple that have had piston slap with it.

Cheers

Tim