Good points raised here, but I'm still confused about what oil to use. As far as I can see 10W-40 (recommended for normal use) and 5W-30 (recommended for use in very cold conditions) are only available as Semi Synthetic oils.

Fully synthetic (Castrol RS, Mobil 1 etc etc etc) only gives you the choice of 0W-40 or 0W-30. I've never seen a fully synthetic (retail) that starts with anything other than 0W.

So what's better, 10W-40 Semi or 0W-40 Fully synthetic?

 

Motul Chrono 10w-40 100% double ester synthetic, they do a 5w-30 as well, bang in with what your hand book says.

Cheers

Simon.

 

I know exactly what you mean, The amount of threads I see where I see this with information posted by someone that is just partly regurgetated by someone else, with no 100% factual knowledge of what they are talking about. There is only so many threads where you can correct people and give them the correct relevent information.

I notice also many people spouting oil recomendations haven't a clue on the viscosity numbers they are quoting.

Things like the following pop up so often it's unbeliveable. For example: "0w-40 or 5w-40 is too thin...use a 10w-40 instead!" is very very irritating.

I, and a few others know that the above is missleading and to all intents is incorrect. But to the poor people asking the questions, take it onboard as sound advice. I so wish people who do not have any proper knowledge of the question at hand just not bother answering the question, and leave to someone who has a clue of what they are on about.

keep up the good advice oilman, we need a few more round here to get things straightened out

 

Well, I have never given any oil recommendations, just like asking questions, but for the info of the gentleman (s70rjw) above, I regularly run castrol RS 10w-60, have done for many years, and it has never let me down in cars that run 15K per year (usually kept for 3 years) and can be purchased at a trade supplier for a very keen price. The only stuff that has ever let me down was Mobil 1 (stupidly 0w-40), but perhaps running the engine at 7000-7500 rpm in fifth for 1- 1.5 mins was more foolish than to be blaming the oil.
I fully respect that oilman has a great deal of knowledge on these subjects, but just wish more of his posts were in layman's terms!
Craig

 

I'm not sure how more layman it can be when I say use 5w-30/40 or 10w-40/50 depending on your driving style.

It's certainly straightforward to look in your handbook and see that I'm not talking out of my rear end when I say 10w-60 is not specified.

Modern cars (BMW accepted on some models not all as stated and I stick by that. Dealers should really read the BMW circulars properly. No offence intended)

E.G. M5 up to 02/2000 10w-60 (changed from handbook recommendations) after 02/2000 use 0w-30/40, 5w-30/40 LL01. I have confirmation of this in writing from both BMW and Castrol.

I digress, scoobs.

The problem. Oil is such an emotive subject and at the risk of upsetting anyone (which is not my intention) many people follow like sheep due to fashion or advice from people that should know better as they only have to look at the handbook to see what Subaru recommend, why ignore it?

My recommendations are based on access to the information in your handbook but via a database which covers the full recommendations for every lubricant for every part of your car and every other car produced in the last 20 odd years!

I find the debates here fascinating as it takes 5 minutes to get the handbook and check what's correct and make your own judgement.

As I've said before, it's not my car or my money so it's your choice but do yourself a favour and look before you buy, don't just buy an oil because others do, afterall, others can be wrong!

Enough for now, I'm always about so just ask If you need some advice.

Cheers
Simon

 

i,ve use 5w30 full synth (and not even a well known one, but with a high spec) for 3 years now, with out a problem.

it even seem to produce a touch more power with the "thinner" oil in her, due to less drag on the crank .etc etc

 

5w-30 will give better power delivery due to less oil drag, remember the tests that the Silkolene chemists did on 15w-50, 5w-40 and 0w-20? There were marked difference in BHP and Torque with the thinner oils.

For those that missed it, here it is:

quote:

Must Have MORE Power!

Motorcars are bought for all sorts of reasons, but enthusiasts like lots of power. To get more power, a lot of fuel must be burnt, and more than half of it, sadly, gets thrown away as waste heat. For every litre of fuel burnt, 60% of the energy goes as waste heat into the exhaust and cooling system. A turbocharger can extract a few percent as useful energy and convert it into pressure on the intake side, but only 40-45% is left, and only 25% actually shows up as BHP at the flywheel. 6% goes in pumping air into the engine, 6% as oil drag losses and 2-3% as engine friction. The oil deals with 97% of the friction; so reducing the remaining few percent is not easy. If you doubt that even ordinary oil has a massive effect, take a clean, dry 200 bhp engine, connect it to a dyno and start it up. It will only make 1 bhp for a few seconds. Now that’s real friction for you!

Oddly enough, people get starry-eyed about reducing friction, especially those half-wits who peddle silly “magic additives”, which have not the smallest effect on friction but rapidly corrode bearings and wallet contents. In fact, even a virtually impossible 50% reduction in the remaining engine friction would be no big deal, perhaps one or two bhp or a couple of extra miles per gallon.

Even More Power!

He place to look for extra power is in that 6% lost as oil drag. In a well-designed modern motor, the oil doesn’t have to cover up for wide clearances, poor oil pump capacity or flexy crankshafts, so it can be quite thin. How thin? Well take a look at these dyno results.

A while ago now, we ran three Silkolene performance oils in a Honda Blackbird motorcycle. this fearsome device is fitted with a light, compact, naturally aspirated 1100cc engine which turns out 120+ bhp at the back wheel. The normal fill for this one-year-old engine was 15w-50, so the first reading was taken using a fresh sump-fill of this grade. (The dyno was set up for EEC horsepower, i.e. Pessimistic)

15w-50
Max Power 127.9 bhp @ 9750 rpm
Torque 75.8 ft-lbs @ 7300 rpm

After a flush-out and fill up with 5w-40 the readings were;

5w-40
Max Power 131.6 bhp @ 9750 rpm
Torque 77.7 ft-lbs @ 7400 rpm

Then we tried an experimental grade, 0w-20 yes, 0w-20! This wasn’t as risky as you may think, because this grade had already done a season’s racing with the Kawasaki World Superbike Team, giving them some useful extra power with no reliability problems. (But it must be said, they were only interested in 200 frantic miles before the engines went back to Japan)

0w-20
Max Power 134.4 bhp @ 9750 rpm
Torque 78.9 ft-lbs @ 7400 rpm

In other words, 3.7 bhp / 2.9% increase from 15w-50 to 5w-40, a 2.8 bhp / 2.1% increase from 5w-40 to 0w-20 or a 6.5 bhp / 5% overall. Not bad, just for changing the oil! More to the point, a keen bike owner would have paid at least £1000 to see less improvement than this using the conventional approach of exhaust/intake mods, ignition re-mapping etc.

Am I recommending that you use 0w-20 in your Subaru’s? Well, perhaps not! The 5w-40, which is a “proper” PAO/Ester shear-stable synthetic, will look after a powerful engine better than a heavier viscosity “cave at the back” conventional oil, and provide a useful extra few BHP.

Unquote:

Hope this helps to explain the theory behind friction and oil drag.

Cheers
Simon

 

Quote

Fully synthetic (Castrol RS, Mobil 1 etc etc etc) only gives you the choice of 0W-40 or 0W-30. I've never seen a fully synthetic (retail) that starts with anything other than 0W.

Message.

As I mentioned earlier on the posts on page 1

both shell helix ultra and BP visco 5000 are both fully synthetic 5w-40 oils and easily available (I think you can work out where from).

The shell Helix ultra was about £23 for 5 litres and you get a free ferrari cap, it was on a poster on the forecourt this morning.

You are correct a lot of fully synthetic oils are 0w but that is becuase the majority of mass market cars now use this oil, modern VAG, BMW ect ect. Subaru are behind the times in my opinion for not testing these oils and making changes to benefit from them.

If you go to a motor store there are probably others. But in my opinion you are better off mail ordering some specific oil. Motul, Silkolene ect as it probably will not cost you anymore. If you provide trhe oil for your service you will save money, just check with your delear the oil you are using is OK and they are willing for you to supply.

I am currently using mobil 1 5w-50 not had any issues but i bought this in France so will have to find something new for the next service, as it is not sold in the UK.

 

Modern cars (BMW accepted on some models not all as stated and I stick by that. Dealers should really read the BMW circulars properly. No offence intended)

E.G. M5 up to 02/2000 10w-60 (changed from handbook recommendations) after 02/2000 use 0w-30/40, 5w-30/40 LL01. I have confirmation of this in writing from both BMW and Castrol. (Quote)

No offence taken, and I do apologise for not taking note of dealer info before posting, but the range of M5's that you are indeed correct about, is very small and did not sell in there masses like M3's(which have had 2 massive recalls on the big end bearings) and the other M-sport vehicles which after careful checking on the latest up to date literature, all require 10w-60 oil, but thanks to this thread, I have found that Castrol list (admittedly on a BMW tech sheet), a 5w-40 Castrol RS oil, are you able to supply this oilman (I prefer to use Castrol as Brand loyalty) or would you advise using a 10w-50 oil. I need to put this into a Legacy GT-b and a 04 WRX PPP
Craig