Your Oil Questions answered

A bit of explanation on oil selection and the reasons why.

Surely the thicker the oil the better!

This isn't always true - even when using a petroleum oil. Although it is true that heavier viscosity oils (which are generally thought of as being thicker) will hold up better under heavy loads and high temperatures, this doesn't necessarily make them a better choice for all applications.

On many newer vehicles only 0w-40, 5w40 or 10w40 engine oils are recommended by the

manufacturer. If you choose to use a higher viscosity oil than what is recommended, at the very least you are likely to reduce performance of the engine. Fuel economy will likely go down and engine performance will drop.

In the winter months it is highly recommended that you not use a heavier grade oil than what is recommended by the manufacturer. In cold start conditions you could very well be causing more engine wear than when using a lighter viscosity oil. In the summer months, going to a heavier grade is less of an issue, but there are still some things to be aware of.

Moving one grade up from the recommended viscosity is not likely to cause any problems (say from a 10w40 to a 10w50 oil). The differences in pumping and flow resitance will be slight. Although, efficiency of the engine will decrease, the oil will likely still flow adequately through the engine to maintain proper protection. However, it will not likely protect any better than the lighter weight oil recommended by the manufacturer.

Moving two grades up from the recommended viscosity (say 10w40 to 10w-60) is a little more extreme and could cause long term engine damage if not short term. Although the oil will still probably flow ok through the engine, it is a heavier visocosity oil. As such it will be more difficult to pump the oil through the engine. More friction will be present than with a lighter viscosity oil. More friction will be present than with a lighter viscosity oil. More friction means more heat. In other words, by going to a thicker oil in the summer months, you may actually be causing more heat build-up within the engine. You'll still be providing adequate protection from metal to metal contact in the engine by going with a high viscosity, but the higher viscosity will raise engine temperatures.

In the short run, this is no big deal. However, over the long term, when engine components are run at higher temperatures, they WILL wear out more quickly. As such, if you intend on

keeping the vehicle for awhile, keep this in mind if you're considering using a heavier weight oil than the manufacturer recommends.

The best advice is to is to stay away from viscosity grades that are not mentioned in your owner's manual.

Cheers

Simon

Allow me to introduce myself.  I work for a specialist lubricant manufacturer, supplying industry all over Europe.  We don't manufacture 'standard' products nor indeed do we supply the general public, so I assure you I'm not after any personal gain.  Firstly I would like to say that SIMON offers a fantastic service here and after reading all of the posts here I agree with 95% of what Simon writes, I'm definetly not saying that he is 5% wrong, just on certain things everyone has their own slant, that's what makes the world interesting surely !

I agree that Esters or PAO oils are the best oils to use, no doubt.  There are certain other factors you must consider.  You can use too good an oil in your engine and actually cost yourself a lot of money, allow me to elaborate.......... Put the kettle on, slide in to your slippers and get comfy, please read on. 

You must remember that a lot of older cars will not always have been using Fully Synthetic oils.  Generally speaking Fully Synthetic oils have got the best all round packages, including detergents.  If you can be sure that your car has been running on FS oils all of its life then please stick with it.  FS oils will not damage any of your seals, whereas Mineral Oils will.  What actually happens is that the mineral oil will attack your seals, eating them away.  Then the mineral oil will actually carbonise and ironically can act as a seal, so very cheekily covering its own back so to speak.  If your car has been running on mineral oil and then you put a good Synthetic oil in your beloved engine, you will experience oil leaks.  Sound familiar to anyone?  This is because the detergent package in FS oils is so much better that it will actually clean away all the carbon deposits exposing the actual damage the mineral oil has done, resulting in leaks.  I'm not promoting mineral oil in any way shape or form, in fact we don't even supply it, i'm simply saying that if your car has been running on mineral oil think twice before you stick FS oil in your engine thinking your doing it a favour.  In my opinion you would be better switching to a good VHVI ( Very High Viscosity Index ) oil, which some people say can perform on a comparable level with Synthetics, but like anything else you can get good ones and bad ones.  I'm sure Simon could help further if you're confused or unsure. 

However, if your car has been running on fully synthetic since day one then stick with it.  I drive an M3 and use Fully Synthetic 5w/40 all year round, I don't think we suffer from extreme climate changes to need to switch grades in summer and winter.

Finally can I again promote the work Simon does here, I'm sure it can be time consuming and he definetly deserves a beer .

It was very nice to electronically meet you Simon, it isn't to often I meet someone that really knows their lubricants.  Don't suppose you know anywhere that sells Perfluorinated Polyether PFPE really really cheaply??  He he, didn't think so .  Thanks all, happy motoring.

 

harvard468, or stephen I guess.  Semi-Synthetic oils still contain mineral oil and therefore you still get carbonisation occuring, to what extent, who knows??  Depending on which oils, probably not very much and switching to a FS oil should be fine.  However, I often get asked this question about people wanting to switch to FS oils, my answer is always the same.  When your engine was produced it would of been vigirously tested and in the Handbook BMW will tell you the API (American Petrolium Institution ) rating of the oil which your engine requires.  Both cars M5 1994, and Z1 1990 are now over 10 years old, oil technology has advanced so much since then that you will be surprised of how many oils will be suitable for your engine, the best oil 10 years ago will just be a mediocre oil in the current time.  The most important thing is that you use a an oil with at least the same API rating as the handbook says, or better.  With regards to changing up to FS oils, weigh it up.  It will protect better than SS but is it overkill, does the price justify the cost?  If you were driving a new M5 or Z4 I would be telling you to use FS oil and nothing else, but the fact remains that you probably won't really see any benefit in cars that old.

Derek M5 wrote: I've a 1994 E34 3.8 M5 with 122k and no mods, was advised that Castrol Magnatec was best suited to the engine/mileage. Especially as these engines seem to drink oil - handbook says roughly 1 litre per 1,000 miles - I normally get around 1,200 before needing to top up but worry that changing to a lighter oil would increase this usage. Any suggestions?

Derek,

You should be using somewhere around 10w-40 or 5w-40. For all year round use, BMW recomend a 5w-40. However if you are concerned about high milage stick with a 10w-40 or 10w-50. You can go fully or semi synthetic.

Moving to a thinner grade oil should not increase oil consumption as long it is a good quality shear stable oil whith quite a high flash point. However high mileage engines can some times leak a little if moved to a thinner grade oil.

Hope this helps.

Cheers

Ps. Belfast Brian welcome, its nice to have another oilman around!! We are few and far between. I hope we can do some work together on this forum.

 

Please advise on oil grade for this car:

BMW 316i, petrol, E36 1992, 82K. currently using 20w/50 but not sure if mineral/ss/fs.

Also, I drive quite often to southern europe especially in summers where temperatures can reach sometimes the 100s Cel.

Thanks

Rachid

Thewidget wrote: Please advise on oil grade for this car: BMW 316i, petrol, E36 1992, 82K. currently using 20w/50 but not sure if mineral/ss/fs. Also, I drive quite often to southern europe especially in summers where temperatures can reach sometimes the 100s Cel. Thanks Rachid

 

Hi Rachid, I would say that if you are driving to southern Europe quite often then a 20w/50 would be fine, 20w/50 is generally recommended for engines working at hotter temps.  If I was being fussy I would say that you should maybe look at using a 10w/50, because obviously driving in the UK is colder, and using a 10w/50 would put your engine under less stress in colder weather.  With regards as to whether it is mineral / ss / fs, it is likely to be FS or SS.  Hope this helps.

Oilman,

I thought it would be best to ask you.

I've got an MGF VVC (which I am selling at the mo), and am a member of a Rover forum too (Used to have a Coupe turbo). It seems that some are saying not to use a fully synthetic oil in a Rover K-series engine, but I cannot grasp why this is. I use Mobil 1 in the MGF and it has been fine, infact smoother and better than the semi-synth it had in previously.

can you shed any light, because I can't see any reason why a fully-synth would have a detrimental affect?

Thanks for that!

Its just that some say that Powertrain who make the K-series engine recommend semi. I tink it could be a case of them saying use semi and that will be fine, but further done the line its become only use semi.

agremlin wrote: Can you please recommend the oil I should use for this car: M5 1990 (E34), 3.6l petrol, no mods, approx 160k miles, engine rebuilt at 80k The guy who sold it to me said to use Valvoline Sport which I can't find locally.  Tried Havoline something and it all blew out in a week.  Using Castrol GTX High Mileage at the moment and oil consumption is much lower then before. Thanks

BMW recomend for all year round use a 5w-40 full syntheic to the spec of ACEA A3. I would personally always go for a BMW approved oil.

The Castrol GTX you are currently using is just a multigrade mineral oil and you could do much better.

E-mail me for a list and prices of BMW approved oils for your car.

Tech specs here http://www.opieoils.co.uk/lubricants.htm

Cheers

Simon.

Placed my order for oil with Simon last Thursday and asked for it to be delivered today.

8:15 this morning it arrived.

Great service, thank you.