Are all 15 w40 oils the same?

[jac]

Whilst in Local sainsburys I noticed cans of Sainsburys 15w40 oil, marked as suitable for Diesel engines. It may surprise you to know that Sainsburys special offer was cheaper than local swindlery.

I didn't buy any as i have a feeliing that Marine Diesels don't get on with modern oil (i've always just bought what was in chandlers) but it set me thinking. Is their a type of oil available in the high street at high street prices which is the same as the stuff sold under the marine label?? How do we tell? The Volvo manual just says 15w40 or 20w50 so have I been too cautious ??

 

[MoodySabre]

I use 15w40 mineral oil from a local car spares place. About £16 for 5 litres. What Sainsburys sell may be synthetic as used by modern engines.

 

[Spi D]

No.
15W-40 only states the viscosity (multigrade range), nothing about properties or suitability for specific use

Oils carry a certification and must be selected to meet or exceed the recommendations in your engine manual. Oil standards are normally backwards compatible, but the base oils are different. Although better on the paper a fully synthetic oil may not be good for an old(ish) lump with wear, stiff seals or large tolerances as the oil may simply pass through.

http://en.wikipedia.org/wiki/Motor_oil#Standards

 

[macd]

jac: there's a wealth of past threads on much this topic. But to save you wading through them, try this link: http://coxengineering.sharepoint.com/Pages/Oilforyachtengines.aspx

Note in particular the stuff about API classification (which should be clearly marked on any oil you buy) and over-specification.

Vyv is a regular on these forums and used to work as a metallurgist in the oil industry. He knows of what he speaks.

 

[Avocet]

If you have the handbook for your engine, it should quote either an API classification (Like "CF" or something) and maybe an ACEA (The European equivalent) classification that the engine was designed to run on. These should b in the "small print" on the Sainsbury's oil container.

 

[prv]

As others have said - check the API letters. And yes, if they match then the cheap Sainsburys oil (cheaper the better - tends to mean older spec) is probably fine for your engine. I always ran Kindred Spirit's Yanmar lump on Halfords' cheapest oil for "old diesels".

(We currently have Volvo branded oil in the new boat's D1-30, a case of needing some in a hurry and not knowing what the proper spec was. But as has been mentioned here before, Volvo like to spec one single oil for everything from my modified dumper-truck engine to massive high-revving beasts in big mobos. Seems unlikely that the same oil would be optimum for both, and I'm sure they lean towards the big engines' needs, so in fact I can probably do better for mine by finding out the proper spec and using it instead of the branded stuff.)

Pete

 

[jac]

Does quote CD in the handbook. Looking at Vyvs site it does say that CF can be used as a replacement but I seem to remember it was synthetic so may duck out on that!

 

[Tranona]

The cheap oils are usually labled "suitable for old style diesels" or some such words and are mineral usually to CF. About £8 for 2l in Tescos, but can be got in 5l from other places for about £15. The (unsuitable) semi synthetics are usually at least 50% more.

 

[macd]

CF can be used as a replacement but I seem to remember it was synthetic so may duck out on that!

CF can be mineral or synthetic. It'll say on the can.

 

[jac]

CF can be mineral or synthetic. It'll say on the can.

Thanks. Should have made my post clearer. I believe the Sainsburys stuff was synthetic (I can see I'm going to have to go back and read the label properly! ) so think that as a synthetic version it's unsuitable.

Of course With my luck, it will probably be a mineral one and therefore suitable, just no longer on special by the time I get back. I have a feeling they had over-ordered hence the offer!

 

[vyv_cox]

If I recommend CF on the website it's time I changed it. Now that sulphur levels in diesel fuel are universally low it would be better to use CF-4, which has a lower TBN. Just checked and in fact I do say CF-4.

 

[jac]

If I recommend CF on the website it's time I changed it. Now that sulphur levels in diesel fuel are universally low it would be better to use CF-4, which has a lower TBN. Just checked and in fact I do say CF-4.

Was going by the table at the bottom where in describing CF it says can be used inplace of Cd oils, do agree though that further up it says CF-4.

So assuming is a mineral, not synthetic, is a CF ok or must it be CF-4?

 

[vyv_cox]

You will find that very many later specs say they can be used as substitutes for obsolete ones. You need to read the whole article to understand that this may be true for automotive use but not for elderly designs of yacht auxiliaries, particularly raw water cooled and particularly those that only run for a few minutes to get the boat out of its berth.

 

[Lakesailor]

 

[ithet]

Better? Says CD.

http://www.ebay.co.uk/itm/VICTORY-15W40-MINERAL-ENGINE-OIL-API-CD-SF-4-5-LTR-EXCELLENT-OIL-FOR-OLDER-CARS-/290745537609?pt=UK_Garden_Lawnmowers&hash=item43b1c8d449

 

[sailorman]

Was going by the table at the bottom where in describing CF it says can be used inplace of Cd oils, do agree though that further up it says CF-4.

So assuming is a mineral, not synthetic, is a CF ok or must it be CF-4?

it will make no difference

 

[vyv_cox]

it will make no difference

Good to know that the millions spent on research by the oil companies results in lubricants that are all exactly the same.
Even reading the generic information produced by API, shown at the bottom of my oils page, shows very clearly that CF, CF2 and CF4 must be different.

 

[Neil_Y]

Good to know that the millions spent on research by the oil companies results in lubricants that are all exactly the same.
Even reading the generic information produced by API, shown at the bottom of my oils page, shows very clearly that CF, CF2 and CF4 must be different.

I heard (but have no idea if it's just a myth) that older engines relied on more mist lubrication in wet sump engines and the old mineral oils gave better mist than the synthetics? what do make of that Vyv?

 

[vyv_cox]

I heard (but have no idea if it's just a myth) that older engines relied on more mist lubrication in wet sump engines and the old mineral oils gave better mist than the synthetics? what do make of that Vyv?

Sounds very credible, synthetics have very different wetting and droplet formation properties than minerals. Although I'm not sure how much modern engines differ from older ones when it comes to splash lubrication of cylinder bores? The difference that synthetics make to bearing temperature is incredible, we measured reductions of more than 30C on a big multistage pump, due to the way that shear acts on the oil. It seems to be laminar under load, so does not form droplets so readily.

 

[Neil_Y]

Interesting, thanks. It's nice to know why advice is given sometimes and that makes sense.