Engine Oil

[vyv_cox]

I have to say I like the look of API CI, it is formulated for low sulphur diesel and is mineral based. Its TBN is higher than I would prefer for a lightly loaded engine but is comparable to some versions of API CF, which many use. If I could buy it in Greece I could be tempted to try it but fortunately API CD is readily available here.

 

[theoldsalt]

Mineral/conventional oils break down under pressure and temperature and their chemical composition changes with time much faster than synthetic oils. Also, synthetic oils have additives to remove deposit compounds. The oil molecules of mineral oils is larger in size which helps to "bridge" the gaps between moving metal, however, although the synthetic oil molecules are smaller, they do not break down and maintain lubricating ability under wider conditions. Some will argue that the additive detergents encourage carbon particulates to contaminate the oil, however, it has not been demonstrated in practice. Oils (mineral) in the 70's were very poor in comparison to synthetic oils, breaking down easily, causing huge problems with aero piston engines, being air cooled were operating at higher temperatures. We can not expect manufactures of older engines/models to review and subsequently to change the oil specification and I dont suggest that others should use synthetic oils for their older engines. The reason I change oil is because older engines will contaminate the oil much quicker due to larger clearances between pistons and cylinder, hence diluting the oil with small amounts of diesel, also the cost is very small, as synthetic oils are the same price as good mineral oils. In additional, a cold engine with synthetic oil will start easier, with less strain. And again, I dont suggest that older engines should use synthetic oil, I simply explain why I use synthetic oil on my old engine.

Your explanation appears to completely disregard oil compatibility with seal material.

 

[lw395]

Your explanation appears to completely disregard oil compatibility with seal material.

Unless your engine contains bits of sealskin, that's unlikely to be a problem!
(that is a semi serious point, the real problems with synth oil hosing out of old engines go back to 'seals' and gaskets made out of leather and cork.
If anyone is really interested in synth oils, DYOR. This forum is a branch of the church of CD 10w30.
Mobil 1 is 40 years old now!

 

[RichardS]

Unless your engine contains bits of sealskin, that's unlikely to be a problem!
(that is a semi serious point, the real problems with synth oil hosing out of old engines go back to 'seals' and gaskets made out of leather and cork.
If anyone is really interested in synth oils, DYOR. This forum is a branch of the church of CD 10w30.
Mobil 1 is 40 years old now!

All very true! I started using Mobil 1 - the first synthetic available - in 1978 when it first appeared. It was painfully expensive. I'm guessing £100 for 5L at current day inflation but it came with a booklet saying that after testing Mobil could confirm that you could quadruple the oil change interval compared to any other oil (all other oils were mineral, of course) whilst retaining the recommended filter change interval. That claim has been dropped now but I believe for purely commercial reasons rather than technical.

The furthest I have ever pushed the oil change was about 3x interval but the oil comes out cleaner that a mineral oil at 1x.

I stripped down the top end of my old 19 year old Jag a few weeks ago. It's only ever been run on Mobil 1 with a 2x change interval. The castings and bearing faces look as if they have just left the production line. No brown deposits, no discoloration, no scoring anywhere. I haven't used 100% mineral oil in any application (bikes, cars, boats, outboards, lawnmowers) since 1978!

Richard