engine Oil

My truck runs on 15w-40 oil. So whats the modern equivalent - can i use 5w-40 synthetic safely ?

Just as background this is a 20 year old Pug/Cit/Fiat Soffim 2.5 turbo diesel engine, chain driven and the chain tensioner relies on oil pressure.

Also mixing mineral and synthetic - can i mix them safely if I'm on the road in the back of beyond and i can only get mineral oil ?

or should i just stick to mineral or semi synthetic 15w-40

i would stick to 15/40 due to cost and general availability

but if you check your hand book it will give you all the recommend oil grades you can use so you can decide what sort of tempreture ranges you are going to use the vehicle!

Don't use full synthetic as these engines were never designed to run on them.

In the UK you can run this engine on 10/40, 20/50, 15/40, and either mineral or semi synthetic oil. The internal clearances are too large for full synthetic oil and it will cause damage to the engine, semi-synthetic was designed as an interim oil which can be used in either older engines designed for mineral oils or modern engines which are designed for semi-synthetic or full-synthetic oils.

You can mix semi synthetic and mineral oils safely as its the additives which are part mineral and part synthetic and all oils have a mineral content to lubricate the engine, the additives protect the mineral content to allow it to work harder and for longer in more hostile operating conditions such as high working temperatures or under harder internal working conditions.

What is the difference between synthetic and real oil?

Basically: all oils contain mineral oil, which is less than 50% of what you get in the container of oil; the rest are additives called the additives package which prolong the life of the oil and protect your engine from its working conditions, this additive package is derived from mineral sources just as the mineral oil content is, the mineral oil and mineral package combined are pure mineral oil.

Semi synthetic oil differs only in the fact it contains less actual mineral oil content, this is because the additives package is better because it is made up of both a mineral content and synthesised content, thus semi synthetic oil; this makes the smaller mineral content last longer and work better under more harsh conditions then pure mineral oil.

Fully synthetic oil contains even less mineral oil content, this is because the additives package is even better as this contains no mineral content and is comprised of purely synthesised contents which work to better protect the smaller mineral content.

In any oil it is only the mineral content which actually lubricates the engine, not the additives package.

Film thickness is crucial as this is the thickness of the oil actually deposited on a metal surface, in comparitive terms mineral oil has quite a thick film which was designed for engines of their time which had quite sloppy tolerances due to the manufacturing equipment of their day, with the advent of modern technology and progress the engine internal clearances have actually got tighter due to better manufacturing equipment and processes. Fully synthetic oil has the thinnest film thickness and is suitable for modern engines built using the latest equipment which give much tighter internal clearances, and with such tight clearances you can only use fully synthetic oils.
Semi synthetics were derived to meet the changes during the transition from mineral oils to fully synthetic oils, they are the real trick oil which can work with the sloppy internal clearances of older engines by increasing their film thickness, or reducing their film thickness for more modern engines using full synthetics, and were designed to do just this, as well as being able to be used in hign mileage engines with wear which originally ran on full synthetic oils.

clearasmud......

Obvious innit!

just goes to show,

Turns out on our Iveco 4x4 email list we have a fuel and oil professional so his advice has been good

I bought Morris Oils 15w40 in the end as its a 'heavy duty' oil and covers the specs for quite a few truck companies and our expert says its OK

Oh the Morris Oil was also quite cheap if bought in 25 litre cans

Assassin wrote:

Basically: all oils contain mineral oil, which is less than 50% of what you get in the container of oil; the rest are additives called the additives package which prolong the life of the oil and protect your engine from its working conditions, this additive package is derived from mineral sources just as the mineral oil content is, the mineral oil and mineral package combined are pure mineral oil.

Semi synthetic oil differs only in the fact it contains less actual mineral oil content, this is because the additives package is better because it is made up of both a mineral content and synthesised content, thus semi synthetic oil; this makes the smaller mineral content last longer and work better under more harsh conditions then pure mineral oil.

Fully synthetic oil contains even less mineral oil content, this is because the additives package is even better as this contains no mineral content and is comprised of purely synthesised contents which work to better protect the smaller mineral content.

In any oil it is only the mineral content which actually lubricates the engine, not the additives package.

Film thickness is crucial as this is the thickness of the oil actually deposited on a metal surface, in comparitive terms mineral oil has quite a thick film which was designed for engines of their time which had quite sloppy tolerances due to the manufacturing equipment of their day, with the advent of modern technology and progress the engine internal clearances have actually got tighter due to better manufacturing equipment and processes. Fully synthetic oil has the thinnest film thickness and is suitable for modern engines built using the latest equipment which give much tighter internal clearances, and with such tight clearances you can only use fully synthetic oils.
Semi synthetics were derived to meet the changes during the transition from mineral oils to fully synthetic oils, they are the real trick oil which can work with the sloppy internal clearances of older engines by increasing their film thickness, or reducing their film thickness for more modern engines using full synthetics, and were designed to do just this, as well as being able to be used in hign mileage engines with wear which originally ran on full synthetic oils.

Thank you Assasin, it is enlightening