Just had to buy some engine oil. First off, when I had a petrol car I never had to put oil in the engine. I now have a 3 litre diesel that needs oil every 6 months – it's only 3 years old and I do about 10k a year.

Thing is, I see oil at 15 quid a litre and also at 8 quid what's the difference? Which to buy. Also what does the labelling mean '10w – 40' or '10w – 30'.

It's 2010 and we are still having to put oil in engines?

Next time it's a Toyota not some over rated German brand.

http://www.upmpg.com/tech_articles/motoroil_viscosity/index.html

you do realise the petrol car had oil in it too?

http://www.upmpg.com/tech_articles/motoroil_viscosity/index.html

Now I am confused. 😯

Must admit that the link isn't the easiest read!

Best thing to do is look in your cars handbook for the recommended grade of oil,or failing that,any decent car accessory shop worth its salt will be able to advise on what oil to use with the help of a manufacturers chart.

As a time served mechanic for the local authority I would only use quality oil recommended by the engine maker,not necacerally the car manufacturer!

Diesels do use oil,using the wrong spec oil,coolant can cause serious problems for long term reliability.

Engine oil is designed to create a barrier between all moving parts in your engine,most wear occurs as the engine is started.
The 10w 40 is the minimum spec required for your engine,and will give maximum protection at a given temperature (for example sustained motorway driving)