A friend of mine, (oil sheik at Q8) tells me that oil for diesel vs petrol motors is the same.

With a little Googling, this comes to light, so it ain't all bad after all!

"It is possible for an oil to conform to both the gasoline and diesel standards. In fact, it is the norm for all diesel rated engine oils to carry the 'corresponding' gasoline specification. For example, API CJ-4 will almost always list either SL or SM, API CI-4 with SL, API CH-4 with SJ, and so on."

personally i think oil is oil, and some happens to be used for petrol and some for diesel, i dont think at any stage oil was designed not to be used in a petrol engine and oinly diesel, correct me please if im wrong but only a thought

this is what i have got

running the cheapest 20/50 I can find here. Meant to change it for something thinner before winter set in, but I hadn't got around to it before the current cold snap started. It's started on the first turn at 7.30 every morning so far, so coupled with a gentle warm-up, I don't think it's causing any problems.

Why not? Diesel engines run at way higher compression ratios than a petrol, and generate dirtier oil. Hence more detergent and higher oil film strength.

i stand corrected in my unsure statement ealier,

Please refer to my earlier (post Googling) post.
And could you explain why diesels generate dirtier oil? Is it because it's often possible to see unburnt carbon in their exhaust?
One has to ask, though - why do the manufacturers bother with separate "petrol" and "diesel" oils. To make for more shelf space in the shops?

Diesel is a heavy oil and creates more soot than petrol when it burns. Also the compression is so high more contaminents get past the piston rings. The diesel oil holds the contaminants in suspension, the oil filter can only filter out the bigger particles.

I realise it's getting a bit late over there, but - there is almost a suggestion in all of this that diesel-rated oil would be "better" to use in a petrol engine... comments?

i dont know much about engine oil, i just put in what haynes manual says and thats it really

however if the 2cv uses "diesel oil" then maybe a diesel oil is better suited in this particular petrol engine..