Diesel and petrol engine oil.. .whats the difference?

[Lankytim]

I sometimes have access to diesel engine oil for HGVs and buses but i've never used it in any of my clunkers because they are all petrol.Its got me thinking though. Would the world explode if I put some 15/40 diesel oil into my petrol powered Audi? It may be a little thin for the Allegro and may completely ruin the Volvo 940 Turbo. Has anyone had any bad experiences of using the wrong type of oil?

[Tayne]

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[Richard]

The API spec tells you what level the oil has been tested at. Usually it will be quoted as something like SJ/CF. S is the specification for petrol engines, with the second letter being the revision level and C is for diesel engines.

 

I'm pretty sure you will be fine if your truck oil is API SF or better- as long as it is the correct grade. I rarely use "diesel" oil in my diesels and I've never had a problem.

 

There's a comprehensive explanation here, though you're probably as well to scroll down to the table at the bottom.

 

http://www.carbibles.com/engineoil_bible.html

[Station]

I used diesel oil in petrol engine before, as on the back it said 'suitable for diesel and petrol engines', even though it was 'engine oil for diesels' on the front.

[Lankytim]

Cheers for that link. I hadn't seen it before and its very educational! The oil im looking at is CI-4. The site says this about it...

CI-4 Current Introduced in 2002 for high-speed four-stroke engines. Designed to meet 2004 exhaust emission standards implemented in 2002. CI-4 oils are formulated to sustain engine durability where exhaust gas recirculation (EGR) is used and are intented for use with diesel fuels ranging in sulphur content up to 0.5% weight. Can be used in place of CD, CE, CF-4, CG-4 and CH-4Read more: http://www.carbibles.com/engineoil_bibl ... z0nhxa8KzO

There isnt a petrol equivalent so ive no idea if it could be used in an old Audi petrol engine or similar. I dont like the sulphur bit either. The site also says that the added detergents in diesel oils can overclean petrol engines, meaning that built up crud can get flushed into places you dont want them to be. Personally id risk it though...

[red5]

Apart from the actual grade/visc it's basically the detergents. Generally ok though - unless you really have got compression courtesy of piston ring clag you should be ok. If you haven't, or don't know, then you soon will.

[Owain-328i]

As said above should be fine, main difference is diesel oils have higher levels of detergents in them, some people use it because of this very reason every 3rd oil change as a sort of long term flush in their petrol engines to keep them clean, or clean them out.

[Mr_Bo11ox]

I wouldnt think twice about using diesel oil in a petrol. generally diesels give their oil a harder time than petrols, i would say go for it. You defo wont do any harm putting it in an oldskool non-turbo petrol engine. In fact my crab has a sumpful of diesel oil, so i'm not just talking the talk i'm walking the walk as well.

[FredTransit]

Same here, I would put diesel oil in a petrol, but not the other way round. We buy any old toot for the petrols from Asda, but the diesel oil comes a bit dearer from the motor factors.

[Richard]

There isnt a petrol equivalent

Do you mean in the table? I don't think the S and C ratings go hand in hand, it's just that the C one has been revised more often.

 

Most oils are labelled with an S rating and a C rating. Since your oil is aimed at the commercial market it might not have an S rating, but that doesn't mean it wouldn't achieve one if it was presented for testing.

 

As for not using petrol oil in a diesel- if its C rating is high enough for your engine I don't see why not.

[wuvvum]

A while back my local Tesco garage had diesel 15W40 reduced to £6 for four litres, so that's what went in all the motors, petrol or diesel, for about six months, and I never had any problems.

[Lankytim]

Cheers for the info guys, ill follow up this cheap oil and see what happens. I could end up with alot of it though.

[FredTransit]

Don't keep it to yourself then!