Went to Halfords to look for some oil today and I can’t quite believe how many different choices there are.
All their own brand stuff is marked for different makes (Mercedes, VW , Ford etc). They’re all different prices which has made me wonder what actual differences there are in the makeup of the oil? Is it simply that different car manufacturers have different standards when it comes to oil used for their cars?

Yes.

Many manufacturers make oil specifications for their cars. There is also a default industry specification called API-SM with the last letter increasing every time they bring out a new one.

VW for example have 504.00/507.00 for my car which means it meets the special lubricity requirements for the camshaft driven injectors and for long life. The Prius on the the other hand only requires API-SM.

Your manual will tell you what your car needs, and the back of the oil bottle will tell you what spec it meets. Often more than one.

Simple.

Making sure any oil is the right specification (SAE) for your engine is key, after that its down to how deep your pocket is,I would say coolant is often the most miss understood liquid in your engine in terms of long term trouble free ownership,Get this wrong and it can get very expensive as internal parts corrode due to the wrong type of inhibitors to gasket/metals (used in the engine) are used.

If all the Halfords oils are different specs, why does the booklet in store also recommend a Castrol alternative that seems to be the same for loads of cars?
Is this oil of superior quality so suits more than one make, and if it is, how come the last time I bought some it was cheaper than the Halfords one?

I just buy oil from the local independent auto factor – their cheap version which is specific to my car. Cheaper than anything Halfords sells.

so does the local garage carry 50 odd types of oil?

If all the Halfords oils are different specs, why does the booklet in store also recommend a Castrol alternative that seems to be the same for loads of cars?

Because one oil can meet lots of specs. Check the label, it should list them all.

Halfords were doing 4 litres of their own fully synthetic for 12 quid last week. I bought 12 litres of ford oil to service two cars. It is made to ford spec and I’ve used it for years without issue.

For that price you can’t argue

That’s really why I asked. I saw the oils for £12 and wondered if they were that inferior that I couldn’t put them in my Peugeot van?

Nah special price. The 5 lites normally retail at 30-35 notes iirc.

Bought 4x 4l at £12, data sheet shows its made by Comma, meets the Ford spec for my Tdci transit which has been run on Comma Xtech for years without issue although I do change it every 5k miles

There are very few manufacturers of the actual oil, as long as they’re the right spec there’ll be little difference.
Where there is a lot of difference is in the additive packs used in the oil, which is why some are so much more expensive.

Basically, if you want the best oil for your fancy sports car that you intend to keep til death, spend the extra on a proper poly alpha olefin or ester based fully synth (I used to use Silkolene on recommendation of my oily boffin friend), if you’re just chucking it in the daily snotter, go for the cheap stuff in the right spec.

Basically, if you want the best oil for your fancy sports car that you intend to keep til death, spend the extra on a proper poly alpha olefin or ester based fully synth

Interestingly there’s an argument that fully synth is bad for some engines applications.
We have a boat with a Honda 225hp v6 outboard – pretty high performance engine that works hard (engine pushing a boat through the water is the equivalent of a car always going up hill). I’d have thought that fully synth was the way to go but it seems that it’s better to go with a non-fully synthetic oil for these applications as the extra cooling of fully-synth is not good for the engine.
Seeing as the oil is changed every 50 hours max also means that fully-synth would be a waste.