Do you understand 10w40 oil?

Doooford

What the ruddy hell is oil about?
I went to Eurocarparts (Wouldn't recommend - terrible customer service and never received order) and entered my registration number. It recommended 10W40 so I ordered 6 litres which didn't arrive.
To cut a long story short I've given up on ever seeing the order so I saw some half price Castrol GTX in Tesco so purchased 6 litres.
I've just been to the castrol site and put my Reg No. in and it recommends Edge Turbo Diesel 5W-40.
Does the type change between manufacturers? Do I need to get a refund and get another oil?
Very confused by it all... :eek:

Car is a Diesel Rover 75.

Strider590

I'll try to keep it simple, it's a rather complex issue.

10w40 is a slightly thicker (viscosity) oil than 5w40, a lower viscosity oil protects better from cold, it's also recommended for new engines with very tight tolerances, but pour it into an older engine and the piston rings will struggle to keep it out of the combustion chamber and you'll burn oil.
Too thick and it'll cause high oil pressure, blow seals, wreck the oil pump and maybe even help to cause a HG failure.

That said, the difference between 5w40 and 10w40 is minimal... But on your vehicle which is at least a few years old, I would say 10w40 will be fine and probably compliment the state of the engine quite well.

The first number is the viscosity at cold start, 5 is thinner than 10.
The second number is the viscosity index at operating temps, so at temp 40 = 40 = the same.

Cold start.
A 5w-40 will flow better than a 10w-40.
A 10w-50 will flow better than a 15w-50
A 5w-40 is the same as a 5w-30
At operating temperatures.
A 10w-50 is thicker than a 10w-40.
A 15w-50 is thicker than a 5w-40
A 0w-40 is the same as a 10w-40

Interestingly, race cars (especially the classics) tend to use very thick oil (hmmm can't beat the smell of Castrol-R), thick oil is crap at low temps, but at high temp it protects better that anything else where low viscosity oil would be as useful a bucket of water in your engine.

garethgas

Unfortunately, oil isn't what it used to be. Gone are the days of Duckhams 20/50 in everything.
The two numbers refer to the viscosity (or thickness) of the oil when hot/cold.
Just to confuse matters, manufacturers now specify a whole different range of oils for their cars.
Some put any old stuff in but I think their taking an unecessary risk.
My view is to put the manufacturer's specified oil in so that you know its right.

Doooford

That makes alot of sense. Just confused as to why Castrol would recommend something different. My Haynes book says 10W40 so I'll stick with that.
Is the fact that Castrol recommend an oil specific to a Turbo Diesel to do with additives?

oldagetraveller

"hmmm can't beat the smell of Castrol-R".
Agreed, I remember years ago many people used to add a small amount of Castor Oil to their fuel tank to replicate this! Not me, honest.
On a different note, Strider, I did eventually sort out the date/time thing on the mini dvr camera! Mostly due to your help. So thanks again for your time and patience.

CHR15

It's a Rover 75 !! you could put Fry's Crisp 'n' Dry in it and see no difference.

Doooford

CHR15 wrote: »

It's a Rover 75 !! you could put Fry's Crisp 'n' Dry in it and see no difference.

:rotfl:This is exactly what I really wanted to hear. Didn't want to get worried about the difference in 5W and 10W. Just wanted a "Just whack it in mate".

THanks CHR1S for you confident "get on with it" attitude! :beer:

RichGold

CHR15 wrote: »

It's a Rover 75 !! you could put Fry's Crisp 'n' Dry in it and see no difference.

A couple of years ago a friend used to give me a lift home from the pub he worked at if I was still there at closing time. It started as a joke but I used to buy him a bottle of crisp and dry for the lift. I don't think he was putting it in with the oil though.

I always wondered why that van smelt of chips

forgotmyname

If it doesnt turn over in the winter you will know you should have gone for the 5-40 and not the 10-40.

Im sure if it gets that cold the oil in the engine will be the last thing on your mind though.

bigjl

You do reakise that because somebody ob a forum tells tlyou to bung it in will make little difference to who pays for the damage and wear caused by the wrong oil.

Your Rover 75 uses a BMW engine not a Kseries.

You have bought the wrong oil your GTX is only good for older petrol cars mainly, perfect for my mates Cavalier.

But not perfect for a BMW turbo diesel engine with a camchain.

bigjl

CHR15 wrote: »

It's a Rover 75 !! you could put Fry's Crisp 'n' Dry in it and see no difference.

Would you give the same misleading advice if the owner of said diesel engine had it under the bonnet of a 5series, 3series or Freelander?

From what i have been led to believe these engines take fully synthetic oil only.

My Omega with the 2.5 BMW lump was also fully synthetic only.

My Mondeo tdci has been run on top spec oil, no.issues at well over 160k.

My previous Legacy was run on fully synthetic oil and never gave me any trouble.

I would think Castrol know more about their products than Haynes or posters on an internet forum.

You are aware that GTX is no longer the leading edge of oil technology that it was in the early eighties don't you?