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Engine Oils 5w30 10w40 - Does It Really Matter?


Nikstryker
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I have had this discussion with a few friends who agree that it doesnt matter a jot in real life what oil you put in your car.

The only time it would matter is in countries that are very cold apparently.
Our pal tells us it is just a gimmick by the petrol companies to increase their profits.
We had quite a "discussion" over a few beers and things got a bit serious.
To demonstrate this I had a £100 bet with our pal Frank who is incidentally a 30 years Ford mechanic so he drained and filled up his Fiesta MK7 1.2 Ecoboost with 10W40 when it should be 5W30 I believe and he has been driving it for over a year now with no problems so it looks like we lost the bet?

What are your experiences and thoughts on this - Am I really wrong and do I owe him £100?
From looking on the internet it does seem like he is right!

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is a year long enough? how many miles?.   How do we know if it will wear out the engine or the turbo 30k miles earlier than it would have done with the correct oil. We might not know for 10years. And even then we would not really know as there are not two identical cars testing the different oils simultaneously doing the same journey and being started in the same cold places early mornings in winter etc and if one did fail earlier it might have been due to lower standard of manufactured parts in the engine and not the oil.

I don't think his test can posssibly be regarded as proof.

I don't know if it makes a difference or not, if I have a decent car I am not going to chance it.  When I was younger I had cars that were worth £250 and needed the oil topping up frequently. On those cars I would just use the cheapest oil as not much to lose if it did make a difference.

 

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I get your drift but what he is trying to prove is that the folks who say putting the wrong oil in is akin to putting diesel in a petrol car.

It came about because apparently some garages just fling in any old oil without actually checking the engine requirements.
I had a pal who was an apprentice at quikfit and he said that was the tip of the iceberg on the kinda things they do to save money and increase
profits and I have actually experienced it on a full service when they didnt even replace the engine oil - some of us know how to use the tippex fraud
technique and the stuff i recorded them saying - my advice - get a usb voice recorder with a 64gb memory card and leave it running in a hidden place in your engine
and you will hear what car mechanics really say when you are getting an MOT - Utterly disgraceful - I am going to put it up on youtube !

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I get your drift but what he is trying to prove is that the folks who say putting the wrong oil in is akin to putting diesel in a petrol car.
It came about because apparently some garages just fling in any old oil without actually checking the engine requirements.
I had a pal who was an apprentice at quikfit and he said that was the tip of the iceberg on the kinda things they do to save money and increase
profits and I have actually experienced it on a full service when they didnt even replace the engine oil - some of us know how to use the tippex fraud
technique and the stuff i recorded them saying - my advice - get a usb voice recorder with a 64gb memory card and leave it running in a hidden place in your engine
and you will hear what car mechanics really say when you are getting an MOT - Utterly disgraceful - I am going to put it up on youtube !
I once had an argument with a mechanic over the correct oil for my car.

He made the mistake of saying "Your car isn't good enough for castrol" and then tripped himself up when I asked would he say that if I owned a VW. I proceeded to call him a ***** head and put the phone down on him.

I do only use main dealers after a incident over a timing belt on my mk6 Fiesta a few years ago.

I've always used 5w 30 in any of my fords with zetec engines. Ford should know what oil their engines need.

I've always had a massive issue with "older" mechanics who think they know it all and don't like being told when they're wrong.

Back to OP. Let him have engine and turbo failure as a tech he should know better. The oil pick up will eventually sludge up because the oil is too thick. Which will inevitably starve the engine of oil and then cause the engine to seize. That's if the turbo isn't oil starved sooner.



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I'm an "older" tech and don't mind being told I'm wrong. Lol
And I don't know it all, well nearly. Ha ha

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3 minutes ago, iantt said:

I'm an "older" tech and don't mind being told I'm wrong. Lol
And I don't know it all, well nearly. Ha ha

I didn't mean all 😂 just some. 

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Lol Frank works for a main Ford dealer lol
And he is older dlol!

According to other sources there will be no difference in using 10w40 as opposed to 5w30 so it looks like i lose £100.
And the garage that ripped me  off was a main dealer!!

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Lol Frank works for a main Ford dealer lol And he is older dlol!

According to other sources there will be no difference in using 10w40 as opposed to 5w30 so it looks like i lose £100.

And the garage that ripped me  off was a main dealer!!

 

If I found out he had put 10/40 in mine I'd kick off and he'd be losing his job. Sorry, but ford say 5/30 and he has no right to claim otherwise.  

If he wants to ruin his own car, that's his problem.

 

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Yes, it matters which oil is used because the engines are ‘close tolerance’ engines so the correct viscosity of oil has to be used so that when the engine is cold the oil can easily get into the correct places.

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All this talk of 5w-30 v 5w-40 but in fact the Ecoboost engine uses 5w-20 oil.

 

The trend for thinner oils comes from the fact that an engine running on thinner oil is more economical and less polluting.

As for cold starting, it doesn't make a difference if the oil is 5w-20, 5w-30, or 5w40 because its the number before the w which represents the cold start viscosity and that is the same for those three oils. The number after the w ( 20/30/40) is the viscosity when hot. 

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Modern engines are manufactured to remarkable tolerances, and are intended to have oil of a certain kinematic viscosity at any given engine temperature, and it will be needed to maintain a particular film thickness.

 

At best you risk accelerated wear, at worst a few engines are prone to catastrophic early failure (DV6, Peugeot EW12 being two examples that spring to mind).  Your chums three pot may not have exploded, but it will be wearing at an accelerated rate.  A before and after compression test and analysis of tailpipe deposits would be far more telling than just waiting for it to explode.

 

It amazes me that people will spend thousands buying a car, and then begrudge paying an extra fiver for the correct oil.

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12 minutes ago, iantt said:

and 5w20 ecoboost castrol oil is only £25 for 5 litres.

 

 

That's not too bad. I use Millers 5w-20 for our two ecoboost Fiestas and I paid £96 for 20 litres. Where do you you get the Castrol 5w-20 for £25 ?

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1 hour ago, Jethro_Tull said:

Modern engines are manufactured to remarkable tolerances, and are intended to have oil of a certain kinematic viscosity at any given engine temperature, and it will be needed to maintain a particular film thickness.

 

At best you risk accelerated wear, at worst a few engines are prone to catastrophic early failure (DV6, Peugeot EW12 being two examples that spring to mind).  Your chums three pot may not have exploded, but it will be wearing at an accelerated rate.  A before and after compression test and analysis of tailpipe deposits would be far more telling than just waiting for it to explode.

 

It amazes me that people will spend thousands buying a car, and then begrudge paying an extra fiver for the correct oil.

Yeah true Jethro i would never put anything less than the right stuff in my relatively new car just in case.
So you reckon I am £100 sovs up then - i shalluse your post as evidence lol

My older cars i am not too bothered but as there is no leaded petrol now my Lotus is sitting idle for the last 10 years.

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You're probably not going to see your hundred nicker I'm afraid without some extremely thorough before and after inspection on the engine.  On the plus side, you can feel safe in the knowledge that you were right.  

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Does it taste like it came fresh from the Gulf of Mexico? :crazy:

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I didn't taste it, I'm more refined than that.lol

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I don't think there is any doubt that there is fake oil out there being sold. I don't know how you would tell if it was fake or genuine.  I have always bought Castrol magnetec from tesco or asda when it is only special offer as I feel it is less likely they would be selling fake.

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