My dealer used semi-synthetic oil... Is that OK?

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Hello everyone, I was wondering what your thoughts are on this...

Just before I picked up my car after its 1st service had been carried out, I asked the person who was preparing my invoice if they used fully-synthetic oil. He said yes. (but of course he would)

I then asked if he could write for me on a piece of paper what brand and type they use, just for reference, if I ever needed to get some. He looked at the computer screen and wrote it down. I read it and it said Castrol Magnatec 10W-40. Now, I happened to use this exact same oil in my previous car, and I knew it was semi-synth. I told him that, and he went to ask someone else, and then came back telling me I was in fact right about that. So I asked him, isn't 10k miles too many for a semi-synth oil? I'll let you guess what he replied...

So, what do you think? What oil do your dealers use?

P.S.: I had a quick look at the dipstick when I got home from the dealer and the oil did look brand new. But after only a couple of days' use, it has already started to go darker, which is rather unusual.

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Find out if the magnatec meets whatever VW oil standard that is stated in your cars manual.

If it does not then the answer is no, if it does then the answer is yes.

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Find out if the magnatec meets whatever VW oil standard that is stated in your cars manual.

If it does not then the answer is no, if it does then the answer is yes.

This oil is VW 505

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Manual says either of the following: (for petrol engines)

VW 501 01

VW 502 00

VW 504 00

Magnatec 10W-40 meets VW 501 01, no complaints there.

But isn't 10k miles too many for a semi-synthetic oil? I thought fully-synthetic was the only way to go with cars nowadays.

Thank you very much for your replies! I appreciate it.

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my local dealer's use 15-40, probably the cheapest stuff they can get. But the vag specialist uses 5-30. My previous car 1.2 12v 55reg had 10-40.

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Found out recently that VW 505.01 spec can be found in Semi-Synthetic OR Fully Synthetic.!! (SEE ATTACHED PHOTOS)

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On a new (ish) car I would insist any dealer or garage used the highest spec oil as approved by VAG. Namely any full synthetic oil that met the VAG spec 504 for petrol engines or VAG spec 507 for diesels ( with or without DPF) .

One such oil is Mobil #1 "esp" 5W-30 full synthetic VAG 504 & VAG 507 approved.

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Thanks everyone! Indeed, it seems dealers will go for the cheapest stuff they can get away with. At least I am relieved to know that mine uses Castrol, a brand I trust a lot.

Still, what's your opinion on the longevity of semi-synthetic oils? Good enough for 10k?

I'm only asking because I am considering changing the oil myself halfway before the next service. I reckon 5k miles is way better on semi-synth, but that's just me. Checking the dipstick with the factory fill since I first got the car, I noticed the oil stayed very clean and clear for thousands of miles, which leads me to believe that the factory used fully-synth.

I'm taking into account that the effects of skimping on the quality of the oil now will probably be obvious in the future, long after the warranty is finished. Therefore, dealers will never have to deal with engine wear after 100k miles, so it probably makes sense for them to use the cheapest oil possible.

I, however, would like to have a car that will give me at least 250k, before it starts using oil. That's why I'm so fussed...

Thanks again!

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Fabia VRS 10,000miles / 12 months, depending which comes first, it being fixed servicing period type.

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Before the widespread use of fully synthetic oils, semis were being used with 12k service intervals. Its the VAG code Id be concerened with. My dealer said they used a semi and when I questioned it they said oh no it is a fully synthetic! Ill never know I guess.

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Cheers all!

I suppose modern oils last longer and longer, maybe I am being too anal. I guess I'll have a good thorough look at the condition and colour of the oil at 15k miles, and make a decision then if an extra oil change is worth the effort. Seeing as it takes less than 3 litres of the stuff, a DIY job will be dead cheap.

By the way, always check the level when you get your car back after a service from the dealer!!!

I checked mine yesterday, as I do every Saturday, and they had overfilled it! About an inch over the MAX!!!!!

Had to spend the best part of an hour yesterday draining some out of the sump, and trying to get the level where it should be. A lot of guesswork as to how much to let out, it included raising the car several times to get underneath it, and dropping it flat again to check level. Not pleasant, I tell you!

Edited by FAB59

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Cheers all!

I suppose modern oils last longer and longer, maybe I am being too anal. I guess I'll have a good thorough look at the condition and colour of the oil at 15k miles, and make a decision then if an extra oil change is worth the effort. Seeing as it takes less than 3 litres of the stuff, a DIY job will be dead cheap.

By the way, always check the level when you get your car back after a service from the dealer!!!

I checked mine yesterday, as I do every Saturday, and they had overfilled it! About an inch over the MAX!!!!!

Had to spend the best part of an hour yesterday draining some out of the sump, and trying to get the level where it should be. A lot of guesswork as to how much to let out, it included raising the car several times to get underneath it, and dropping it flat again to check level. Not pleasant, I tell you!

" look at the condition .... make a decision .." Sounds very scientific !

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Thanks everyone! Indeed, it seems dealers will go for the cheapest stuff they can get away with. At least I am relieved to know that mine uses Castrol, a brand I trust a lot.

Still, what's your opinion on the longevity of semi-synthetic oils? Good enough for 10k?

I'm only asking because I am considering changing the oil myself halfway before the next service. I reckon 5k miles is way better on semi-synth, but that's just me. Checking the dipstick with the factory fill since I first got the car, I noticed the oil stayed very clean and clear for thousands of miles, which leads me to believe that the factory used fully-synth.

I'm taking into account that the effects of skimping on the quality of the oil now will probably be obvious in the future, long after the warranty is finished. Therefore, dealers will never have to deal with engine wear after 100k miles, so it probably makes sense for them to use the cheapest oil possible.

I, however, would like to have a car that will give me at least 250k, before it starts using oil. That's why I'm so fussed...

Thanks again!

10k is fine for a semi synthetic. As mentioned before always make sure it meets the current vag spec which is 504/507 which includes 505.

If however you do lots of short runs then i would suggest changing twice a year.

What color the oil is after x amount of miles is irrelevant. Oil contains calcium and phosphur/sulphur based additives and detergents which are there to suspend the dirt which gives it that dirt appearance. How dirty the oil gets can be down to other factors including:

how clogged your air filter is

the dust/dirt levels

time of year

A brand new car with new oil will probably run cleaner than say one that has done many more miles. This is natural.

The difference between a semi and fully is additives and base oils. Mostly with semi they use mineral bases as opposed to synthetic.

Edited by newskoda

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Thanks newskoda. You're probably right. I was just a bit concerned because I've been using the same oil that the dealer used, in my last car, for years. After every oil change it would stay really clean for at least 2k miles.

Anyway, it just occured to me that garages are usually rather hasty when draining the old stuff, so they must have left some tiny amount in, which could be just enough to affect the colour of the new oil when mixed up.

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" look at the condition .... make a decision .." Sounds very scientific !

I am but a humble automotive engineer who specializes in Vehicle Dynamics. Tribology was one of my worst subjects in uni.

If you're any good at it, feel free to enlighten me...

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