# Is 5w50 Mobil 1 fully synthetic oil bad for my car?



## Robby (Mar 1, 2013)

Be prepared for lots of opinions.
IMO, in particular with your climate, it will be just fine.....but, 5w30 would be fine too.....as long as both are synthetic.

The quantity is, for the 1.4T in this country, 1.25 gl....if you have the same engine this tiny bit of additional oil is of no consequence.
I'm on the other side of capacity.....I only put in 4 qts at change.

Rob


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## armobarak (Jun 25, 2014)

Robby said:


> Be prepared for lots of opinions.
> IMO, in particular with your climate, it will be just fine.....but, 5w30 would be fine too.....as long as both are synthetic.
> 
> The quantity is, for the 1.4T in this country, 1.25 gl....if you have the same engine this tiny bit of additional oil is of no consequence.
> ...


Average temperature here in the summer is 28-36 Celcius ( 85-100 F) , some say that the 5w50 is too thick at this temperature so it can harm the engine..

My motor is 1600 cc ecotech gas engine


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## David1 (Sep 16, 2011)

It may be to thick when the oil is hot to flow properly. The cam phasers for the valve timing are designed for a specific flow rate and the thicker oil can slow that down. I will tell you that on my bmw the Mobil 1 0w-40 is a recomended oil and has the same properties as the BMW castrol 0w-30. Most of the Mobil One family runs a little less hot viscosity. My 335 holds 7 quarts and if I substitute about 4 quarts of that with BMW's TWS oil which is a 10w-60 (for the M cars) I get cam timing errors because it is to thick. Also, if the oil is to thick, it can not flow quick enough to carry the engines heat away in todays tighter tolarance built motors. Your fuel economy can also suffer because of the extra energy needed to pump the thicker oil around.


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## armobarak (Jun 25, 2014)

Well is that thickness harmful to the extent that i should replace that oil *now* and not wait for the scheduled usage (6000 miles)???


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## jalaner (Dec 28, 2013)

My experience is that 100% synthetic oil causes leakage and seepage in both internal and external engine seals. 1984 Audi GT Coupe-switched from conventional to Mobil 1 5w30 at first oil change. 2 days later noticed smoke from under the hood. Valve cover gaskets were leaking so much that oil was puddling on the top of the engine. Replaced gaskets and switched back to conventional but oil continued to slowly seep from all engine seals until I sold it. 1998 Cadillac Deville-changed from conventional to Mobil 1 5w30 at 40K miles. Oil began to seep from valve cover gaskets and main seals. Repaired valve cover gaskets and changed back to conventional but main seal repairs were too expensive. Internal engine seals were eventually damaged causing low oil pressure warnings at idle. The same Cadillac dealer who recommended the synthetic now recommended switching to 20w50 to temporarily stop the low pressure warning and sell the car, which I did. 2001 BMW 740i-100% synthetic is OE. No problem for 20K miles. Since then replaced valve cover gaskets twice, $700 each. At 70K miles slow, cosmetic, seepage at both main oil seals. Repair costs will approach the value of the car so I just put up with the occasional oil odors. I have a Pontiac Vibe that uses conventional oil. At 50K miles I have never had a repair, all seals are dry. 2014 CTD- 5K miles, no problems yet. Each time I installed synthetic I was assured that seals were designed for it. I've been driving since 1970 and have never had an engine repair from wear, the standard sales pitch justifying the additional synthetic cost. 100% synthetic oil is just a big, expensive scam and I will avoid it when possible.


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## XtremeRevolution (Jan 19, 2012)

jalaner said:


> My experience is that 100% synthetic oil causes leakage and seepage in both internal and external engine seals. 1984 Audi GT Coupe-switched from conventional to Mobil 1 5w30 at first oil change. 2 days later noticed smoke from under the hood. Valve cover gaskets were leaking so much that oil was puddling on the top of the engine. Replaced gaskets and switched back to conventional but oil continued to slowly seep from all engine seals until I sold it. 1998 Cadillac Deville-changed from conventional to Mobil 1 5w30 at 40K miles. Oil began to seep from valve cover gaskets and main seals. Repaired valve cover gaskets and changed back to conventional but main seal repairs were too expensive. Internal engine seals were eventually damaged causing low oil pressure warnings at idle. The same Cadillac dealer who recommended the synthetic now recommended switching to 20w50 to temporarily stop the low pressure warning and sell the car, which I did. 2001 BMW 740i-100% synthetic is OE. No problem for 20K miles. Since then replaced valve cover gaskets twice, $700 each. At 70K miles slow, cosmetic, seepage at both main oil seals. Repair costs will approach the value of the car so I just put up with the occasional oil odors. I have a Pontiac Vibe that uses conventional oil. At 50K miles I have never had a repair, all seals are dry. 2014 CTD- 5K miles, no problems yet. Each time I installed synthetic I was assured that seals were designed for it. I've been driving since 1970 and have never had an engine repair from wear, the standard sales pitch justifying the additional synthetic cost. 100% synthetic oil is just a big, expensive scam and I will avoid it when possible.


This used to be an issue with pure ester based synthetic oils that caused rubber seals to contract. It is no longer an issue with PAO based synthetic oils that actually cause seals to expand. Even our modern Ester based synthetics include an additive package that conditions seals. 

I hate to say this but your post is full of pure misinformation. I replaced valve cover gaskets and manifold gaskets on all of my vehicles in the past using dino oil. Furthermore, after dozens of posts on this topic on my part, it would behoove you to acknowledge that modern synthetics (post 2006 for Mobil 1) are petroleum based, with the only significant differences from conventional oils being the removal of more contaminants and paraffin wax (to improve VI).

Our highest mileage members run synthetic oils and exceed 100k miles without issue. One of them is a personal friend and ran his Jetta TDI for over 500k miles without replacing a seal, all on synthetic oil. Furthermore, he sold his car with a camshaft that looked brand new, on an engine that was notorious for wearing down camshafts by 200k. 

Anecdotal evidence is a poor basis for giving technical advice.


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## Merc6 (Jun 8, 2013)

Using conventional oil in your Cruze will void the warranty.


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## Robby (Mar 1, 2013)

armobarak said:


> Well is that thickness harmful to the extent that i should replace that oil *now* and not wait for the scheduled usage (6000 miles)???


I can't imagine any harm by leaving it in.
Worst case is a check engine light if the cam phazers are slow to react but frankly, because synthetics flow so easily, I'd be surprised if that occured.

Take a look at your owners manual and see what optional grades are listed....these are written for the countries the vehicle may be operated in......just for your knowledge and ours if you want to share.

Rob


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## armobarak (Jun 25, 2014)

Robby said:


> I can't imagine any harm by leaving it in.
> Worst case is a check engine light if the cam phazers are slow to react but frankly, because synthetics flow so easily, I'd be surprised if that occured.
> 
> Take a look at your owners manual and see what optional grades are listed....these are written for the countries the vehicle may be operated in......just for your knowledge and ours if you want to share.
> ...


i checked the owner's manual and it recommends 5w30 or 5w40, which is why i was worried when they used the 5w50


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## XtremeRevolution (Jan 19, 2012)

armobarak said:


> i checked the owner's manual and it recommends 5w30 or 5w40, which is why i was worried when they used the 5w50


It will shear down to a 40 weight long before the oil life monitor is up. I wouldn't worry about it. 

Out of curiosity, what engine is this for? Do you have a digital copy of that owner's manual by any chance?


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## jalaner (Dec 28, 2013)

I checked the CTD manual and could not determine if the required oil is synthetic or a blend. I understand that using oil that does not meet minimum specifications in the maintenance schedule will void the warranty. That's why I continued using synthetic in the BMW despite the increased repair cost. My experience is that the risk outweighs the benefit when synthetic is not required. Perhaps I will be surprised, and finally, after 40 years of problems with synthetic in 3 different cars, the CTD seals will hold.


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## XtremeRevolution (Jan 19, 2012)

jalaner said:


> I checked the CTD manual and could not determine if the required oil is synthetic or a blend. I understand that using oil that does not meet minimum specifications in the maintenance schedule will void the warranty. That's why I continued using synthetic in the BMW despite the increased repair cost. My experience is that the risk outweighs the benefit when synthetic is not required. Perhaps I will be surprised, and finally, after 40 years of problems with synthetic in 3 different cars, the CTD seals will hold.


The dexos2 spec cannot be met by anything other than a "synthetic blend" oil. Whatever that means.


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## dhpnet (Mar 2, 2014)

If you ever have engine problems you run the risk that GM will refuse to fix it under warranty because you used oil that was not specified in the owners manual. Also, check the oil level on the dipstick. It's easy to let out a little oil if they put in too much.


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## armobarak (Jun 25, 2014)

XtremeRevolution said:


> It will shear down to a 40 weight long before the oil life monitor is up. I wouldn't worry about it.
> 
> Out of curiosity, what engine is this for? Do you have a digital copy of that owner's manual by any chance?



Unfortunately, the manual is in arabic not english, but i searched online and the attached pic describes the engine..


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## armobarak (Jun 25, 2014)

dhpnet said:


> If you ever have engine problems you run the risk that GM will refuse to fix it under warranty because you used oil that was not specified in the owners manual. Also, check the oil level on the dipstick. It's easy to let out a little oil if they put in too much.


Well it's the certified service center that used this oil!! But again here in Egypt the service centers are crap so what really worries me is the safety of the car not what GM would think!


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## sciphi (Aug 26, 2011)

I wouldn't worry about it this time. Next time use the recommended 5w-30 or 5w-40 oil. From what our biased media tells us, Cairo is a parking lot, so I might run 5w-40. Can't imagine how much 4 liters of 5w-40 would cost over there, since almost by definition that oil is a synthetic!


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## armobarak (Jun 25, 2014)

sciphi said:


> I wouldn't worry about it this time. Next time use the recommended 5w-30 or 5w-40 oil. From what our biased media tells us, Cairo is a parking lot, so I might run 5w-40. Can't imagine how much 4 liters of 5w-40 would cost over there, since almost by definition that oil is a synthetic!



lol when it comes to Cairo's traffic, your media ain't that biased, most roads here are full of traffic.

The 4 liters cost around 300 EGP = 42 USD


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## Yates (Aug 24, 2012)

My 2012 manual says 5w30 is preferred and 10w30 is acceptable under certain conditions. Does not mention other weights "being acceptable" so I for one wouldn't push it....warranty wise.


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## XtremeRevolution (Jan 19, 2012)

Yates said:


> My 2012 manual says 5w30 is preferred and 10w30 is acceptable under certain conditions. Does not mention other weights "being acceptable" so I for one wouldn't push it....warranty wise.


Use the 10W-30 whenever possible. Far better volatility.


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## Eddy Cruze (Jan 10, 2014)

I live in a hotter place than Egypt!

*Viscosity Grade​*SAE 5W-30 is the best viscositygrade for the vehicle. Do not useother viscosity grade oils such asSAE 10W-30, 10W-40, or 20W-50.Cold Temperature Operation: In anarea of extreme cold, where thetemperature falls below​​​​[FONT=Arial+22]−[/FONT]29°C([FONT=Arial+22]−[/FONT]20°F), an SAE 0W-20 oil may beused. An oil of this viscosity gradewill provide easier cold starting forthe engine at extremely lowtemperatures. When selecting an oil​of the appropriate viscosity grade,


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## Yates (Aug 24, 2012)

XtremeRevolution said:


> Use the 10W-30 whenever possible. Far better volatility.


I agree. I always used 10-30 in all my cars with no problems but I guess I fell victim to the 5-30 is best propaganda.


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## XtremeRevolution (Jan 19, 2012)

Yates said:


> I agree. I always used 10-30 in all my cars with no problems but I guess I fell victim to the 5-30 is best propaganda.


It really depends on what your coldest seasonal temperature is. Out here, we can get up to -15 degrees ambient. Cars don't really care what wind chill is. At that temperature, you benefit from a 5W-30 over a 10W-30 with better start protection on conventional and group 3 "synthetic" oils, which typically have a pour point of about -30 degrees F. 

With true Group 4/5 synthetics however, a 10W-30 will have a pour point of around -55F and the 5W-30 will be at around -60F. At that point, you're trading between a minor cold start fuel economy increase or a reduction in volatility. 

That said, most people don't use a group 4/5 synthetic, so unless you live south of the Mason Dixon line, you're better off with the 5W-30.


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