# Is it a myth to change oil according to season?



## juni returns (Apr 4, 2008)

I talked to a mechanic friend of mine the other day about motor oil. My jetta has about 192,000+ miles on it on the original 12V VR6 motor. This past spring 2008 till now, I upped the weight from the normal 5W40 that was being used to Mobil 1 10W40 because one of my other friends said that it would be better to keep the internals lubricated because my motor has a lot of mileage on it. 
Is it a myth that when the weather gets colder, I should move back down to 5W40 motor oil, and then when it gets warmer, move back up to 10W40?
Or since i have upped the weight to 10W40, should i Just keep it that way until the car dies?


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## franz131 (Apr 13, 2008)

*Re: Is it a myth to change oil according to season? (juni returns)*

The myth is the belief that there is automatically a difference in the operating viscosity between 5w40 and 10w40. The only difference in the specification is at low termperatures, where the 10w is thicker = slower flow.
That said, it is entirely possible that the 10w40 you use is thicker at operating temperature than your choice of 5w40, but you'd have to compare data sheets or UOA to know that.
A VW spec 5w40 (or 5w30 for that matter) is required to have an operating viscosty on the high end of the Xw40 range. The faster flow at low temps is the bonus you get from high tech oil.
VW spec trumps API vis ratings.


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## AZV6 (May 3, 2006)

*Re: Is it a myth to change oil according to season? (juni returns)*

No need to. 
I would use 5W-40 all year. 10W-40 does not run well in this engine, especially Mobil 1, which is not approved either. Use 0W-40 Mobil 1 only.
Stick with 5W-40 no need to go higher.
I rather have a low winter number all year for quicker lubrication at start up when it needs it the most. Higher winter number of course means it is thicker and takes longer to lubricate at start up. Hot or cold I would want it faster, 40 weight is the same, thats a good weight. Make sure it is 100% synthetic oil so it does not shear down to a 30 weight.
Use Pentosin, Motul, Castrol Syntec 0W-30 or something like that. All European oils which IMO are much better than US made oils.
Real 100% synthetic.
Will protect your engine under most climates. 
Simply put 10W-40 is not a good choice, use 5W-40 approved oil all year.


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## bcze1 (Feb 6, 2007)

*Re: Is it a myth to change oil according to season? (franz131)*


_Quote, originally posted by *franz131* »_The myth is the belief that there is automatically a difference in the operating viscosity between 5w40 and 10w40. 

I don't think the "myth" has anything to do with operating visc, especially since the operating visc is the same. Its based on start up viscosity and wear. I think its more important to stay with an oil approved for your motor that to focus on seasonal variations, but there is a real difference between say a 0w30 and 10w30 engine at below freezing temps. Actually starting the vehicle is more difficult with the 10w not to mention the potential for increased wear during that short but important time.


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## tjl (Mar 24, 2001)

*Re: Is it a myth to change oil according to season? (juni returns)*

It was not a myth then most oils were conventional oils, so that "very wide" grades like 5W-40 were not available, and "wide" grades like 10W-40 tended to not stay in grade very long (e.g. 10W-40 becomes like 10W-30 after a few thousand miles). Also, single grade oils (like just 30, or 10W) were more common.
But things have changed:
* Many engines can now run on 30, rather than 40 or 50, at operating temperature. Some newer engines can run on 20 at operating temperature.
* Engines and cooling systems are better, so engine operating temperature is now better regulated and less dependent on ambient air temperature.
* Synthetic oil has become more common, allowing for "very wide" grades like 5W-40 or 0W-40.
* Conventional oil has improved, so that "wide" grades like 5W-30 can stay in grade for a full oil change interval.
So now it is common for manufacturers to recommend a single grade (often 5W-30 or 5W-40, but now sometimes 5W-20) year round. Seasonal variation is unlikely to be necessary unless you live where temperatures reach arctic levels (in which case changing from 5W-whatever to 0W-whatever (e.g. 5W-30 to 0W-30) may help in cold start conditions.
Changing from 5W-40 to 10W-40 just makes the oil more viscous during cold start conditions, which may make it slightly harder to start and cost a bit in fuel economy until the engine is warm. Unless oil analysis indicates that 5W-40 is not staying in grade the full oil change interval, it is not likely that going to 10W-40 (especially if you go to conventional oil) helps anything.


_Modified by tjl at 8:51 PM 12-11-2008_


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## juni returns (Apr 4, 2008)

*Re: Is it a myth to change oil according to season? (tjl)*

well what about the fact that i have 192,000 miles on my car and i've been using 10W40 for at least 10 months now... should i just convert back to 5w40 and leave it that way till my car dies? I thought that 10W40, being more viscous, would be better for my internals because my car has a lot of mileage?


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## AZV6 (May 3, 2006)

*Re: Is it a myth to change oil according to season? (juni returns)*

Naah. Go back. I would want the faster lubrication regardless of weather and miles. In fact I would prefer a 5W-40 on a higher mileage motor. The tolerances are pretty close in these cars anyway, even with some miles. 192K is a lot but not too bad, if taken car of I can see it going another 100K or more easy.
Now that being said if you feel like using a 10W-40 go ahead, just use synthetic.
Jason


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## juni returns (Apr 4, 2008)

*Re: Is it a myth to change oil according to season? (AZV6)*


_Quote, originally posted by *AZV6* »_Naah. Go back. I would want the faster lubrication regardless of weather and miles. In fact I would prefer a 5W-40 on a higher mileage motor. The tolerances are pretty close in these cars anyway, even with some miles. 192K is a lot but not too bad, if taken car of I can see it going another 100K or more easy.
Now that being said if you feel like using a 10W-40 go ahead, just use synthetic.
Jason

So you think I should switch back to 5W40 even though i've been using 10W40 for 10 months now? Would that affect my car in any way is what i'm asking? If i go to a lower weight oil even though i've been using a higher weight, would the internals not be as lubricated and will the motor end up not lasting as long?


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## juni returns (Apr 4, 2008)

*Re: Is it a myth to change oil according to season? (juni returns)*

anyone else have any input?


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## juni returns (Apr 4, 2008)

*Re: Is it a myth to change oil according to season? (juni returns)*

oh i dont know if i mentioned this but i'm using Mobil 1 10W40 High Mileage FULL SYNTHETIC just to make that clear... last winter, i switched down to Amsoil 5W40 full synthetic just for cold starts and then the following spring, went back to the mobil 1 high mileage full synthetic. 
*So i was just asking again if switching between two full synthetic formulas, is it ok for me to go from 10W40 full synthetic in spring thru fall to 5W40 full synthetic in winter and back to the 10W40W full synthetic next spring a bad thing for my engine with 192,000 miles on it? is it bad for internals?*


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## franz131 (Apr 13, 2008)

*Re: Is it a myth to change oil according to season? (juni returns)*

Juni, you're question has been answered repeatedly, I'll recap.
Your car has a lot of miles on it.
You switched to a 10w40 on the advise of a friend.
Respondents to this thread have expressed the following:
Your 10w40 is likely not any thicker than your VW spec 5w40
Your 10w40 flows slower at startup.
A VW spec 5w40 does everything you need
Some actual numbers:
Mobil 1 10w40 vs. Brand X 5w40 (VW 502)
Vis @ 40c 103 vs 86
Vis @ 100c 14.7 vs 14.3
Flash point 227c vs 230c 
Use a VW spec 5w40 all year round, your choice of 10w40 is not doing what you want it to.


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## tjl (Mar 24, 2001)

*Re: Is it a myth to change oil according to season? (juni returns)*


_Quote, originally posted by *juni returns* »_well what about the fact that i have 192,000 miles on my car and i've been using 10W40 for at least 10 months now... should i just convert back to 5w40 and leave it that way till my car dies? I thought that 10W40, being more viscous, would be better for my internals because my car has a lot of mileage?

10W-40 is thicker than 5W-40 at cold start. Note that 10W and 5W are both thicker at cold start than 40 at operating temperature is.
Stick with VW 502.00 rated oil (which mostly comes in 5W-40, sometimes 5W-30, 0W-40, or 0W-30) as recommended by VW in an update from around 2004.


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## juni returns (Apr 4, 2008)

*Re: Is it a myth to change oil according to season? (juni returns)*

Thanks for the advice everyone, i'll switch to a vw approved 502.00 oil. Now another question... 
*Does anyone think that by using a non-vw approved oil, like that mobil 1 10W40 full synthetic i was using for 10 months, is that enough of a time to do damage to internals in an engine that has the high mileage already?*


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## skip57 (Nov 7, 2008)

*Re: Is it a myth to change oil according to season? (franz131)*

THE ONLY THING THAT WAS NOT SAID OR ASKED WAS . DO YOU START THE CAR AND DO SHORT RUNS, CUT IT OFF BEFORE IT IS AT RUNNING TEMP. IF SO YOU NEED THE HIGHER WEIGHT FOR THE START UP. THE OTHER SIDE IS MPG, 10 WEIGHT WILL LOWER YOUR MPG (IE. CAF & EPA REG.S =5W) AMBIENT TEMPERATURE AND OIL USE ARE IN THE OWNERS MANUAL. I use 10 w 40 yr. round


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## franz131 (Apr 13, 2008)

*Re: Is it a myth to change oil according to season? (juni returns)*


_Quote, originally posted by *juni returns* »_*Does anyone think that by using a non-vw approved oil, like that mobil 1 10W40 full synthetic i was using for 10 months, is that enough of a time to do damage to internals in an engine that has the high mileage already?* 

The specific areas where a 502 oil differs from an API oil is in the viscosity requirements, oxidization resistance and sludge control. 
You aren't really in any danger of mechanical damage, just run a quick engine flush at your next oil change.


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## AZV6 (May 3, 2006)

*Re: Is it a myth to change oil according to season? (juni returns)*

Mobil 10W-40 runs very very sluggish in the VR6 engine. I would switch to the approved 0W-40 Mobil 1.
I myself use 5W-40 Pentosin. Runs a hell of a lot better than the Mobil 1.
10 months is nothing for the motor. I would not run 10W-40 IMO, approved 5W-40 or 0W-40 or 5W-30 is fine. Using a good synthetic like ones made in Germany or Europe are the best way to go if you have a source for them. Otherwise Mobil 1 0W-40 is the only approved oil in the mobil range. 
Short or long runs is not a big concern IMO, shorter runs change a bit sooner and use 0W-5W-40/30. Dump the 10W.
Jason


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## juni returns (Apr 4, 2008)

*Re: Is it a myth to change oil according to season? (AZV6)*


_Quote, originally posted by *AZV6* »_Mobil 10W-40 runs very very sluggish in the VR6 engine. I would switch to the approved 0W-40 Mobil 1.
I myself use 5W-40 Pentosin. Runs a hell of a lot better than the Mobil 1.
10 months is nothing for the motor. I would not run 10W-40 IMO, approved 5W-40 or 0W-40 or 5W-30 is fine. Using a good synthetic like ones made in Germany or Europe are the best way to go if you have a source for them. Otherwise Mobil 1 0W-40 is the only approved oil in the mobil range. 
Short or long runs is not a big concern IMO, shorter runs change a bit sooner and use 0W-5W-40/30. Dump the 10W.
Jason

I'm actually going to dump the 10W40 and I found at autozone that Castrol Full Synthetic 5W40 is specifically made for BMW, Mercedes, AND VW having the VW502.00 spec rating on it.. so if i cant find mobil 1 0W40 european formula at walmart, i'll just get myself 6 quarts of the castrol 5W40 and run that till my car dies
*thanks everyone for your help with my dilemna as it has proved useful to all that helped me to understand my vdub better! * http://****************.com/smile/emthup.gif


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