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oprn Samba Member
Joined: November 13, 2016 Posts: 12632 Location: Western Canada
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Posted: Sun Jul 01, 2018 5:16 am Post subject: Re: The importance of choosing the correct oil weight. |
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Frodge wrote: |
oprn wrote: |
We have a Jetta TDI that uses 5W40 wt and has a tendency to leak a small puddle from the oil cooler seals when started cold at -20 or lower. Once it warms up it stops. |
I have 2 Tdis and use 5w40 in them. Are you saying that it leaks because of the 5w? |
No.
It is a common misconception that multi grade oils act exactly like the two weights published. A 5W40 oil is not as thin as a single weight 5w oil at low temps and is not as thick as a single weight 40W oil at high temps. It will be somewhere in between in both cases. It's not a perfect match but rather more of a compromise between the two is how I understand it.
In fact some days I wonder if it doesn't act the other way around but that is just an exaggeration!
What I am saying is that it would leak less in the winter if I switched to a 5W30 oil. |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50257
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Posted: Sun Jul 01, 2018 6:53 am Post subject: Re: The importance of choosing the correct oil weight. |
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oprn wrote: |
Frodge wrote: |
oprn wrote: |
We have a Jetta TDI that uses 5W40 wt and has a tendency to leak a small puddle from the oil cooler seals when started cold at -20 or lower. Once it warms up it stops. |
I have 2 Tdis and use 5w40 in them. Are you saying that it leaks because of the 5w? |
No.
It is a common misconception that multi grade oils act exactly like the two weights published. A 5W40 oil is not as thin as a single weight 5w oil at low temps and is not as thick as a single weight 40W oil at high temps. It will be somewhere in between in both cases. It's not a perfect match but rather more of a compromise between the two is how I understand it.
In fact some days I wonder if it doesn't act the other way around but that is just an exaggeration!
What I am saying is that it would leak less in the winter if I switched to a 5W30 oil. |
Well a straight 5wt oil isn't rated for cold starting as is a 5w** so I can't say if it is actually thicker or thinner at the 5w** cold cranking and cold pumping temperatures. I can however say that a **W40 oil is likely thicker than a straight 40wt oil at temperatures above 212°F as it has a higher viscosity index and thus should not thin out as much as the oil temperature goes up.
Last edited by Wildthings on Sun Jul 01, 2018 2:16 pm; edited 1 time in total |
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scottyrocks Samba Member
Joined: August 19, 2016 Posts: 2645 Location: Long Island, NY
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Posted: Sun Jul 01, 2018 11:32 am Post subject: Re: The importance of choosing the correct oil weight. |
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Frodge wrote: |
Thanks for the reply. I appreciate it. Will I do harm by having 10w40 in the summer? Asking because I changed it 2 weeks ago. |
No, actually, 10W-40 is preferable.
In multi-viscosity oils, the number before the W describes the flow in cold weather. The number after the W describes the thickness which is important in hotter weather.
The 10W part should cover our Bugs in NYC cold weather, while the 30 and 40 part will work in our summers.
Today and yesterday have been in the '90s. Imho, 10W-40 would be better for extended drives in this heat. My car has 10W-30 in it now. I will leave it in there unless the forecast for the rest of the summer will include a lot of days in the 90s. In that case I will change it out for 10W-40. _________________ “If you care for a thing long enough, it takes on a life of its own, doesn't it? Mending old things, preserving them, looking after them – on some level there's no rational grounds for it.”
– D. Tartt, 'The Goldfinch' |
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Frodge Samba Member
Joined: October 04, 2006 Posts: 1991 Location: Dump
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Posted: Sun Jul 01, 2018 5:09 pm Post subject: Re: The importance of choosing the correct oil weight. |
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I read this whole thread. Now I know why the moderators disallow this topic in the general forums. It reminds me of when I was a teenager. The police would let literally thousands of us drink our beers in the parking lots down at the beach off Father Capodanno Blvd, but would bust chops if we left there. They wanted all of us in one spot. Geez. I didn’t learn much from this at all. I’m going with use a 10w30 or 10w40 and change it often.
I do have one question though. If you take let’s say a10w30 oil and pour it out of a bottle, is it pouring like a 10w or a 30w? So basically, does the oil thicken as it gets hotter? |
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JaimeReyes Samba Member
Joined: May 30, 2018 Posts: 165 Location: San diego CA
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Posted: Thu Jul 05, 2018 2:57 pm Post subject: Re: The importance of choosing the correct oil weight. |
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so currently running some 10w-30 in the bug and everything seems fine. that was when the weather was max high 70s. it just started to get pretty hot. high 80s low 90s. should i switch over to a thicker oil? maybe a 10w-40 or 20w-50? |
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Steve Arndt Samba Member
Joined: August 01, 2005 Posts: 1777 Location: Boise, Idaho
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Posted: Thu Jul 05, 2018 3:02 pm Post subject: Re: The importance of choosing the correct oil weight. |
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JaimeReyes wrote: |
so currently running some 10w-30 in the bug and everything seems fine. that was when the weather was max high 70s. it just started to get pretty hot. high 80s low 90s. should i switch over to a thicker oil? maybe a 10w-40 or 20w-50? |
That depends on your oil pressures. _________________ Steve
Steve's 87 Syncro project |
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oprn Samba Member
Joined: November 13, 2016 Posts: 12632 Location: Western Canada
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Posted: Wed Jul 11, 2018 5:02 am Post subject: Re: The importance of choosing the correct oil weight. |
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If it is a TDI then I believe VW specifies 5w40 synthetic oil for all weather.
No I do not believe it is he "5" portion of the oil spec that caused the leak, more likely the "40" as I do not believe that a 5w40 oil really gets as thin as a straight 5wt oil at low temps. It just leans toward that value - sort of. |
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oibovveroi Samba Member
Joined: May 22, 2006 Posts: 744
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Posted: Wed Aug 29, 2018 7:57 pm Post subject: Re: The importance of choosing the correct oil weight. |
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1600DP stock fresh rebuild. Getting together all original tins and air flaps with thermostat. The builder suggested 20/50. I live in Southern California desert where temps will get down to 50-60 and as high as 120.
I’m leaning towards wanting to use 10/40 but would like to hear from you guys with more experience.
I’ve read through most pages but seems most responses were from people further north. |
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oprn Samba Member
Joined: November 13, 2016 Posts: 12632 Location: Western Canada
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Posted: Wed Aug 29, 2018 8:13 pm Post subject: Re: The importance of choosing the correct oil weight. |
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If it's indeed a stock built engine then VW's recommendations would be the way to go. |
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jpaull Samba Member
Joined: February 22, 2005 Posts: 3456 Location: Paradise, Ca
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Posted: Wed Aug 29, 2018 10:47 pm Post subject: Re: The importance of choosing the correct oil weight. |
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oibovveroi wrote: |
1600DP stock fresh rebuild. Getting together all original tins and air flaps with thermostat. The builder suggested 20/50. I live in Southern California desert where temps will get down to 50-60 and as high as 120.
I’m leaning towards wanting to use 10/40 but would like to hear from you guys with more experience.
I’ve read through most pages but seems most responses were from people further north. |
Your oil pressure guage will tell you if the 20-50 is too thick. Not anyone here on the internet. |
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fivelugshortaxle Samba Member
Joined: May 13, 2011 Posts: 4254 Location: Aumsville, Oregon
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Posted: Thu Aug 30, 2018 1:09 am Post subject: Re: The importance of choosing the correct oil weight. |
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Pick the correct weight oil according to the oil control springs and oil pump size combo you are using....also take into account what is plumbed in.....oil filter....oil cooler...I run the dreaded 30mm oil pump and 10/30 Amsoil Z Rod synthetic....runs cool oil temps and pressure is great
12 to 15 at idle and never goes about 50 when warm..cruising at 70mph and about 3,100 rpm oil pressure is right around 37 to 39 lbs. Oil temps stay between 18p and 195 on a 100 degree day and 3 hour cruise at 70. Oil pressure stays 12 to 15 psi at idle at emd of said cruise. Cool. _________________ Good things come to those who wait.
2332 with lots of goodies....
Rotating assembly balanced by Brothers VW
4340 84mm crank
AA 94mm p&c' s
Total seal 2nd ring, rest are Grants
5.5 h beams
Magnum straight cuts
Steve Long XR310 on a 106
CB 1.4 rockers
CB Magnaspark 2 distributor
NGK D7ea plugs
A1 lowdown 1 3/4 with single muffler
Dellorto 48's with 40 venturies
Kennedy Stage 2 with Daiken disc |
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Zundfolge1432 Samba Member
Joined: June 13, 2004 Posts: 12454
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Posted: Thu Aug 30, 2018 11:03 am Post subject: Re: The importance of choosing the correct oil weight. |
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Entered in error
Last edited by Zundfolge1432 on Thu Aug 30, 2018 3:02 pm; edited 1 time in total |
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FreeBug Samba Member
Joined: March 12, 2012 Posts: 4278 Location: deepest, darkest Switzerland
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Posted: Thu Aug 30, 2018 11:14 am Post subject: Re: The importance of choosing the correct oil weight. |
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Frodge wrote: |
I’m going with use a 10w30 or 10w40 and change it often.
I do have one question though. If you take let’s say a10w30 oil and pour it out of a bottle, is it pouring like a 10w or a 30w? So basically, does the oil thicken as it gets hotter? |
It doesn't get thicker, but it doesn't thin out as much as a pure SAE 10 would. Hot, it thins out to an SAE 30's viscosity.
Hot, most engine oils look like water. Cold, even SAE 5 behaves like oil.
not sure this is making sense |
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Splitdog Samba Split Personality
Joined: February 16, 2004 Posts: 4124 Location: Planet VW
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Posted: Thu Aug 30, 2018 12:43 pm Post subject: Re: The importance of choosing the correct oil weight. |
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I live in LA and I run 10/40 Brad Penn. _________________ CH³NO²
Z = z² + C
Der Blitzkrieg Kafers
#notacallooker |
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oibovveroi Samba Member
Joined: May 22, 2006 Posts: 744
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Posted: Thu Aug 30, 2018 2:59 pm Post subject: Re: The importance of choosing the correct oil weight. |
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Thank you for the info.
Unfortunately I don’t have an oil gauge, just the oil light.
I’m not sure of what kind of springs etc. was told a HD oil pump.
I’m not very knowledgeable about those sort of things, I bought the engine from a reputable builder in the area who has excellent feedback. I asked for a completely stock 1600 and assumed that’s what I got, but I digress.
I’m going to go with either brad penn, or maybe Lucas classic car oil.
Both have 10/40 and 20/50. But the brad penn also have 30w and 40w.
It seems I’ve read 20/50 tends to give trouble, but it gets as hot as the lake of fire here. Perhaps I’m over thinking.
Anyways the brad penn is conventional synthetic mix. It’s ok to run synthetic on a fresh rebuild? Should I use brad penn break in oil first? |
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Splitdog Samba Split Personality
Joined: February 16, 2004 Posts: 4124 Location: Planet VW
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Posted: Thu Aug 30, 2018 3:12 pm Post subject: Re: The importance of choosing the correct oil weight. |
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If it hasn't been started, I would definitely run BP break in oil. Then 10/40 after. _________________ CH³NO²
Z = z² + C
Der Blitzkrieg Kafers
#notacallooker |
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Ghia73Girl72 Samba Member
Joined: February 13, 2006 Posts: 31 Location: Clarkdale AZ
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Posted: Thu Sep 13, 2018 12:00 pm Post subject: Re: The importance of choosing the correct oil weight. |
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I live in the Arizona high desert and was told by an esteemed local mechanic when we bought our Karmann Ghia (1973 model with 1990s-installed 1835cc engine) 20 years ago to always use straight weight oil: 40W in the heat of summer (days above 100 degrees, so basically May-September) and 30W the rest of the year. And that's what we've always done. Changed every 2,000-2,500 miles without fail. Deep sump and Bosch screw-on filter.
I see now that this perhaps might be a cause of various drips and "marking our spot" in various parking lots. However, at this point, even after rolling the odometer once, I don't think I'd change to another oil plan. |
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[email protected] Samba Member
Joined: August 03, 2002 Posts: 12785 Location: Salt Lake City, Utah
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Posted: Thu Sep 13, 2018 4:59 pm Post subject: Re: The importance of choosing the correct oil weight. |
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Not to be captain obvious here, but oil is SUPPOSED to be thin, since it has a limited time to squeeze into .002 gaps. It's laughable that people think that 40 or 50W oils are going to be able to do this.
Get a gauge. If not electrical (permanent) at LEAST put a mechanical one on in the driveway after the engine is hot, and rev it up and check pressures at idle and 3500.
If you are too lazy for that, nobody can help you. _________________ It's just advice, do whatever you want with it!
Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net
"Like" our Facebook page at
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and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net |
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oprn Samba Member
Joined: November 13, 2016 Posts: 12632 Location: Western Canada
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Posted: Thu Sep 13, 2018 7:34 pm Post subject: Re: The importance of choosing the correct oil weight. |
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It likely take 15 minutes for that thick tar to make it's way up the pushrod tubes on start up on a cool day. Then guys wonder why galling shows up on the rocker arm shafts and the valve guides wear out! |
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vwracerdave Samba Member
Joined: November 11, 2004 Posts: 15280 Location: Deep in the 405
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Posted: Thu Sep 13, 2018 8:43 pm Post subject: Re: The importance of choosing the correct oil weight. |
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I've run 10W-30 oil in 100* heat on several engines over 2000cc without overheating. _________________ 2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63
Watch my racing video's http://www.youtube.com/user/okvwracer/videos |
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