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Synthetic Oil! 0-40, 5-40, 10-40

2008 Jetta S 2.5 , VW 502 oil specs are met by Moble1 synth 0-40W, 5-40W, 10-40W.

Back in the day of one weight oil, the standard philosophy was the hotter the driving conditions the heavier the oil used. End of problem.

My question (which I’ve had since synth came out) is now with these multi viscosities does the same philosophy apply? Do I use 10-40W because I live and drive in Florida? or is 0-40W still OK in Florida?

It’s the greatest mystery of the New Baloneyum. I haven’t read the latest Nicene Creed of oil so I wouldn’t even try to answer the question. Kind of like the people we elected to counter the president we also elected. Why do we do that?

Ha! Like it,
Tnx for the comment.

When looking at multi-viscosity oils ie: 5W-30, the first number, 5W is the winter weight of the oil. This is the viscosity of the oil when the engine is cold so that the engine is provided with lubrication is soon as possible when it’s started. Once the engine reaches operating temperature the oil has the viscosity of a 30 weight oil.

So you can use a 0W-40 oil if you want. It just means the oil will flow faster on a cold start than a 10W-40 oil. But both will have the viscosty of a 40 weight oil once the engine reaches operating temperature.


OK, good info. But, It is rarely cold here in FL. Would my engine be better protected with the 10-40W as apposed to the 0-40W ?

I would have purchased 10-40W based on this/ my understanding but typically difficult to find the 5 or 10-40W. So I purchase what I can at the time I have available to change. Also, when on sale at Auto Parts, with filter.

... Moble1 synth 0-40W, 5-40W, 10-40W

The 10W-40 grade is intended for those who live in tropical or semi-tropical climates. The other grades are also acceptable for Florida residents.

Does you owners manual have anything to say about this? Some have a diagram with a temperature range and the different viscosity recommended.

Mobil 1 10-40 is not VW 502 approved .

Here’s a list of oils that meet that spec .

Genex, your list is for the GTI, which has that nifty turbo. The OP is driving the tamer Jetta.

Google “Viscosity Index Improver” and how they work to understand what is going on here…

The VI’s reading is interesting. Yes, part of my dilemma is that I do not have an owner’s manual so I must sift through information listed in various sources

The list of oils that meet vw502/505, this is also interesting that the 10-40W was not listed here, I’m sure I found it listed elsewhere.

But this is my concern, is that the 0-40W is not appropriate even though listed in many sources. 0W just seems like “zero protection”

The 0 winter weight means the oil flows quickly to major engine components under friction to protect them. Friction creates heat. So as soon as the 0 weight oil see’s this heat from friction it converts to a 40 weight oil.


I recommend starting by checking to see what VW recommends for your model/engine.

The VW spec for this car is VW 502 .
O-40 does not mean no protection - it is a label that means that the oil meets the SAE cold flow tests for a 0 rated oil .
Why is it 0 - because when the specs were first set up no one conceived of a motor oil at that viscosity . Originally a 20 rated oil was considered thin .

0 does not mean no viscosity .

BTW I use 0-40 in my VW and have for more than 100,000 miles - the car uses one quart every 2500 miles - does that sound like no protection ?

The 0 in 0-40W is not an indication of no protection. In Florida and just about everywhere else in the US either 0W or 5W multi-weight oils are fine. The 0W means a thinner base oil than the 5W or 10W oils. The thinner oils will flow better and quicker in low to extremely low temperatures. Additives and other tricks are used to keep the oils from thinning out as the motor temp rises, hence the 20W, 30W, and 40W indicates how thick the oil is at operating temperatures which now can be 210 degrees F.

The 0W oil might burn off a bit faster, so if you check your oil levels you might find you need to add a bit more oil between changes. That is about the only difference. In Florida you could likely use any of the oil options you listed with no damage to your car at all.

Just use the 5w-40 Mobil 1 and stop worrying.

Thanks for all the comments! I do appreciate it! The reason I went with the O-40W was because of the sale and 5-40W was not available. I guess I could have waited until it came in , but you know time and schedules , I realize the 0-40W , 0 does not mean zero protection, but it has got to be water thin, even with additives I’m still nervous.

I just wanted to hear, Its OK for someone who actually uses it, knows the temperature ratings, It really is hot here in FL!

Thanks again, Does anyone have a good site on this car/engine/ oil ? The problem is VW does not list its motor manual stuff on line that I can find?