seeing as how synthetic oils are so superior to petroleum oils, then when purchasing a synthetic oil for my car do i have to be as concerned with the viscocity spread? i was contemplating using mobile 1 0w40 (not trying to get a debate on which weight of oil is better for my car) and was reading that with regular petroleum oils youve got to be concerned with viscocity spread due to the break down of the polymers. i understand that with the wider the viscosity spread the greater the use of polymers to achieve that viscosity spread. and over time that the polymers can break down and form deposits that can increase engine wear and decrease engine life. so with synthetics do i even need to concern myself with this spread or can i go with the 0-40 with no worries. also, with a 0 rated viscocity at cold temperature, does this offer enough protection to my motor at start up? ive taken a couple hours to read all about oils and these are some questions ive come up with that i havent found the answers to. (boring day!) thanks for any info.
dave

 

With synthetics it is often easy to create a larger spread like that because the better base oils they use often allow for better cold flow too, so they can naturally achieve the 0w status without the use of too much polymers, and still having the required hot viscosity to qualify as a 40wt oil.

That being said, Mobil 1 0w40 does show a tendancy to thin out in turbo cars, but seems to hold it's viscosity pretty well in the LT1 and other domestic V8s. I'd definitely recommend this viscosity over M1's 5w30, which is on the thin side of a 30wt and doesn't protect a hard driven LT1 nearly as well.

I still like the German Castrol 0w30 I'm using though. It's a very thick 30wt at operating temp, almost a 40wt, but it holds it's viscosity perfectly, it did not change one bit in my last oil analysis, and I have another oil analysis to report this week, I just changed the oil yesterday (with 6200 miles on it)

 

Patman,I have a question for you.You say the 0-30w is a good oil.What about in warm weather,what do you recommend?

 

where have you found these oils at? ive been to local dealerships and some chain stores (wal-mart, etc.) and a few of them carry a 0w20 but thats about it. ive yet to do an internet search, but i imagine thats what i'll have to end up doing to get these oils. unless someone knows where i can find these in a local place? thanks pat. i appreciate it.
dave

 

I ran the 0w30 Castrol last summer and got excellent oil analysis results. Because it's a thick 30wt oil it can handle the heat without a problem.

 

So far the German Castrol is only at Autozone in the US, and Walmart in Canada (as well as some Canadian Tire stores). As far as M1 0w40, I thought it was available in a lot of places in the US, including Autozone? It's not easy to find up here, the only place I know of in Toronto is a placed called Noco, which is more of a distributor than an actual store, so they've got limited hours of operation (only open until 3pm weekdays for instance)

 

The Autozones in my area have recently begun to stock the Castrol 0W30. Be sure to check the back to be sure it is the German made oil.

 

How about a good synthetic for here down in Florida? It is starting to really hot and those stop and go traffic days can really heat up my engine.

 

I would like to know the same thing. I'm in Florida too, and I'm switching to M1 10w30.

 

If you wish to stay with M1, their 0w40 (or the 5w40 formula which just came out) is the better choice.

 

Patman,
Am i right in assuming that the first part of the oil, the 0w or 5w or 10w is for cold starting, and the latter part is for once the car is warmed up? I'm not really set on M1, just looking for the best oil for the longevity of the car. If the german castrol formula is much better, then I rather switch to that. My options are pretty much open. My only concern is the 0w part since i'm in Miami florida and the coldest it gets here is like 60 for a day! I'd really appreciate the help. Thanks.

 

Yes, the 0w means it passes the cold weather cranking test better than a 5w or 10w oil. Don't worry about running a 0w oil in hot weather though, just think of the value at 100c, that's more important. Keep in mind that you want your oil to be as thin as possible when you start it up so that it flows better.

 

My Bro. just bought a Volks. GTI and it came from factory with German Castrol 0-w30.