I find these 2 brand in store~

Mobile 1 : 5W30, 10W30, 15W50
Castol : 5W30, 10W30, 5W50

average temperature -15C
lowest temperature -30C
which grade should i go for

and can someone told me what is the number following W means???

 

Castrol synthetic oil is mostly very high grade fossil oil. Mobil 1 is the good stuff. I use 15w50 here in sunny Florida all year round.

 

MOBIL 1 15W50

 

Mobil 1 15W30 for me and it works like a charm!! I will be using 15W50 once I get my new turbos.

Zach

 

lubrication engineers. break down temp is much higher than either.

 

isn;t castol fully synthetic too????

 

what is the last number mean???
isn't Castol Syntec full synthetic oil too???

 

I've been very happy with Royal Purple 10W30. I think their web site has a dealer locator...I get mine from Speed and Truck World here in Fort Lauderdale. I mail ordered some once, maybe Jegs? I don't remember, it ended up being about the same price to buy it locally.

jds

 

W stands for "******" factor.

 

Although a little bit more expensive than Mobil 1, I am very happy with Royal Purple. I've run Red Line, Mobil 1, Amsoil, and Royal Purple. Of the four, the Royal Purple has my vote with Red Line right behind it.

 

The ratings are actually 10W-30, etc. The W after the 10 means that it flows like 10 weight oil at freezing. The 30 means it flows like 30 weight oil at a higher temp (I don't remember the exact temp). Oils that have two numbers like this are "multi-viscosity" oils since they change their weight across the temperature range. They thin at cooler temps so they flow better on cold starts to reduce cold-start wear. That doesn't mean its actually thinner at freezing than it is when hot, but rather that it just flows like 10 weight oil flows at freezing, which is almost certainly thicker than 30 weight oil at the higher temp.

Oil weights are viscosity specifications, and they aren't exact. Mobil 1, for instance, tends to be thinner than other oils of the same nominal viscocity specification (like 10W-30), but of course both oils meet the spec. The spec is the time required to flow a specific amount through an orifice of a specific size at some temp. As an example, oil that takes 30 to 45 seconds on some test might be one weight, and oils that take 45 to 60 seconds might be a different weight. That sets up a situation where you could have one oil that takes 31 seconds and another oil that takes 43 seconds meet the same weight specification, even though the one that took 31 seconds is thinner.

Or at least that is my understanding of the ratings. I read that all some time ago, and the examples are intended to be illustrative rather than specifically accurate. I won't be offended if someone cares to post corrections or more accurate examples.

-Max

 

Couldn't have said it better myself Max!
And as for the question of Castrol being fully synthetic, NO. There are 2 manufacturers in the World that have the technology to make a fully synthetic oil.....
Mobil One
AmSoil
All others are a synthetic blended formula. If it contains some synthetic elastomers or polymers it can be technically graded as synthetic. Most applications this won't make a bean hole of difference but in racing app's you'd better be sure your willing to sacrifice that motor or lubricated part to save a couple bucks up front for a lower quality oil.
Art

 

okok
thx rts3gen
i will stick with mobile 1 then~
hehe

 

Just changed oil today to mobil 1 0w-30. i'll keep you posted if anything breaks