20w50 is far too thick, you'll end up with higher oil temps due to the engine working too hard to pump that thick oil. The clearances in these engines are not designed for such thick oil. And a 10w40 synthetic will offer more than enough protection even on the hottest days of summer. You'll just see more engine wear with a thicker oil, it won't flow as well and on cold starts (even in the summer) the thicker oil won't protect as well as a faster flowing oil like 5w30, 10w30, 10w40 would.

 

Castrol GTX

 

I agree that 20w50 is far too thick. But I'm from Fort Lauderdale Florida (near Miami) and there's no such thing as a cold start in summer. Let that thing bake in the sun all day and you're probably turning the engine over at about 130+ degrees. Dude, you're from Ontario.

 

When I say cold start, I don't mean the outside temperature is cold, but simply that the engine is cold. Even when it's 100F outside, and you start your car after it's been sitting for a long time, the oil is super thick, and when it's a 20w50, it's even thicker. So even under those conditions, a 5w30, 10w30 or 10w40 oil would flow much faster.

It's not as cold in Ontario as you think. Most overnight temps here in the summer have been no lower than 70F, and during the day it's gotten to 90-95F a few times too.

 

Patman, I went to look for the Castrol SLX, but I haven't been able to find it. Where do you get that at? I haven't looked for it at Autozone yet, do they carry it?

 

I believe he has a (Germany) following that listing.

 

He has also said in the past it is available in the States, it is just harder to find.

 

i have over 150,000 mi on my car and i have not had 1 problem with my engine. everyone here including mechanics say to use 20w50 on v8 engines. do more research my car runs like its new.
just my advise with my experience.

 

Just curious, but whats so special about that oil?

 

If you have read any of Patmans other post you would know, he has done a lot of research on oil. I suggest you read up on

Bobistheoilguy

 

Castrol Formula SLX 0w30 is sold in North America under the Syntec name, but you have to make sure it says Made in Germany on the back, it's the new label stuff with the red 0w30 on the front NOT the yellow 0w30 with the snowflake. This oil is better because it's formulated with a much better base oil, which allows it to flow extremely well in the cold, but yet it's got a viscosity at 40c comparable to a typical 10w30 oil, so it's not super thin in the summer. And it's hot viscosity at 100c, is 12.1, so it's a very thick 30wt oil, almost a 40wt, so it protects better. I just got back an oil analysis on it in my sister's car, and the viscosity stayed very close to original (final viscosity after 5500 miles was 11.5) and it still had a very strong TBN left (acid neutralizing ability) This oil passes some very stringent European tests, and is designed for their much longer drain intervals.

So far it's only sold at Autozone in the US, or Walmart in Canada. Unlike the rest of the Syntec lineup, it is a true full synthetic oil.

Now back to the 20w50 issue, I know a lot of you will ask why this oil still exists if it's not good to use in most cars. Honestly, it shouldn't really be sold to average people, it's more for older engines and race cars. A lot of you are probably thinking, well, I have a modified car, so don't I qualify as being a "race car"? Well not really. A pure race engine would have much looser clearances, and because of that, and the way most of them are tuned to run rich, they'll get more fuel dilution into their oil. So they need the thicker oils since as more fuel gets into it, the thinner the oil will get. Also, with a pure race situation, they might see old temps of 250F and higher for long periods, so that thicker oil is needed in that case too. For a production engine, even one that's modified with cam/heads/supercharger, etc, you can get all the protection you need out of a very good synthetic oil that is 10w40. There are many good oils out there that are 0w30, 5w30, 10w30, 0w40, 5w40, 10w40. The ones I prefer are the ones that are on the thicker end of the 30wt scale, to the lower end of the 40wt scale (so their 100c viscosity is in a range of between 11.5cst to 13.5cst approximately)