Leander311

iTrader: (2)

First number is cold weight, so the 0w30 theoretically pumps better at lower temperatures, providing better cold-start protection.

Increased spread between cold-hot viscosity numbers usually require more VII (viscosity index improvers), which are the most-prone oil components to HTHS (hi-temp, hi-shear) breakdown. That's to say the oil may not stay in its viscosity range as long as a 5W-30 would.

Only a UOA will tell you for sure. In my TX climate, I'll be sticking to Penn Plat 5W-30, or possibly GC (German Castrol, a relatively heavy 0W-30. I've got a stash of both from my totaled Mazdaspeed3. We'll see what the UOA on PP looks like, then may try GC next summer since it will be fall/winter before the end of my current OCI.

brociouz

iTrader: (65)

The first number is the same in 0w20 vs. 0w30, so why would one provide better cold-start protection than the other?

Thanks for the info. I didn't know about the problems associated with a high spread. Gah, so hard to decide on what oil to get. 0w20, 0w30, 5w20, 5w30? I've even seen 0w50 (Eneos). (I know it'll probably make no difference assuming I change my oil at appropriate intervals, but OCD strikes again.)

Leander311

iTrader: (2)

Sorry, your question appeared to be about 0W-30 vs. 5W-30. Cold-start protection of 0w20 vs. 0W-30 should be negligible, but again these will have different VII values, so ultimately the 0W-20 might be a bit more shear-stable, which is to say its published viscosities are more likely to hold up longer.

I know what you mean about OCD. I was a member of SAE for a while and designed race cars a bit in college. I'm still a professional mechanical engineer but don't get to play with cars nearly as much as I once did or would like to. I spent far more time reading up on oil than I ought to have, but again the end results were great; my UOA's on my MS3 were incredible. Yet after all that effort, my car was lost, the life lesson being you can prepare until you are blue in the face for one thing, but then another thing comes along and renders all your preparation moot.

As they say, opinions on oil are like... well, you know, and there are a lot of uninformed/misinformed folks out there who have strong opinions despite their ignorance.

IMHO, reading what folks have to say about oil is pointless unless they also offer some independent, empirical data to back up their beliefs. Until then, they're just selling religion. That's why I'm trying hard to bite my tongue until I have a lab report or two to offer. All I can say now is I'm really excited about how much easier even one of Toyota's "hottest" engines is on oil than MS3 was on its oil.

brociouz

iTrader: (65)

Oops, you read my question right, I just lost my train of thought (haven't had my coffee yet, and 3 hours of sleep isn't helping).

So now I'm thinking I should go with either 0w20 or 5w30... I will be drag racing my car later this year so maybe 5w30 for the operating temp protection?

Cool, during my first couple of years in college I was in ASME and a team leader on my school's Solar Racing Team... and now I work in finance.

Looking forward to your results.

embolism

never played around with 0W's just have always run 5W 30 but I just went from Mobil 1 synthetic to the BMW synthetic racing oil and my highway readings for mileage went down to 8.7 L / 100 km for the first time ever. I was mainly driving at 120 km/hr too which is not the optimal speed for mileage...

Best my wife ever did for highway driving down to Boston was 9.8 L / 100 km.

wow