0W-40 pros & cons...

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If your speced for a CAFE 0/20 and concerned for drag friction vs. wear just short fill it with 0/40 like 1/8" lower than you would otherwise.
...double protection with even less friction drag.
 
Some of the newer engines are specifically designed for xw20 oil verses engines that were designed for multiple grades that can use xw20 and get by with it.
If the engine is designed for it there is no benefit in going with heavier weight oil, in fact with the clearances and surface finish on the crank and dual stage oil pumps it may be detrimental.
 
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40 weight is becoming a dead issue. Take a look at GM. 0-20, 5-20, 5-30. Period.

Gas mileage requirements and a need for thinner oil to keep the AFM system operable are the main reasons. The Doxos designation is required to keep those fancy lifters in good shape.

SF
 
OK, I'll bite...how does underfilling a bit lower the friction drag?
I would imagine any reasonable answer would also imply a loss of protection...
 
Originally Posted By: Virtus_Probi
OK, I'll bite...how does underfilling a bit lower the friction drag?
I would imagine any reasonable answer would also imply a loss of protection...
ya what the heck?
 
I honestly don't believe this "modern engines are specifically designed for xw20 only" thing. Sure modern engines run well on 20 grades, and they are well establish oils that work well and protect well, they are also certainly encouraged by the manufacturer as they ccontribute positively to fuel economy - maybe only a little bit, but it all adds up.

If you look at engine clearances they are typically measured in 10's of microns, while if you look at operational oil film thicknesses they are typically measured in single microns (Shannow has some good tables here). Any reasonable oil grade should operate fine in any reasonable mass produced engine. As long as it starts OK or it's not being raced.

Also look at the effects of temperature
M1 0W40 FS
KV40 = 70.8 cSt
KV100 = 12.9 cSt

M1 0W20 AFE
KV40 = 44.8 cSt
KV100 = 8.7 cSt

Right now I am in the middle of an hot Australian summer while most of you are in the middle of a cold North American winter. It's not unusual for me to "cold" start my car at 40C and quickly go up from there, here overheating cars, of which I've seen a few recently, are the big issue. But in NA you could be starting your car at -30C and maybe then short tripping it to work, with the oil never fully heating up.

Given the above situation, with the same cars, me running 0W40 in Australia and you running a 0W20 in NA, it's quite possible that for most of the drive I'm running the lower viscosity oil (as in operational viscosity). It's easy for a cold 20 grade to be a lot thicker than a hot 40 grade.

So if a modern engine isn't designed to run well on a 40 grade at full operational temperature, then how does it run on a 20 grads at below 0F (-20 C) ?
 
OK I am officially a 0w20 convert...I think... BUT 0w40 does have a lot of benefits. This is just from personal experience with my vehicles, your results may vary.
Pros:
- Much easier starting than any 5w30. I started to notice the difference from 40°F and below.
- Little to no "metal rattle" at high RPMS, compared to 0w20, 0w30, 5w30. It is more of a metal cricket sound than a rattle, but 0w40 heals it. No, it is not a mechanical problem, just the nature of the engines I serviced.
- Same type of rattle/tick never shows up after excessive idling on 0w40. It always becomes more audible after excessive idling with 0w20, 0w30, 5w30.
- Out of 0w40s that I have tried - PENNZOIL 0w40 SRT actually improves my MPG by a hair across the range. Improved the MPG in 2006 Toyota Highlander Hybrid by 3mpg.


Cons:
- Castrol 0w40, Mobil1 0w40, and PENNZOIL Euro 0w40 give a slight MPG hit. Very little, not significant, maybe 1-2mpg at most across the board. PENNZOIL 0W40 SRT DOES NOT have that issue.

No other Cons from my experience in my daily drivers. Results could be different in more demanding applications. Just sharing my real world experience.
 
I don’t understand the underfilling having any relevance.
The viscosity difference is negligible.It really doesn’t make a big difference. Low power engines (less this 200hp)May have a difference in performance while cold.
 
Originally Posted By: SR5
It's easy for a cold 20 grade to be a lot thicker than a hot 40 grade.

So if a modern engine isn't designed to run well on a 40 grade at full operational temperature, then how does it run on a 20 grads at below 0F (-20 C) ?



EXACTLY! Funny how so many people refuse to realize that simple fact.

P.S. I really Crack up when I hear or read some people say that they don't want to use w40 because it will clog up the oil passages in the engine.
 
Designed specifically for thinner oils...

OK, Honda admit that they are making bearings bigger (length and diameter), while reducing oil clearances. This is the behaviour to increase minimum oil film thickness with thinner oils...aka they have reached the point where they can't go thinner on bearings.

Why are they doing this ?

Primarily to reduce the still comparatively massive piston/skirt frictional losses, by reducing viscosity.

This will decrease skirt drag, while increasing bearing drag, so there's an optimisation taking place.

So YES, Honda are designing engines for thinner oils.

But that's not an argument that these engines must exclusively use them. Per SR5, can't ever cold start them if 12Cst is going to damage an 8cst engine.
 
Sounds like adding a bit less of 0w40 in his thoughts will create less internal drag per se. I would go half 0w20 and half 0w40 if its really cold like Wisconsin. Many Hondas have low tension rings so too thick can cause ring and vtec issues.
 
if sump capacity is kept reasonable but lower it must offset drag...not that I let drag bother me but for someone who does there you have it.

don't fill that badboy to the rim and your golden.
 
Can be a cool strategy:
1. Put M1 0w40 in your engine spec'ed for 0w20 or 0w30 on May 1.
2. Commit to a year (up to 15k miles) on the oil change interval.
3. By December, the oil will have likely sheared down to a 20 or a 30 weight, for winter.
Loss of the VII chemicals 6 months into the run wouldn't affect the cold 0w side much at all, as VII only pushes up hot visc.
Good base oils and anti-ox additives in M1 0w40 keep hot viscosity from climbing upward.
 
Well, my wife's Mazda3 2.0 Skyactiv is spec'd for 0W20 in USA and Canada, but 5W30 in Mexico....USA/Canada - CAFE Standards. Mexico - nope. So, given it is a DI engine, my wife does short trips, I run Castrol EP 5W30 with a 5k OCI. I am concerned about engine longevity long after Mazda stops caring[60k miles].
 
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