Who's right? (or closer to right): Oil specification for my old Fiat Abarth, 5w40 or my new Honda SI, 0w20?

[Zaedock]

It’s the 0W that freaks people out.

I like it, because it gets into the nooks & crannies of the engine.

 

[kschachn]

As does any other oil with a different winter rating, being completely dependent on temperature. The winter rating is only relevant at cold start and an oil with a 0W rating is only guaranteed to be different in that regard at temperatures below about -30. Once the engine is started and the oil starts to warm up even a tiny bit then the situation changes.

 

[wemay]

Report

 

[wemay]

Sorry, did not mean to call into question anyone's attention span, etc.

 

[ultraviolet]

It’s the 0W that freaks people out.

it's definitely the 20 that gets me, 0w40 is my favourite oil! sae20 is just too thin of an operating viscosity.

 

[PimTac]

it's definitely the 20 that gets me, 0w40 is my favourite oil! sae20 is just too thin of an operating viscosity.

And that is your OPINION, not fact.

 

[Bill_W]

Seems I have a choice between 0w-20 and 5w-30 for my 2019 Miata. I choose 0w-20… No worries here. In fact I like the HP gain.

 

[PimTac]

Seems I have a choice between 0w-20 and 5w-30 for my 2019 Miata. I choose 0w-20… No worries here. In fact I like the HP gain.

These engines are dandy. It is the smoothest running four banger I’ve owned. I like the fuel economy as well. I’m getting over 30mpg on winter grade gasoline and it just went up another nickel today at the pumps.

 

[FTTSHO]

These engines are dandy. It is the smoothest running four banger I’ve owned. I like the fuel economy as well. I’m getting over 30mpg on winter grade gasoline and it just went up another nickel today at the pumps.

Yep, my buddy has a 2018 Miata 6 speed manual. It's an absolute blast to drive, and gets amazing fuel economy. Literally costs him $20 every other week to fill up at the gas station. It's a smart daily driver to own, except you can't fit anything in the small trunk it has.

 

[Bill_W]

Yep, my buddy has a 2018 Miata 6 speed manual. It's an absolute blast to drive, and gets amazing fuel economy. Literally costs him $20 every other week to fill up at the gas station. It's a smart daily driver to own, except you can't fit anything in the small trunk it has.

It got 26 more horses due to higher redline in 2019.

 

[kschachn]

Oil analysis' aren't very accurate, but there is no universal proof that using 0w20 increases wear.
Anyhow, my engine is fine, I have done 2 oil analysis tests through Blackstone labs at 50k miles and 80k miles, and my engine did way better than the universal average for my engine when I used Royal Purple 0w20 for 5,200 miles. 0w20 doesn't increase wear even in my twin turbo engine that is notorious for having bad fuel dilution issues. The fuel dilution number was less than 2.0% when I did the test, which is pretty good for this engine. 20 weight is not a problem.

It’s not so much that a UOA is inaccurate, it’s that it doesn’t really test the oil. Instead it gives a snapshot into the engine design, condition and your particular operating conditions. Very little in a UOA tells you anything about how an oil performs. You have a far more fundamental problem than just the accuracy of the test.

 

[Trav]

it's definitely the 20 that gets me, 0w40 is my favourite oil! sae20 is just too thin of an operating viscosity.

How so? If the bearings load surface is sufficient, the clearances are correct, the crank Ra finish is correct and the oil pump is tailored to lower viscosity oils there is no issue whatsoever using it. Other engines like the eg older BMW M engines may experience premature engine bearing failure on thin oils. You cant paint with a broad brush.

 

[Bill_W]

How so? If the bearings load surface is sufficient, the clearances are correct, the crank Ra finish is correct and the oil pump is tailored to lower viscosity oils there is no issue whatsoever using it. Other engines like the eg older BMW M engines may experience premature engine bearing failure on thin oils. You cant paint with a broad brush.

20 weight oils were made for the engine design. First came out for Ford and Honda in 2002. 20 years of engines designed for 20 weight oils.

 

[OVERKILL]

20 weight oils were made for the engine design. First came out for Ford and Honda in 2002. 20 years of engines designed for 20 weight oils.

Aye, but a lot of the engines that spec'd xw-20 in the early 2000's were originally spec'd 5w-30, like the 2V Modular. It was through testing (that I touched-on earlier in the thread) that it was determined that xW-20 would also be appropriate.

 

[kschachn]

Aye, but a lot of the engines that spec'd xw-20 in the early 2000's were originally spec'd 5w-30, like the 2V Modular. It was through testing (that I touched-on earlier in the thread) that it was determined that xW-20 would also be appropriate.

Yep and that's due to the fact that a 2.6 HT/HS is on the cusp of increased wear without material or design changes. It's what most engines can get away with, most of the time. Those engines weren't designed for 20-grade oils as much as they allowed their use. Even my old 1MZ-FE and 1NZ-FE engines were back-specified to 20-grade oils.

 

[Bill_W]

Aye, but a lot of the engines that spec'd xw-20 in the early 2000's were originally spec'd 5w-30, like the 2V Modular. It was through testing (that I touched-on earlier in the thread) that it was determined that xW-20 would also be appropriate.

Now the 0w-20 oils are much better than 20 years ago. And the engines are designed for the 0w-20 viscosity oil.

 

[kschachn]

Better in material properties and requirements such as oxidation resistance and so forth, but better in HT/HS or the resulting MOFT? That's what really determines use here and in older engines where the grade is back-specified.

 

[OVERKILL]

Yep and that's due to the fact that a 2.6 HT/HS is on the cusp of increased wear without material or design changes. It's what most engines can get away with, most of the time. Those engines weren't designed for 20-grade oils as much as they allowed their use. Even my old 1MZ-FE and 1NZ-FE engines were back-specified to 20-grade oils.

Yep, that's correct, I touched-on that earlier in the thread. It was found that once you got below 2.6, you needed major design changes and special coatings.

 

[OVERKILL]

Now the 0w-20 oils are much better than 20 years ago. And the engines are designed for the 0w-20 viscosity oil.

Yes, and one of those design changes has been the widespread fitment of coolant/oil heat exchangers to control viscosity.

 

[Slow Car Sport Mode]

Yep, that's correct, I touched-on that earlier in the thread. It was found that once you got below 2.6, you needed major design changes and special coatings.

Would it be logical to assume, then, that the xW-20 oils specified by manufacturers would tend to be at or above the 2.6?