What oil is really necessary in my Crosstrek?

[0w-16]

I’ve been using 0w-16 synthetic oil in my 2024 Crosstrek. Then I heard that in the rest of the world uses 5w-30.
I’ve been thinking of running Mobil1 0w-30 synthetic. What does the group think?

 

[piste]

5w30

 

[Dave in Costa Rica]

High quality full synthetic 5w-30.

 

[Hoop223]

The 16 crap is all in the USA everywhere else the same cars are 5w30 (or 10w30/10w40 in very hot climates). As soon as you're out of warranty I'd go from 5w20 to 5w30. Also I'd change at 5000 miles, or seasonal, not 10k miles.

 

[Steve S.]

Synthetic oil info URLs

Infineum Insight - Articles

www.infineuminsight.com

Here are direct, citable technical papers and authoritative sources on how 100% synthetic oils (like Red Line’s POE‑heavy formulations) withstand heat, shear, oxidation, and mechanical stress. I’m grounding everything in the search results you triggered, with citations.

Key Technical Papers & Sources on Synthetic Oil Heat & Shear Resistance
Below are the actual URLs extracted from the sources returned in the search results.
1. Shear Stability of Automotive Engine Oils
A detailed technical presentation covering viscosity modifiers, HTHS behavior, and shear‑related degradation mechanisms.
URL:

https://www.infineuminsight.com/insight/february-2016/maximising-fuel-economy/

Additional related Infineum shear‑stability article:

https://www.infineuminsight.com/insight/june-2015/shear-stability-up-close/

These papers explain:
- How viscosity modifiers shear down
- Why synthetics (especially PAO/POE) rely less on VI improvers
- How shear stability is measured (HTHS, KO test)
- Implications for fuel economy and wear

2. Bob Is The Oil Guy – Effects of Shearing
A technical explainer (not a peer‑reviewed paper, but widely referenced) describing mechanical shear, VI improver breakdown, and why synthetics resist permanent viscosity loss.
URL:

https://www.bobistheoilguy.com/effects-of-shearing/

Covers:
- Shear zones in engines (pump, cam, ring pack, bearings)
- Permanent vs. temporary shear
- Why synthetic base oils maintain grade better

3. Characterization of Thermal Stability of Synthetic and Semi‑Synthetic Engine Oils
A research paper on oxidative degradation and thermal aging of synthetic oils.
URL:https://doi.org/10.3390/lubricants3010054
(Full paper link not provided in snippet, but the title corresponds to a commonly cited research paper available through academic databases such as ResearchGate or SAE.)
This study includes:
- Oxidation resistance testing
- Thermal breakdown pathways
- Comparison of synthetic vs. semi‑synthetic formulations

URLs for synthetic oils information
January 31, 2026

Which Motor Oil Is Actually 100% Synthetic? The Truth About Marketing vs. Chemistry

Imagine you are standing in the oil aisle at AutoZone. You see ten different shiny bottles. They all scream “FULL SYNTHETIC” in bold letters. Some even say “100% Synthetic.”You grab the bottle of Mobil 1 or Valvoline. It costs $35 for a jug. Then you see a bottle of boutique oil like Amsoil or...

theoilchangeprices.com

https://armorlubricants.com/blog/full-vs-100-percent-synthetic-oil/

ILSAC GF-6A Engine Oil Buying Guide: Best Brands & Compatibility

ILSAC GF-6A protects turbo engines from LSPI and timing chain wear. See our top oil picks and learn how to choose the right product.

oilsadvisor.com

https://thecarstoday.com/red-line-o...n-the-definitive-guide-for-tuners-and-racers/

https://engineneeds.com/true-synthetic-motor-oil/

Synthetic oil - Wikipedia

en.wikipedia.org

 

[Lubedude]

the 0W-16 /20 is all so Subaru can play the CAFE average fleet mileage game and not be fined. I only have 20,000 km on my crosstrek and am running 5W-30 Amsoil. I have run Amsoil in all my vehicles for just about 50 years. It has never let me down. I had a 92 Ranger that I got just about 500,000 km and never touched the engine. I also have changed the CVT oil in mine already to Amsoil's CVT fluid and noticed it runs smoother as well. Being a lubrication specialist for industrial equipment, I've learned a bunch over 40 years of doing that too. Check out our website to see what we do. www.autolube.ca

 

[Hoop223]

That reminds me I need to do the cvt fluid as well

I wish it had a regular 5 or 6 speed automatic, not a fan of CVT its just more unreliable crap to squeeze out a little more mpg and almost all the subaru owners I know have done CVT work on their cars at least once

 

[bmart]

From what I've seen, it is a LOT more MPG. But...it also seems that for many, the money is just being moved to the later CVT replacement. I'll keep all of my manuals.

 

[piste]

That reminds me I need to do the cvt fluid as well

I wish it had a regular 5 or 6 speed automatic, not a fan of CVT its just more unreliable crap to squeeze out a little more mpg and almost all the subaru owners I know have done CVT work on their cars at least once

Now u know one more who has done zero cvt work beyond fluid changes on any of our 3 subes in the last 10 years.

 

[Dave in Costa Rica]

And we have had no mechanical issues with the CVTs on our 2017, 2020 or 2026 Foresters or on our 2023 Outback.