Summary of "Should You Thicker Oil In Your Modern Engine To Improve Reliability?"

Main conclusion / verdict

Follow the manufacturer’s recommended oil viscosity. Don’t switch to a thicker oil unless the OEM explicitly instructs you to. Thicker oil is not a reliable long‑term fix for design or manufacturing defects and can void your warranty. Prioritize proper maintenance (timely oil changes, quality oil, addressing short‑trip/moisture issues). Maintenance quality and engine design/manufacture matter far more for longevity than small changes in oil weight.

Key points about thin vs. thicker oils

Manufacturers test and validate engines using specific oil grades for each market and climate; the recommended oil is part of that validation.
Modern thin oils (0W‑20, 0W‑8, etc.) were introduced mainly for emissions and fuel‑economy reasons. Thin oil itself has not been shown to universally reduce reliability when the engine is well designed and maintained.
Thicker oil can raise oil pressure and may sometimes be used as a temporary “plug” to reduce symptoms — but this can mask the underlying problem rather than fix it.
Using a non‑recommended viscosity can jeopardize warranty coverage if a failure occurs and analysis shows non‑OEM oil was used.
Most engine failures (examples: some Toyota V35A/Tundra and certain GM engines) stem from design or manufacturing defects, debris, clogged passages, or poor parts — not solely from oil viscosity. High‑quality oil cannot prevent failures rooted in those issues.
Short trips and moisture contamination (fuel dilution, sludge, water buildup) are major killers of modern engines and typically cause more harm than thin oil alone.

Practical recommendations (maintenance & user experience)

Stick with the OEM viscosity unless the manufacturer explicitly tells you otherwise.
Oil change guidance:
- Typical use: aim for no more than 5,000 miles between changes.
- Turbo engines: consider 4,000 miles or even 3,000 miles for extra margin.
- Time limits: about 6 months for general use; less for turbos; as short as 3 months for repeated short‑trip duty.
If you do many short cold trips (frequent start/stops, low weekly miles), change oil more frequently because fuel and moisture buildup accelerate oil degradation.
Use quality oil. For Toyotas the speaker recommends OEM Toyota oil or Mobil 1. Be aware that dealers and quick‑lube chains may use cheaper oils even when you think you’re getting OEM.
Don’t assume dealerships always use OEM fluid — discounted oil changes usually imply lower‑grade products.
Thicker oil will not “fix” an engine that burns oil due to mechanical wear — burning oil is a symptom of mechanical problems, not a viscosity issue.

Pros and cons of switching to thicker oil

Pros (possible, limited)

May raise oil pressure and temporarily reduce some symptoms.
Could be used as a short‑term stopgap in certain recall/fix programs if the manufacturer advises it.

Cons

Can void or complicate warranty claims if the manufacturer specifies another viscosity.
Does not address root causes (design/manufacture defects, clogged passages, debris).
Can give a false sense of security and delay proper repairs.
Can be used as a cheap expedient by manufacturers/dealers instead of performing proper fixes.

Comparisons and examples mentioned

Common grades cited: 0W‑20 and 0W‑8 (Toyota examples) versus oils like 5W‑30, 0W‑60, 15W‑50 (diesel/other markets). Different markets/climates and emission rules drive different OEM recommendations.
Examples show wide variation: some Toyota engines have reached 300k–400k miles on 0W‑20; others developed sludge by 50k miles — demonstrating that maintenance, build quality, and operating conditions matter more than viscosity alone.
Manufacturer responses vary: some recommend thicker oil as a temporary measure, others perform part replacements or more substantial repairs.
Chain‑tensioner and similar problems are often linked to clogging or lack of maintenance; thicker oil might temporarily mask symptoms but won’t cure the underlying issue.

Unique points (highlights)

Manufacturers test engines using specific oils for the markets/conditions where cars are sold.
Emission regulations in different countries cause OEMs to recommend different oil viscosities for the same engine.
Modern thin oils are physically noticeably thinner than older grades.
Reliability differences are driven more by engine design and manufacturing quality than by oil weight.
Using non‑recommended viscosity gives manufacturers legal cover to deny warranty claims.
Dealers and quick‑lube chains commonly do not use OEM oils despite customer assumptions.
Cheap or discounted oil changes usually indicate lower‑quality oil is being used.
Moisture and fuel dilution from short trips accelerate oil degradation and engine problems.
Most everyday drivers are behind on maintenance and are therefore at greater risk than enthusiasts who maintain their cars diligently.
Frequent short trips over years can ruin modern engines through fuel/moisture buildup and sludge.
Turbocharged engines require shorter oil‑change intervals.
Thicker oil will not cure mechanical problems like burning oil, clogged tensioners, or defective bearings.
Some manufacturer “fixes” that change oil weight are effectively temporary patches.
Good maintenance (regular changes, quality oil) can prevent many problems regardless of viscosity.
The speaker’s personal practice: uses OEM oils (0W‑20/0W‑8) in his Toyotas and a 2024 Tundra hybrid and is not worried about thin oils when properly maintained.

Different viewpoints referenced

Video speaker (mechanic): Recommends OEM viscosity, stresses maintenance, calls thicker‑oil fixes a plug, recommends OEM or Mobil 1, and gives oil‑change interval guidance.
Motor Oil Geek: recommended as a resource for deep oil chemistry knowledge.
Engineering Explained: suggested for engineering detail and testing methodology.
Forum/owner anecdotes: many owners recommend different oils based on personal experience (some use 5W‑30 instead of OEM 0W‑20/0W‑8).
Manufacturer actions: GM reportedly recommended thicker oil as part of some responses (viewed by the speaker as a cheap patch); Toyota has issued recalls/fixes for some engines including part replacements in some cases.
an AI‑generated video: claimed thin oils destroy engines; the speaker dismisses this as overblown.

Bottom line recommendation

Do not thicken your oil as a general reliability fix. Use the oil grade your manufacturer specifies, prioritize timely oil changes and quality oil, and address mechanical or manufacturing issues through proper repairs rather than changing viscosity as a workaround.