How many times have you switched sides on the thick vs. thin debate?

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When I started out in motor oil I used to be a thin guy and thought thin would be the best for Canadian cold starts.

Then I started researching euro spec oils and thought HTHS was the best measure of engine protection combined with an additive package capable of extended OCIs.

More recently I've been learning about base stocks and viscosity improves, as well as re-visiting the Motor Oil University, which is bringing me back to the thin side. So I switched sides twice on the thick vs. thin debate.
 
If an engine will last 200k with 0W20 will 10W40 make it last 400k?
Since the rest of the vehicle falls apart too its questionable and engine dependant.
Does it matter if your engine lasts 400k if your subframes rot off.


My opinion:
Too thin or thinner than recommended MAY damage engines or cause excessive wear.
too thick does not damage engines.

This is being reasonable.
no one is talking about using 0w8 in a 5w30car or 25w70 in an alaskan prius use common sense.

OTOH using 5w20 on a track day in a mustang can be just as bad as using 20w50 in -30f.

no one oil is perfect for every car, situation, and use.
 
Since the rest of the vehicle falls apart too its questionable and engine dependant.
Does it matter if your engine lasts 400k if your subframes rot off.


My opinion:
Too thin or thinner than recommended MAY damage engines or cause excessive wear.
too thick does not damage engines.

This is being reasonable.
no one is talking about using 0w8 in a 5w30car or 25w70 in an alaskan prius use common sense.

OTOH using 5w20 on a track day in a mustang can be just as bad as using 20w50 in -30f.

no one oil is perfect for every car, situation, and use.
I was playing devils advocate. I use what the manufacturer specs. I never used to care about that before having an engine with a two stage oil pump, piston cooling ports, and AFM setup.
 
When I started out in motor oil I used to be a thin guy and thought thin would be the best for Canadian cold starts.

Then I started researching euro spec oils and thought HTHS was the best measure of engine protection combined with an additive package capable of extended OCIs.

More recently I've been learning about base stocks and viscosity improves, as well as re-visiting the Motor Oil University, which is bringing me back to the thin side. So I switched sides twice on the thick vs. thin debate.
I pretty much started out on the same path as you back in 1975 with Mobil1 5w-20. I've gone back and forth but my latest experiment with xW20 has me back to using the higher HTHS lubricants.
 
I've been thick and I've been thin (poor) but thick is better.
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If an engine will last 200k with 0W20 will 10W40 make it last 400k?
The engine in my '88 Ford Escort running 10w40 had 518K miles when the car was retired at 20+ years old for other issues. I can't say whether it would or wouldn't have lasted as well with 0w/5w-8/16/20 because I never used them and probably never will. No reason to mess with what's worked for 45+ years.
 
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