Thick (20W-50) vs Thin (5W-20) Engine Oil Tested

**Dr.Kamiya** · June 16th, 2024 08:33 PM

Interesting points (skip to the 32 minute mark of the video to jump to the conclusions section):

The oil gets contaminated with water if the filter is not pre-filled with oil prior to installation. This happened with both the 5W-20 and the 20W-50:

The thin oil shows increased wear because of this contamination:

The thick oil, even when not pre-filled does not show increased wear:

In all cases the thicker 20W-50 oil offers MUCH more protection than the 5W-20. The thin oil exhibited increased iron in the oil in every scenario, and in particular after doing a power run on the dyno had 61ppm iron, compared to just 21ppm with the 20W-50. The hosts said that this mean the thick oil is giving 4x as much protection as the thin oil (or perhaps that the thin oil is showing 4x as much wear as the thick oil. I didn't question the maths).

**Vodka** · June 16th, 2024 08:45 PM

i watch that youtube channel. interesting results. the jimny is ok to use up to 20w40. maybe i should start using thicker oil if i plan to keep the car for a long time... i'm already using slightly thicker transfer case and differential fluids

**travajante** · June 17th, 2024 01:20 AM

Originally Posted by Dr.Kamiya

Interesting points (skip to the 32 minute mark of the video to jump to the conclusions section):

The oil gets contaminated with water if the filter is not pre-filled with oil prior to installation. This happened with both the 5W-20 and the 20W-50:

The thin oil shows increased wear because of this contamination:

The thick oil, even when not pre-filled does not show increased wear:

In all cases the thicker 20W-50 oil offers MUCH more protection than the 5W-20. The thin oil exhibited increased iron in the oil in every scenario, and in particular after doing a power run on the dyno had 61ppm iron, compared to just 21ppm with the 20W-50. The hosts said that this mean the thick oil is giving 4x as much protection as the thin oil (or perhaps that the thin oil is showing 4x as much wear as the thick oil. I didn't question the maths).

Good thing you don't have an oil pressure gauge. It'll make you think twice about going 50.

**Dr.Kamiya** · June 17th, 2024 09:09 AM

Originally Posted by travajante

Good thing you don't have an oil pressure gauge. It'll make you think twice about going 50.

Out of sight, out of mind!

Seriously though oil pressure was addressed in the video, both inital ramp up from cold start (from the start of the video) and dip in oil pressure during power runs (*21:50).

**oj88** · June 17th, 2024 10:23 AM

My Diesel asks for 5w30 so I'll try to switch back to that after the break-in. Currently on regular Toyota 15w40.

I am also inclined to do yearly OCI using Amsoil Signature Series Max Duty 5w30 instead of the Toyota FS 5w30 (4 to 6 months OCI).... they're almost the same price if you get the latter from the dealer.

A UOA would be nice, if they were that common and not so expensive.

**dr. d** · June 17th, 2024 04:45 PM

Originally Posted by Dr.Kamiya

The oil gets contaminated with water if the filter is not pre-filled with oil prior to installation. This happened with both the 5W-20 and the 20W-50:

The thin oil shows increased wear because of this contamination:

The thick oil, even when not pre-filled does not show increased wear:

In all cases the thicker 20W-50 oil offers MUCH more protection than the 5W-20. The thin oil exhibited increased iron in the oil in every scenario, and in particular after doing a power run on the dyno had 61ppm iron, compared to just 21ppm with the 20W-50. The hosts said that this mean the thick oil is giving 4x as much protection as the thin oil (or perhaps that the thin oil is showing 4x as much wear as the thick oil. I didn't question the maths).

i have a theory,
if the oil filter is not primed (filed up prior to installation),
the initial seconds of the started engine will have moments of poor lubrication to the friction surfaces, because these first seconds are used to fill up the oil filter first, before the oil can go up to the oil galleries and lubricate the moving parts.
but why only thin oil? my theory is, there might be significantly more residual thick oil between the metal friction surfaces, compared to thin oil...

but i am curious,
where does the water come from?
and if there is water, why no glycol...?

so bottomline,
if the 20W oil seem to do a better job in the longer run,
what oil grade does the manufacturer recommend to us tropical motorists?

**Dr.Kamiya** · June 17th, 2024 11:08 PM

Originally Posted by dr. d

so bottomline,
if the 20W oil seem to do a better job in the longer run,
what oil grade does the manufacturer recommend to us tropical motorists?

Before the power run both filters are already primed so pre-fill should no longer be an issue, but the thicker oil offers much better protection in terms of valvetrain and cylinder oil wear (Iron), and bearing wear (lead).

For our weather I think thick oil is better. It's cold weather where a low "W" rating had an advantage because it flows better during very cold starts, but we don't really have that problem here when it's 25-35C year round. You can try pouring some oil out of a container in the coldest months of December to Febuary and it will flow well.

But the video did say follow the manufacturer recommendations. The particular engine they tested with is an old-school V8 and does not have tight tolerances.

Anecdotally, I run DEFI meters for oil pressure, oil temp and water temp and didn't really see big differences in oil pressure between Shell Helix 10W-40 that the casa liked to use, vs HKS Turbo 15W-50 that I switched to after the car got a big turbo and tune. I did see a marked drop in oil temps during high load, but the EJ2xx is also an ancient engine that dates back to 1989 so I wouldn't be surprised if it was designed to take thicker oil which was the norm back in the day.