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5w20 vs 5w30

Old 01-10-2019, 12:35 PM
  #26  
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Use 5w-20

USA: 5w-20
HOT CLIMATES: 5w-30 (74F +)

Why?
If the oil grade is too thick it won't lubricate the contact between the APPEX seal and rotor housing.

Misconception: there's a misconception going around that thicker oil = more protection. This is FALSE. Stop putting heavy V6 & V8(XW-40+) oil on a freaking 1.3L tighlty compact engine. Trust me I followed this fad and that's how my first RX8 went to ****.

By the way: if you use THICK grade oil it will wear out your seals faster on COLD-STARTUPS. Trust me just use 5w-20 and pre-mix if your going to rip it in the Northeast states. It's how I maintain my RX8 as a daily driver and it fixed a bunch of my problems.

Tips: 5w-30 is a big difference from 5w-20 on rotary engines. We're talking really tightly compact engines. If the oil is too thick it's flow rate may be slower.

If your car is smoking blue on cold startups for a really long time MY POINT EXACTLY

EDIT: If your claim is to use heavier oil as a method to maintain cool temperature on the engine. You suck.. Get a better radiator, better oil coolers or an early fan trigger. If you go with a cheap option such as just using thicker oil you are going to get CHEAP results.

ALSO ALSO: I noticed from running several test that thicker grade oil has raised the engine load % on my engine.

Last edited by Eros Nunez; 01-10-2019 at 12:56 PM.
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Old 01-10-2019, 12:40 PM
  #27  
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Lets see your data to support the claim that 5w-30 won't adequately lube the apex seals.
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Old 01-10-2019, 12:51 PM
  #28  
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Originally Posted by NotAPreppie View Post
Lets see your data to support the claim that 5w-30 won't adequately lube the apex seals.
​​​​​​
5w-30 is perfectly healthy for summer drives but it will wear out your engine in the winter (40 and below)

My personal recommendation is:
Track: 5w-30(temps must be 65F+)
Winter/spring: 5w-20 + pre-mix if your ripping it.

Anything heavier than 5w-30 will cause friction between the seals. You must remember the space between the housing and the seals is VERY small. Thicker grade oil will just get dragged by the seals and not flow in between the seals and the housing. Which is what we want.
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Old 01-10-2019, 01:54 PM
  #29  
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Aside from reviving an 11-year-old thread...

I do agree that 5W-20 is adequate for cooler climates. This is what I use for spirited DD and occasional AutoX.

But some people have used XW-40 without issues, and in fact, I would use it if my car sees track time. You need that thicker oil for tracking where your RPM, load and temperature will be so high the thinner 20 oil will break down.

See the UOA thread if you want data.
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Old 01-10-2019, 06:58 PM
  #30  
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Ive been using pennzoil yellow bottle @ 10w40 as per the recommendation of several Rotary engine builders. Im in FL so weather is typically near HELL conditions but right now it does dip into the 30s-40sF in the AM startup. I wanted to switch to something thinner for winter temps but honestly... the pour point of the 10w40 is freakin -38F!!!! As per the data sheet. I dont think flow is an issue @ 40F in the morning. Lol.

I run the car HARD daily as soon as it warms up.
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