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

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.

 

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 65°F+)
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.

 

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.

 

 

My engine builder told me yesterday to get 10-40 for the engine hes currently doing for me. I also live in Central/south FL so Im going to be doing this as well. I first thought it might be too thick but I let the car warm up for a good 5-10 mins before I go anywhere. And the car parks in the hot sun so its always over 90 degrees under the hood.



sorry pics are so BIG!

 

Heck, in Florida you could probably go with 20w-40 or 20w-50.

I disagree with your engine builder that you should let it warm up for 5-10 minutes before driving it. The period from cold start to warm up is when a large amount of carbon is produced. Doing things to minimize this time (i.e. driving while keeping the RPM's under 4-5k) is a good plan.

 

Warming up the car for 5-10 minutes accomplishes only one thing: wasting fuel.

 

Ok, thanks for your input. In his defense, he never told me to let the car warm up for 5-10 (just the part about 10/40)

 

Me not reed gud.

 

Love my 5W-20, now in its 14th year of exclusive use in my ‘05 RX-8. ❤️

 

Are we rehashing the oil wars again? Mobil 1 0W40 for me, changed every 3K miles, with a filter change every 6K miles.

Sure, but don't you have something like 5 miles on your car?

.

 

I currently have 60+k and I am sure my car has only ever seen 5W-20. Works fine. I don't track or live in a hot climate, though.

 

Yeah, something like 5 miles. Lemme check... oh, 47.5K miles. You’re only off by 46,995 miles. But hey, why let facts get in the way of a long-standing false rx8club.com narrative, right?

 

Mileage is what matters. Fourteen years is a great run, but 48K miles is pretty close to half the expected lifespan of the Renesis, according to several engine builders. My 2011 has 45K miles, and many are hard track miles. One recent compression test has the engine as average or barely failing, depending on whether you believe the equipment normalized the results. This is pretty much inline with the expected lifespan. I am taking it out for a 3 day Italian tune-up this weekend, then to a different dealer for another compression test to hopefully discover the truth.

I'm not a hater; I love my 8. But, I do deal in facts, and many people would expect a 14 year-old car to have ~160K miles on it. Forty-eight thousand is much lower than average for a car of that age, and I find it a bit disingenuous to report only the car's age.

.

 

So, in other words, 14+ years ownership without a single engine problem doesn’t really count if there are only 47.5K miles on the car. 14+ years ownership with no engine problems is only meaningful if said car has 160K miles on it. Or, put another way, 47.5K miles with not one engine problem ain’t news for the Renesis if I took my time racking up that mileage. Because... because... having many days off between rides gave my car time to magically heal itself of any developing compression issues! Instead of my seals wearing down like so many Renesis seals allegedly do (well, the ones we read about on internet forums, anyway), mine, sitting quietly in a dark garage for four, five, six, maybe ten days between rides, had a secret advantage! They could magically restore... yeah, that’s it, restore themselves back to spec, not unlike the way Christine could heal and renew herself overnight in what I used to think was a fictional movie!!!

Got it.

 

Steve actually has a point. 48k miles are very low considering a 14+-year-old car.

There are parts that are more related to age, like a bunch of plastic parts(although more heat cycles still would break them faster) and brake fluid, but engine wear is definitely mileage related. The less you drive it, the less wear there will be. There are zero problems I see with that logic.

No one said your car will magically heal itself. The point is that your car will very likely have less wear than Steve's or my car because we have more mileage.

And there is a reason oil threads always go to ****. Just realize each person's use case is different so one choice that works for one person won't work for another. As long as you have a valid argument behind your reasoning, keep doing what you are doing, and just agree to disagree with others.

 

10w 40 in my 05 RX8, weekend runner only as I have a work vehicle so look forward to my weekends big time to put my baby through her paces.

 

Mine is coming up on 130k miles. I bought the car with around 70k miles, still original engine. Only ever used 5w-20.

I try to keep oil change frequency to around every 7,000 miles.

I'm debating whether to even pursue the Sohn modification at this point.

 

I don't get it, are you arguing against your own point?
If you don't drive the car, the seals don't deteriorate. So the only thing that matters is mileage, of which you have an unremarkable amount to claim some superiority over other owners whose engines have failed, or over the notion that engines fail.

 

And speaking of seals... I think oil won't make as much of a difference once sprayed into the combustion chamber. The bearings will be more sensitive to the viscosity of the oil.

 

sweet mother of pearl... and here I am doing quick drain n fills every 1,500 miles (leaving the oil filter alone for several more oil changes) with 10w40 to insure adequate viscosity at all times. Hmmmmm.

 

Mine sees track days and autocross several times per month for 9 months of the year. I run Castrol Syntec 0W-40 changed every 2k miles with a filter every 4k.

 

So then 47.5K+ miles with not a single engine problem to date is about right for the Renesis.

Got it.

 

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