5-20 vs 5-30 oil - do I use it after 44K miles?
 

Hi All,

My RX-8 has +44K miles on it. I need to get more oil, and one shop said I should be using 5-30 after 25K miles.

Then I found numerous articles on engine failure due to using the 5-20 oil after various types of mileage.
Question: Should I put 5-30 in it, since it seems to run fine? Now I'm worried that my engine might fail if I don't switch.

Any comments are welcome.
Thanks
Bob S.

i believe mazda recomends 5-20, the climate in ur area will have a impact on what u should be runing, i use 5w-30 and will be switching to idemitsu 10w-30 next oil change, as far as what u should use? well i dont see a problem with either, mazda oil cap says 5w-20.. o btw 95% of technicians wont know shit about the renesis, ur fine with either one of thoose weights

Bob, there are alot of posts regarding engine oil in this forum. Please use the search function on the toolbar to find the appropriate answers. I'd suggest starting Here.

install the sohn adapter then run a w40 or w50 oil.

Thanks BM - T'll take a look at your link...
Bob

There is NO data relating to engine failure linked to 5w20 oil.

None.

There have been failures, usually directly caused by 'carbon lock' of the apex seal assemblies with consequent loss of compression, but oil viscosity has NEVER been a factor in an engine replacement......

Some dis-assemblies have revealed wear on bearings, consistent with the engine's mileage, but no definitive cause/effect has indicated that 5w20 is 'too thin'.

Generally speaking, a 'thin' oil will circulate faster, reach bearings faster, pass thru the filter sooner, cause less back-pressure, and - critically for the rotary - cool better.

These newfangled oils are not something to fear, (though those who routinely view everything thru a 'conspiracy theory' filter may obviously differ) they represent the latest and greatest in lube technology.
Indeed, they are basically impossible to make without using the latest synthetic basestocks and additives, rendering the old 'syn/dino' arguments moot.

......but if you live in the backwoods and "your pappy never used ought but 30 weight" feel free to use 1969's finest, it won't bother me. What do I know, thirty years in a refinery counts for nothing today.......

S

People who are tearing down engines recommend heavier weight oils as well as....

https://www.rx8club.com/showpost.php...&postcount=375

OK then, mine's an 2004 and it's had its share of things replaced under warranty (which is due to expire very soon), so I was concerned about which oil viscosity to use after looking locally (MV, CA) for a fair price for a "few" quarts of oil - guess I'll stick with 5-20; your point about the thin oil circulating better makes perfect sense to me...thanks!
Bob

i run 10w-30. ofcourse, who do you wanna listen to? the japanese Mazda who don't have to listen to Ford in Japan who recommends 5w-30 (and a bunch of different weights) based on temperature.

or are you gonna listen to USA Mazda operating with Ford with a mandate to improve fuel economy (if tat means running thinner oil so be it) that say from -infinity to + infinity temperature, 5w-20 will cut it?

at least that is what i think, i'll stick with the experts of rotary in japan on this one.

I never believed in 5w20, although people working everyday to improve current technology, but certain facts/properties cannot be changed, no matter how hard you work.

People always say "Oil Technology has been improved". hmm but ever wonder why engines from the 80s-90s outlast engines today ?

HKS japan sells Rotary oil with 10w45 or 10w40, they sell it for a reason, right ?

Going off topic again, meh.

OP's question's answer : I'll tell you to use at LEAST 5w30, Im using 0w30 right now, will switch to

Hey, love the intakes, but did it really improve perf? Where did u get the heads? I have an 04; not sure what I have...Bob

The K&N intake does improve some performance, but mostly just couple of hp. nothing major (no other intake gives ya major boost anyway)

I switched it back to stock cuz I want to keep the noise low, I mean Im ok with it, but some *female* who always in my car has been complaining since day 1, listening to her everyday made me loose part of my hair ... anyway, one day I will go back to K&N, just gonna enjoy the "quietness" that stock intake gives me for a while.

as for your original Question, nothing less than 5w30. Im thinking to switch to 10w40 after my 0w30 runs out.

I will put it this way. You will not catch any Japanese rotary tuner put 5w-20 in an RX-8. They use 0W/5W-30 or higher. The Japanese Mazda dealers put in 0W/5W-30 in the RX-8s.

Make of that, what you will.