Lots of us use 20w50... Are we mistaken?
 

Not much experience with 3rd gens, but in both the 1st gen and 2nd gen circles the recommended oil is Castrol GTX specifically in the 20w50 weight.

This article:
http://grassrootsmotorsports.com/art...lippery-slope/

appears to contradict that for a stock, daily driven RX-7.

The article didn't specifically address rotary issues, most notably high heat... But I'd think Mazda engineers would have thought of that.

The one thing that I don't think anyone can take into account is dilution by fuel which would vary based on how often you flood the engine.

Anyone have thoughts?

I dunno, man. Since 1986, I have been running 20w50 in all of my rotaries. Most of it has always been Castrol. But, for nearly the past 10 years, I have been running full synthetic (obviously premixing) with great success. I've ran the synthetic in anything from a mild street port NA all the way to a N2O breathing bridge-port screaming at 10k rpms....and I drove this car for over 2 years everyday with no problems what so ever. Same thing for all 21 other rotaries that I have owned and driven...no problems with the 20w50.

As you mentioned, the article didn't specify anything rotary...or many other factors. I'll stick with my 20w50.

Well I use 20w50 in my FD in summer time, and 10w30 in winter, but my RX-8's owners manual recommends 5w20... I don't know why, but I'm not going to argue with Mazda on the issue. They've been doing rotaries since before my mom was alive.

I currently run 15w-40 Dino oil in my car but now that I deleted the MOP I was going to switch to 10w-40 synthetic.
I currently see oil tems between 140 and 170 during everyday driving depending on outside tem, 180 degrees in extreme cases.
I am really interested to see what they go to with the synthetic.
A lot of the stuff they write makes a lot of sense, but while piston engines lose power with heavy oil due to the crank windage problems ( crank hitting the oil), we dont, and I think we would lose minimal power with the extra oil pump strain, so we lose less power by running heavy oils.
Great article, +1 for you.
I'll save it and keep it in mind after I hit the track.

5w20 is made from a better base oil than 5w30. It is closer to a low grade synthetic in a conventional package.

I just wanted to mention that I've been running synthetic with my working OMP since 2001 :)

i have been using 10w40. I think im gonna go back to 10w30 and do some oil temp logging.

What brand?

I've been a proponent for NOT using 20w50 on the street. I just don't see the purpose other than to overwork the car for no real gains. Most owners use "fuel dilution" as their reasoning for the heavy weight oils on the street. I do use 20w50 for summer track days, but for the street I use 10w30.

5w30 synthetic as recommended by Howard Coleman :D

i now use 10W30 or 10W40 synthetic in all my cars! i've been doing this since 2003. i read a couple of articles by Redline and Amsoil and i gleaned enough information to feel justified in my decision to switch from my old mineral 20W50 ways - to the point where i even sell Amsoil now.

Ive always ran the 20w50 mineral in mine. I wont use castrol though. But yea, premixing and all when the last motor came apart it looked gorgeous on the inside. So I see no problem using it.

http://www.ferrarichat.com/forum/faq...=haas_articles

I always post this article in discussions about oil weights, because it's a very misunderstood subject, and Dr. Haas does a good job of explaining things. I normally run 5W-30 unless the engine has low oil pressure, like the one in my FB does (in which case I run 10W-40). I'd use a nice 0W-30 synthetic, but with as often as I change my oil, I can't justify the extra cost.

In my opinion two of the best gauges to have are oil pressure and oil temp. Among other uses, they make it easy to see the effects of different oil weights.

Shell Rotella 15w40 is probably the best non-synthetic oil for a rotary. It's thick enough for the giant bearings rotaries have and much higher quality than the castrol GTX.

There was an article on breaking down the stats in oils...GTX scored VERY high for a non synthetic. I run GTX 10W30 in the all but summer, where I use 20W50. OMP blocked off, premixing...I get so much blow by with the turbo though and fuel dilution is horrible, so I change my oil every 2000 miles. If I didn't have such bad fuel dilution I'd use a nice 5W30 or 0W30 full synthetic and change it every 3000 miles.

I don't quite get the obsession some people have with running heavy oil. Lighter weight oil leads to better fuel economy and better power, so why not run the lightest weight oil that provides adequate protection? If it calls for 5w30, can you get away with 0w20? 0w30?

0W-30 is fine, because at operating temp it behaves like any other 30-weight oil. It just won't put as much wear on the engine during cold starts. Some of the RX-8 guys running 5W-20 have apparently experienced higher bearing wear compared to 5W-30, so I'd avoid 20-weight oils for now until we get more long-term data. It's suspected that Mazda specified a 20-weight oil so they could claim better fuel economy or emissions numbers for the RX-8.

I thought synthetic wasnt a threat to the omp just that it doesnt burn when injected into the motor? Just curious*

-Chance

I think you have your numbers swapped. the first number is the weight... correct? the second number is the viscosity?

So 5w-30 is 5weight
0w-30 would be 0w?

No. Read the article I posted, it explains the meaning of the numbers. In a nutshell, the second number tells you the weight of the oil; the first number we just want to be as low as possible.

This is a myth. Modern synthetics burn just fine.

Yeup, 10w30 is better than 20w50 for most NAs. Fortunately it's not a serious problem in most cases. Just a little more wear and a little less mpg. I used 10w30 myself. 5w30 or 10w40 aren't quite as good as the weights that have a smaller ratio between the numbers because they have more impurities to achieve the large ratios, but they're still ok.

No, both numbers telling you how oil flow at given temperature. Low first number is good for cold start, very cold weather... lowers wear at start-up etc...

This makes a lot of sense to me.

Thanks for the article. Interesting reading.

I bet most of you dont even use an additive like zddp plus but are still worried about what weight.

Thank you for the correction. I got myself all mixed... and on something relatively simple lol.