Engine Oil for High HP Rotarys 2018. Whats acceptable?
 

Numerous threads on here regarding engine oil, but I have seen any updates in recent years. I am aware and have been using the seemingly #1 choice, Castrol GTX 20/50. However, I've not been able to get this locally(outside the US) lately. Also, there are several newer brands on the shelves these days. What else are you guys using in the 20/50 grade that is acceptable for my high HP rotary?
Some of the brands I have access to: Formula Shell, Valvoline Premium, Total, Xcell, Mag1, Coastal, and Tekstar.

What brand are you using?

I've always used Redline 50 weight racing oil though that's only because it's what we always used in E production and on engines we were winging to 9.5k+. Not because of crazy power numbers.

Uhh, definitely interested here too. I'm thinking along the lines of Rotella T6 5w-40, or if I need more oil pressure I can find a Euro oil equivalent.

A long but interesting read: https://540ratblog.wordpress.com/201...-test-ranking/

Tempted to try out the Renewable Lubricants, Bio-SynXtra in 10w-30.

I think our oil pressure is too important for such a thin oil.

Why not used the oil that was developed for the engine?
20W50 at Idemitsu Lubricants America Corporation

And use their premix in the gas.

Read section two of that engineers blog. It discusses oil pressure vs oil flow and points out it's not oil pressure that separates bearing surfaces. Makes sense that we would want maximum flow through bearing surfaces where a thinner oil will always flow better however we must make sure there is enough pressure to keep the bearings fed.

Over the years I would always see the 20w-50 recommendation because of fuel dilution in the rotary. Only proper testing would show if this really is the case in a healthy motor, which I have not come across.

This has to be one of the few questions that are truly difficult to answer as there are too many brands and weights out there. What you should start with is a synthetic oil with a high base stock grade and then narrow your choices through oil tests lab data given through the manufacturer.

Personally, I run Schaeffers 5-50 Supreme 9000 which is considered a racing oil. It has loads of zinc and moly and high lubricity content. Another nice thing about it is that it's known to keep surfaces clean of varnish and help keep your oil system clean. The only problem is that it's hard to get. I've seen higher pressures and slightly cooler temps with the oil since changing from a 20-50. In piston engines, people have seen oil change intervals upwards of 10k miles. My salesman has been sending in tests and changes around 12k.

I would do some research as there's a lot that goes in to good oil and you'll most likely be good with anything you pick.

I have not try Idemitsu oil but i have use castrol and valveoline and Mobil syentec and I find that Amsoil oil and it out perform all of them. I am hitting close to 2k miles on my amosil synthetic and the oil is stilll like new. I used the turbo signature series 10 w30 or 40 weight can't remember and I dont baby it either.

I happened to have Amsoil available locally, so tried it after Mobil1 seemed to stop selling 20/50 and really like it. Based on the motor oil, I tried their gear oils as well—including their 70/140 weight that I put in the diff to keep it from breaking down and leaking on track until I get a dedicated cooler setup.

My understanding is mutli weight oil is really the lower weight with additives to acheive the characteristics of the high weight, i.e. 10W-40 is a 10 weight oil with addititives to acheive a 40 weight oil. It is also my understanding that the lager the spread betwen the low weight and the higher weight are more prone the oil is to breaking down so it needs to be changed more frequently to keep the characteristics of the higher weight oil

Currently i run Motorcraft 5-50, but thinking about Mobil 0W-40 FS (Euro spec)

This

You also have to consider that the "hot" weight is also usually based on an oil temperature of 100C. So if you are racing and your temps are getting higher than 100C (hint: where you measure the temp is important) the oil viscosity will be lower. I usually run a 20w-50 at the track and 10w-40 in my street car. So it really depends on your personal use case but for street use, any SAE oil from any of the major brands will work.

Ugggggh. I worked as an engineer at an R&D facility doing fluid film bearings - long story short, that guy's testing is really relevant to the lifters on flat tappet engines (like say, the big block Chevy) but isn't as relevant to the rest of the bearings in the engine. He didn't want to acknowledge that non-BBC engines had different failure modes because what he always saw fail was lifters.

540rat used to have an oil thread on speedtalk, until his methodology was debunked as spurious at best.

In all fairness, his methodology is fine for one specific sort of thing - it does a good job at looking at boundary lubrication. For highly stressed flat tappets like on a BBC drag engine, that's a weak point. For many other things you can actually fail the fluid film bearings.

I'll have to test oil viscosity once I get the engine dyno going. I really really want to try to do some temperature measurements at the rotor bearings on a 13B - I have some strong suspicions.

Rotella 15w40 bearings are always perfect just change it more often it's cheap anyways.