What is the best Oil to use in a Rotary Engine?

[Johnnyboy]

Hi Guys.

A new slant on this for we Elford folk.....

As some of you may know, I am currently working with a bunch of automotive design engineers and the lunchtime conversation eventually got around to Miss January, thence to Turbo Rotaries and oil.

(I think I lost them at one point by mentioning that Miss January had a Garret T2 turbo (Elfords were, wern't they?) and had an SU carburettor and they did a bit of rolling about on the floor laughing much the same way my IT friends do when they realise I have a mobile phone that does not do the internet.)

Just to be clear, these guys don't work with rotaries and only know about them from old books (!). However they DO know a lot about turbocharging and supercharging and have a view that I think I should share with you.

Basically they were horrified at the thought of lubricating a turbocharger with Mineral oil.

They spent at least 20 minutes talking between themselves about molecules, bond strengths and film thicknesses (my ears pricked up at the mention of James Bond films but they are surely available on DVD these days?:? ). Then they said "DON'T USE MINERAL OIL IN A TURBO" (I use capitals because they spoke very slowly and clearly to make sure I understood).

Apparrently the environment in the gubbins of a Turbo is very harsh indeed, with very small clearances, and you need the best lubication you can get.

I told them the problem with deposits on the rotor tips and they were sympathetic but seemed to regard oil-in-the-petrol as being akin to polluting rivers with untreated sewage and then complaining the water tasts funny (told you they didn't work on rotaries didn't I...) and had no advice to offer.

So. Their point is that although a rotary might be happy with being lubricated by mineral oil the turbo will not.

John

[TOOL]

Castrol GTX 15-W40 semi synth. End of.

Next.

[MelloYello]

Castrol GTX 15-W40 semi synth. End of.

Next.

ASDA have it on sale 4litres for £12

[TOOL]

Not bad. £14 delivered too.

[myatt1972]

Ive heard of lots of Elford engines going pop, how many turbo's give up the ghost ?
Keeping the engine happy would be my priority.

[Lucky]

Hmmmm. Undecided.

I've only ever used mineral oil in my FD, on both stock twins and plain-bearing big singles and I've never broken a turbo. Well, that's a lie, actually, I've broken two but that was from pelting them with apex seals What I should say is I've never had the bearings wear from oil problems on one. However, with Halfrauds now stopping their 10/40 mineral oil it only leaves the 5/30 easily available which is probably rather better suited to use in a lawnmower, maybe I'll just go to Castrol synth because frankly life's too short to go chasing all over the country/internet trying to find the right grade of mineral oil .

[kenwhiteside]

With regards to mineral oil in a turbo charger dont forget that the turbocharger is water cooled and also from the 80's so probably has clearances well in excess of a modern unit. I would think when running and there is a good flow of oil it would be OK. The danger with mineral oil would probably come if you did not let it cool properly before shutdown and you got laquering in the turbo bearings.

We have some guys from honeywell-garrett in this week so I will ask them.

Tim

[ian65]

With regards to mineral oil in a turbo charger dont forget that the turbocharger is water cooled

every Elford I've ever seen has had an oil cooled turbo

[spoddy]

well i use castrol magnatec 15w30 and have no problems at all.
i also use castrol 2T 2 stroke oil for scooters/bikes as a premix and have noticed, more power, better mpg and smoother performance.

that's on a renesis multi side 6-port engine. i have 93400 miles too

but i always wondered what oil to use in the older engines, i.e. the 12a and see you all recommend castrol again.

[RamoNZ]

With regards to mineral oil in a turbo charger dont forget that the turbocharger is water cooled

every Elford I've ever seen has had an oil cooled turbo

Yep, even modern turbos can be oil cooled only - my 620hp-worth-of-peak-airflow Turbonetics T62-1 is oil cooled only and plain bearing.

Heat control is mainly where it's at though, any oil combination will have a burning point - best example is butter vs oil in the fry pan - the butter will burn very easy whereas the oil will take it. So having a stupid hot engine and switching is straight off can cause the oil in the turbo bearings can turn to carbon - but that is just bad practice in general and even though fully synthetic oil will help I still wouldn't do it.

Another benefit of synthetic oil is the longevity and it's ability to keep particles from causing damage, further benefits are shear strength and cleaning properties.

So, a good quality mineral oil (castrol) that is changed regularly (can't help that if you are omp) and is kept cool(factory fitted oil cooler except s3) should be as friendly to the turbo as anything else.

One caveat though, a ball bearing turbo might prefer Synth for some of the above reasons but from what I understand BB turbos can't hack operation at the back of the rotary so no dramas there then!

Small interesting random fact - Mclaren MP4-12abc 600bhp V8 twin turbo thing uses plain bearing turbos and runs extremely high egt - high enough that the early prototypes would burn out Cats after a few short dyno runs