10w-30 is not a popular grade in my country so I can't find any and it's freezing winter so I don't think 20w-50 is right atm.

The only 10w-30 I found is designed for heavy vehicles and trucks and diesel engines but says can be used in Ford light commercial vehicles as well.
http://www.shell.com/static/tu-tr/do...X%2010W-30.pdf

The closest viscosity I can get is 10w-40 but I read in previous oil discussion threads that it leaves more ash/residue and causes carbon deposit.
http://www.shell.com/static/tu-tr/do...s%2010W-40.pdf

Other options are 5w-30, 15w-40 and 5w-40.

Which viscosity should I buy for winter?

 

After calling many shops I found a 10w-30. It's called Elf Victory FE but it's for turbocharged diesel engines and semi-synthetic. Is this going to be OK?

I am thinking diesel = heat, high torque, so it can't be bad for a rotary engine but im not sure

 

5w-30 should be fine.

 

Yeah 5w-30 is available in Mobil Super FE Semi-Synth. and 10w-40 is available in many brands. Just read diesel oil has detergency properties which can be good for engines with carbon buildup.

 

I wouldn't use mineral oil in winter. I'd use the 5w-30, 10w-40, or 5w-40 synthetic.

David

 

Synthetic = ash residue / carbon build up regardless of the season. Not all synthetics but I don't know have time to trial and error.

5w-30 is what I'll probably be going with or will be the test mule and try 10w-30 diesel oil with high detergancy properties.

From what I've read 10w-40 burns worse then 10w-30, leaves more residue due to the additives inside, just like synthetics, not all 10w-40 oils are the same but again I don't have time to experiment.

I'll go mineral or semi-synthetic, change my oil regularly every 2.5k miles, save $$$........ Synthetics might be better on cold start-up or under track conditions but I think for street use mineral will be fine.

Btw on my other cars I use nothing but synthetic where oil change intervals are longer etc.

 

I've heard an incredible variety of opinions on synthetic and clean burn. I use it and I know engine builders who endorse it. Of course it will vary depending on the brand and grade of synthetic and combustion chamber temperatures, but it's not related to the synthetic hydrocarbons themselves. In fact Idemitsu makes a rotary specific oil that is synthetic base with a strong following. But I don't intend to change your opinion on that because I happen to think both mineral and synthetic can do the job very well.

You might want to post this question to the Aussies or European section as the brands of oils you're describing are specific to those regions.

David

 

Don't get me wrong I'm all for synthetic in general but the arguments against synth oils I've read in this forum all make sense. Times have changed and oils in general have come a long way it's just that I don't have time to test a synthetic oil and even if I did, I'd only know the result after opening the engine plus there are too many variables to narrow the findings down to the type of oil.

Considering all this mineral seems to be the true and tested oil here. Idemitsu synth rotary oil seems to be popular too but also proof that something ha to be done to a synth oil to make it a rotary oil and maybe its not only the cleaner burning function cause other manufacturers with clean burning synth oils wouldnt mind adding the word rotary on their bottles for extra sales if it was that simple.

Anyway im changing the oil tomorrow as well as the clunky bushings. I will buy either 5-30ss or 10-40ss (semi synth). I just need to read more about 10-40 in the forum cause I know plenty ppl here use it.