Having read the article on the Ferrarichat.com forum that has been linked in this thread;

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/oil-engine-750073/

I was wondering if anyone uses 0w-20 or 0w-30 grade oil in thier FD.

I'm not interested in mineral vs synthetic comments, just curious to know if anyone is using either of the grades, in particular the 0w-20 grade and what benefits, if any, it provides.

TIA

 

From this thread that previously discussed the long ferrarichat forum post:
https://www.rx7club.com/showpost.php...4&postcount=25

 

I too would also like to get some more insight into this article and its relevance to a rotary engine.

Has anyone used 0w30 Mineral oil in there cars for extended periods of time ?

 

Did you even click the link kento posted above? , seriously...

A big part in oil selection is how you intend to use your car. Personally I would never run 0w-20/30 in anything that I own, especially my rx7. Mostly because I plan on doing a lot of road racing with it once it is put back together. Is whatever gain you are hoping to see out of running a thinner oil really worth the possibility of accelerated wear on an already finnicky motor? That's the question I would be asking if I were you...

 

My concern with an oil that thin is that it would completely drain off the rotors and give you massive wear at startup.

Making that more of a problem, all of the 0W- oil weights are coming from new manufacturer specifications that require lower anti-wear additives to protect the catalytic converters. Mobil1 has in fact fully disclosed the ZDDP counts (a major sliding wear additive) in their various weights and the 0w-'s are lowest. So it pays to run oil weights that are of the era from when your engine was designed.

I've been running 20w-50 in summer and 10w-30 or 10w-40 the rest of the year. I think that's a safer place to be.

 

The RX8 guys run 5w20. I've known a few RX8 guys to try zero weights but not extensively. The lowest I would probably go would be 5w30 on a rotary. Keep in mind that the rotary has a lot of blow-by so you'll get fuel diluted into the oil. Not idea, but it is what it is.

 

That was my view till I read the article, but the main focus of the article is that all oils are much too viscous at startup and having a 'thinner' oil will reduce the warm up period and therefore minimise the wear that occurs at startup.

As far as using oil weights of the era of the car, that again seems not to be the way to go as modern oils are more stable and cause less wear, i.e. the latest spec SM oil would always be better than SH which I think is an early 90's spec.

I'm not trying to argue with anyone, but there was a lot of info in the article that certainly changed my view on oil grades.

 

The rotary relies on oil clinging to the internal parts during startup for protection. We also get oil injected directly into the motor, which helps some too. Thinner oils don't tend to do as well for this.

The debate on SM vs. SH is far from settled, true, but basically the choices for additives that oil manufacturers can use is now more restricted.

The only real learning about this takes place by doing UOAs. I'm in the process of that right now, by the end of the year I'll have compared Mobil1 10w-40, RLI Biosyn 10w-40, and probably also Idemitsu 10w-30. That way I can compare wear rates, viscosity breakdown, and fuel dilution. (each car is different w.r.t. fuel dilution). Unfortunately I only drive 5-6k / year on this car so it won't be coming soon.

Maybe next year I'll try doing 20w-50 and 0w-40 to test the grades a bit more. I'm really curious how the 0w-40 would hold up considering the rotary internals. I have a feeling though that fuel dilution was and will remain the dominating factor in oil property reduction for our cars.

Dave

 

Exactly.

I don't think there is any harm in using 0w vs 10w vs 20w.. Maybe one causes more startup wear, maybe not.. Hard to say.. The rotary is going to be rebuilt in 50k miles anyway.

It really doesn't matter all that much which oil you use IMO. They are all going to break down due to the nature of an RX7. Yes, some "cling" better. That has been a synthetic vs mineral argument for years. MAYBE the thinner oils don't cling as well, but I have also heard otherwise. Nevertheless, the addition of gasoline in the oil will overpower any of these characteristics.

Regardless of oil, I only find three things significant:

1) CHANGE IT FREQUENTLY
2) Use the correct volume of oil and check the level regularly
3) Oil Pressure under operation (may change based on ambient temps, driving style, etc)

A good measurement that changes based on viscosity is oil pressure. As long as the pressure is what is should be under operation, then the viscosity is correct. This, of course, would be the same between 0-30 and 10-30 oil. So I guess this thread should only be discussing the "cling" vs "warm up" traits.

FYI - I use 20-50 Castrol GTX.

I would not use a 0w20 oil because the oil would be too thin during operation and the oil pressure would be too low.

 

Regarding viscosity and oil pressure, point noted.

I'm doing UOAs for my own work because the RLI Biosyn is reputed to have better viscosity vs. fuel dilution compared to other oils. I'm comparing Idemitsu because the rotary guys claim it's great. Mobil1 is the baseline "premium" oil. With the UOAs I'll be able to trend fuel dilution vs. viscosity for each oil.

 

"Always be better"? Not true. Try telling that to the '50s/'60s/70's era V8 hot rod builders here in America that have suffered camshaft galling and premature cam lifter cap wear from the drastically reduced levels of ZDDP (Zinc dialkyl dithio phosphate, a "sacrificial" extreme pressure additive in motor oil) in API SM grade oils that were mandated due to fears of zinc poisoning of catalytic converters in modern cars.

I'm not trying to argue here either, but the point of my previous post is that you need to have much more info about motor oil than just an elaborate posting with reams of sophisticated-appearing viscosity charts. Simply stating that it's OK to use ultra-light viscosity multi-grade oils in any engine just because they work in other particular engines is a major stretch of the facts that borders on misinformation. Engine design, bearing clearances, oil pump volume over rpm, engine heat, bypass valve capacity...there are way too many variables here between engines to make such a generalized statement.

While I'm not doubting the advantages of lighter viscosity oils, the main reason for the move to ultra-light viscosity multi-grade oils in modern OE applications is for fuel economy. So the OEMs design the engines that spec those oils specifically for that application.

 

Until a week or so ago, I've used 10-30 since that is what my rotary mechanic suggested. I've only owned the car just a bit less than 6 months. The last oil change was the 4th my FD has had in that time. This last time I went to 10-40. I immediately noticed higher oil pressures, particularly on start-up. In theory, as I understand it, going from 10-30 to 10-40 shouldn't make a difference for cold start. So I'm a bit confused.

Another factor could be that for the last two oil changes I had used Penzoil 10-30, this time I used Castrol GTX 10-40.

What oil pressures do you get with the 20-50 and what would you consider good/safe/optimal for start-up?

Edit: Dave, I'd be really interested to see what you find out on your UOA. Keep us posted.

 

'Fuel Dilution' Yes, that indeed would make the oil requirements for an FD very specific. As a recent FD owner I didn't realise how significant this issue was although it will obviously vary from engine to engine but always more significant than in a piston engine.

Thanks for all the responses, I look forward to your findings dgeesaman.

 

Like I said my FD is a light driver. It will take all year just to compare 3 oils.

I would great to find a couple of other owners to test some oils the same way.

Right now my budget is this:
5 qts Mobil1: $22.
10 qts RLI Biosyn: $100
10 qts Idemitsu: $100
6 UOAs: $150. UOAs to be done at 1000 and 2000 miles. Depending on how much viscosity changes I may test the oil in virgin condition: another $75 for that.

The reason for the extra oil is because you just can't drain it all from the engine. I haven't tried using compressed air in the oil pedestal to drain it out, but if that doesn't pan out my plan is to drive a few miles on the new oil type and drain it into a container for later use, then do my UOA mileage on the second fill.

If anyone else is interested it would make for a really valuable body of knowledge. While I don't consider oil choice to be a very critical factor in running an FD, it's definitely one of the least understood aspects of this car.

Dave

 

here my $2.

my friend and i compared notes, and 10years ago, 80% of the bearings were good. now 10years later 80% of the bearings are bad.

i'm thinking the new oil formulations without that zddp are to blame.

on the other hand, ive been running 5w-20 for years, and it seems like its fine.

the only potential issue ive had, is the metering pump on my 79 stopped working with the thin oil, when the oil was changed back to the weight its supposed to have, then the metering pump started working again. seems to be just that one car (30 year old 90,000mile pump)

fuel dilution is an issue, on the turbo cars. my fd buddy has been checking the evap and pcv systems when hes got these cars apart, and they sometimes fail. its not obd2 so theres no cel, but it can be bad