I am sure this has been answered before, but I cant find it by searching.

This is the first oil change after SakeBomb rebuilt the engine.
Its about 380hp to the wheels, single turbo conversion.

We live in Reno, NV and it gets cold here.

What oil viscosity would be best for a winter environment?
We are thinking 5W-30 Synthetic Mobile 1.

 

I did some more searching,
seems a number of folks use Castrol GTX 10W30 (non synthetic) for winter driving

 

Questions like this are for your engine builder. Everyone has their opinion on stuff like this but are not the ones that are in a position to honor a warranty should something go wrong. Do what your engine builder says to do.

 

FOR WINTER:
If your car has dual oil coolers, stuff a towel into the inlet duct for the second oil cooler. This is to stop air flow through it.
If you don't, the engine oil will run too cold for winter.

YEAR ROUND
If you can(safe parking), upon returning from a good drive, remove the oil filler cap and slightly pull the oil dipstick out by about three inches.
Do for about 30 minutes.
This allows the oil pan to breath out gasoline and combustion vapors.
If you park in a garage, you will smell what I am talking about. Leave the door open for ventilation.

 

^Interesting, never thought to do this. Has this measurably reduced your fuel/oil dilution over time? I think all of us change our oil on crazy short intervals mostly because of fuel/oil dilution - if we could extend those change intervals a little bit based on hard data that would be great

The only real way I know of to test for this would be to send dipstick oil samples to a lab, noting the miles or hours of run time on each sample. You would start the testing after a fresh oil change, so your first sample would be @ 0 miles/fresh clean oil, and the last sample taken just before the next oil change at whatever miles it was. You would also need to do this sampling test over at least 2 oil change cycles - one cycle without doing the cap removal trick, to baseline what your "normal" fuel/oil dilution is, and then a cycle or two after where you do the cap trick to see if it results in any measurable difference in fuel/oil dilution.

 

This would be a cool thing to do, you can send samples to blackstone for a full analyzation. This would have to be somebody that drives their car a lot thought in order to get quick results. It would probably take me a couple years even I we checked at 2000 miles unless I was able to make it to a DGRR event or something.

 

Yeah, I'd have a tough time racking up sufficient miles too, outside of the annual DGRR trip. I typically end up changing the oil on my rotaries by calendar date rather than miles. With an FC & FD, only one of them gets to go to DGRR each year, so for the one that does go, it gets an oil change before DGRR and then another one right after DGRR. For the rotary that doesn't go to DGRR, it gets the one oil change/year just before DGRR and it maybe racks up a few hundred miles before the next oil change.

Now that I think about cewrx7r1's suggestion to remove the filler cap after a drive, I think that for those of us running open air vented catch can setups instead of the OEM closed PVC system, it's not going to make a substantial difference in how much fuel remains diluted in the oil. That's because the sump is already always vented to atmosphere. Removing that cap after a drive might speed up the fuel vapor evaporation process a bit, but I don't think it would effect how much fuel remains diluted in the oil in the end. But the cap removal trick probably would make a difference if you're running the OEM closed PVC system.

 

if you're getting that "lung butter" then taking the cap off after a run does help.

 

I think your theory regarding those of us using a catch can setup is correct. Note: I have no engineering/scientific reason for saying this...just anecdotal:
Every year there is a big car event here in Pgh, The Vintage Grand Prix. There is a very big car show associated with it. The amount of cars that attend means there is about a half hour of VERY slow moving/idling while everyone cues up to enter the event. The first year I took the FD, as soon as I parked, I noticed a SIGNIFICANT fuel smell as soon as I popped the hood after parking. So much so that I actually was crawling around looking for a fuel leak. I couldn't find one, so I just assumed it was one of the other cars around me. But after reading this theory, I'm thinking that may have been exactly what I was smelling.

 

Thinking about this a little bit more in very humid climates such as mine, I think popping off the oil cap until cool down may be a bad idea. Leaving the cap open would probably draw in more than usual humidity during cool down exposing the internal portions of the engine to higher than usual humidity (the crankcase is not air tight by any means.) Condensation in the crankcase is already pretty high and I don't think I would want to introduce more if I don't need to. I first noticed this when I moved from Colorado to Florida. In Colorado, after a whole day of running the wife's car hard, I would have just a little bit of water in the catch can (poor placement on my part due to lack of space and products available at the time) but when we moved to Florida, I would literally have to drain the water out of the can halfway through the day during an autox event just because of the rise in humidity. I noticed this on my FD at the time as well. I would get the milkshake on the oil cap in Florida while in Colorado it was non-existant. My argument may be moot because I have no real way of measuring actual water levels in the crankcase at any given time other than the examples I just mentioned. I think I would rather just chance my oil every 3000 miles or one year which ever I reach first.

 

Just a nerdy point of discussion:
Nothing is going to condense inside the engine due to high humidity in the outside air. The "dew point" is the ambient temperature below which condensation will form. That point cannot be higher than the actual ambient temperature.
The fact is, everything in the engine compartment is much warmer than that if the engine has run for more than a few minutes. So the condensation you are seeing is the result of moisture inside the engine which forms as a result of combustion.

Moisture on an exposed surface will evaporate slower if the dew point is higher, but when the surface is warmer than the ambient, moisture will always evaporate, not condense.

 

I'm going to have to disagree with that. We reach dew points almost daily here. You mentioned that everything in the engine compartment is much warmer (yes if you are running the engine) but eventually it is going to cool down (like when you park over night.) When I step outside every morning, my grass is wet like it rained (but it didn't rain), if you touch the side of my house or a window, its wet, the entire outside of my cars that are parked outside are wet etc. If you pop the hood to my car that sat outside overnight, everything in the engine bay will be wet. That's just the nature of living in a humid climate and something that was totally foreign to me until I moved here because Colorado is a super dry state. If the grass is wet, it rained or you watered. The only condensation you saw may have been with super cold drinks sitting outside building a little moisture on the outside. If you do the same here, you will literally have a puddle.

So from my personal experience, I can definitely see a chance of condensation building up inside my engine just like it does on the outside (intake manifold, rotor housings, water pump etc.) if the humidity level is the same inside the crankcase as it is outside from leaving the oil cap off. I also understand about the condensation being part of the combustion process (I was a mechanical engineering and physics major along with building cars pretty much my entire life) but the fact still stands that in a more humid climate, I had at least 10 times more water in my catch can in one climate vs the other. Same car, no changes other than location. This did not come from watered down Florida fuel.

 

Of course stuff gets wet left outside.

We were talking about a lot of moisture in a catch can or under the filler cap after running, so the engine is hot.

I never would leave the oil fill cover off overnight, especially outside, so that's a scenario I didn't consider. Around here there are all sorts of critters roaming around overnight, and even though the car is garaged, I would not trust that one would not fall in there by accident.

I've never had a mouse nest in my FD, but I've had them in other cars, even in a garage or a trailer with no obvious points of entry.

 

Oh man, I saw some stuff when I was working at the Ford dealership. Lots of Mice damage to Harnesses and even a 6 foot python. I worked for Nissan for much longer and didn't see nearly as much crazy stuff as I did with Ford for some reason. Had to have just been a coincidence.

I don't think I would feel ok just pulling my oil cap off and leaving for half an hour honestly. I would have to make some kind of screen cover for peace of mind and add a sticky note to the steering wheel or something to remind me that I pulled it because I can very easily get distracted in a half an hour and totally forget.

 

You could DEFINITELY overthink it, but you could also just fill 'er up with some 10W/30 in the winter or some 20W/50 in the summer, then go for a drive.
Castrol GTX always and forever.

 

The worst experience I've ever had with condensation is when we towed my FVee to Daytona in January 1971, IIRC, for speed weeks . The roads down were snow, ice , and salt-covered. When we went out to start the V8 Nova we towed with in the morning it wouldn't start because all the salt on the engine, especially the plug wires, attracted moisture (we were near the ocean). There were sparks everywhere except where they needed to be at the plug gap. It was really hard to get it to start, but luckily we had AAA coverage and the mechanic jumped it for us after we dried it out a bit until it started.

 

My FD has a single turbo and I do not recirculate crankcases gases back into the turbo.
Both of the original oil pedestal hoses go into my 1 quart blow-by tank which then allows any non condensed gases to escape to atmosphere under the car.
This tank has a valve and drain hose so I can drain it periodically.

Even with this setup, there is still gasoline etc, fumes in the crankcase after driving. Thus I allow them to escape after parking the car at home as I mentioned.

About the oil cooler block off. A few years ago I was wondering about winter oil temps. After placing thermo strips on top of the oil filter and engine front cover where the oil leaves he engine, it showed the oil at about 140F in the filer.
The second oil cooler acts like a large heat sink even when its bypass valve working and thus still cools the oil more.

I have posted this before.

 

We do have dual oil coolers, will block one of them off.
Are the "gasoline and combustion vapors" the reason there always seems to be the smell of gas around the car?
We have a catch can that vents to the air, but that doesn't seem to give off gasoline vapors.

 

Some fuel dilution over time is pretty common… maybe universal, on rotaries. One of the reasons oil change intervals should be shorter than what many are used to. It’s aggravated by a lot of cold starting and idling, especially in cold weather. I think it’s caused by a lot of things that would be fun to talk about in a dedicated thread. But in any case it’s probably most noticed on the stock ecu.

As for covering one of the two coolers, there is a thermostat in that system.


I don’t intend this as smarmy, but imo the best thing you can do for an FD in the winter is leave it parked and buy a beater Honda or Toyota. The car is expensive to fully insure, expensive to repair, low-slung and probably on summer tires. It’s also rwd, sucks on slick roads with little trunk space and gets terrible mileage.
An old fwd beater with a decent heater and all-seasons on the other hand…

 

Sorry but you missed the point on the thermostat and oil cooler acting as a giant heat sink even when it is bypassing the oil.
This also has been mentioned a few times in the past.

 

Sorry you missed the point. Not sure I’d personally want do that unless I was monitoring oil temps but OK…taking your word for it. I never investigated winter conditions because I don’t care.