What weight oil on forced induction 5.0's

I'm running Motul 300V Chrono 10w40 which is their car formula. I posted some thoughts/results here:

https://www.mustang6g.com/forums/showthread.php?t=92145

The way I always have looked at it, the weight of oil is determined by the bearing clearances. Forced induction does not change the bearing clearances, and knowing what I know now about how tight they are, I would not go with a thicker oil.

Click to expand...

This is true assuming temperatures are within spec. Multi-grade oils (i.e. 5w20, 5w30, etc...) are designed to protect daily driven cars across a range of temperature from cold start in Alaska to warm run in Houston. However, when you push the car hard, with a power adder and especially on a race track that 5w20 is now very fluid having lost all it's viscosity and protection. This is why we used to run thin oils in the winter and thick oils in the summer, before these multi-grade oils became used in everything.

So while you're 100% right that the bearing clearances do not change, the thickness of the oil absolutely changes with forced induction. That 5w20 can act more like water than oil if you get it hot enough. The downside of going thicker is that when you're not at your hot operating temperatures the engine may get less protection.

If you assume that a normal daily driver using 5w20 has about 190F oil temperature puttering around a highway; You can see on the attached image that a 15w40 should be of a similar viscosity at 250F under heavy load. So the question is what is your actual operating oil temperature and how thick will your oil be at that temperature and will that meet your needs for lubricating your engine? Adjust as necessary.

oesman said:

I'm running Motul 300V Chrono 10w40 which is their car formula. I posted some thoughts/results here:

https://www.mustang6g.com/forums/showthread.php?t=92145

Click to expand...

good stuff

i use 5/20 in the winter.. 5/30 in the summer this winters been damn cold here so im glad i used 5/20

"So while you're 100% right that the bearing clearances do not change, the thickness of the oil absolutely changes with forced induction. That 5w20 can act more like water than oil if you get it hot enough. The downside of going thicker is that when you're not at your hot operating temperatures the engine may get less protection. "

Can you tell me how much oil temperature is affected by forced induction? I would love to see the data you have on that.

F1scamp said:

"So while you're 100% right that the bearing clearances do not change, the thickness of the oil absolutely changes with forced induction. That 5w20 can act more like water than oil if you get it hot enough. The downside of going thicker is that when you're not at your hot operating temperatures the engine may get less protection. "

Can you tell me how much oil temperature is affected by forced induction? I would love to see the data you have on that.

Click to expand...

This will depend entirely on driving conditions, climate and your setup. There isn't a chart that was made for you yet ;). Are you just driving to the store? Are you on a race track in the Houston 98F crazy humidity heat?

You can have a 1000whp car that never sees over 200F if you do only the occasional rip through a gear and just putter around town. You could also have an N/A car that you absolutely beat the piss out of on the track when its 100F outside and you'll be cooking the crap out of your oil. This is why Ford recommends installation of aftermarket oil and other fluid coolers in the Mustang manual. An FI car is going to produce a lot more heat. The more power you make the more heat you generate. The Veyron famously had 10 radiators:

- 3 heat exchangers for the air-to-liquid intercoolers.
- 3 engine radiators.
- 1 for the air conditioning system.
- 1 transmission oil radiator.
- 1 differential oil radiator.
- 1 engine oil radiator

As I said in my post you have to adjust as necessary, that's why I linked that chart. There isn't one right oil solution for everyone. There right oil solution for most people is 5w20 since it gives the best gas mileage and most people don't run their car oil over 190-200F.

oesman said:

This will depend entirely on driving conditions, climate and your setup. There isn't a chart that was made for you yet ;). Are you just driving to the store? Are you on a race track in the Houston 98F crazy humidity heat?

You can have a 1000whp car that never sees over 200F if you do only the occasional rip through a gear and just putter around town. You could also have an N/A car that you absolutely beat the piss out of on the track when its 100F outside and you'll be cooking the crap out of your oil. This is why Ford recommends installation of aftermarket oil and other fluid coolers in the Mustang manual. An FI car is going to produce a lot more heat. The more power you make the more heat you generate. The Veyron famously had 10 radiators.

As I said in my post you have to adjust as necessary, that's why I linked that chart. There isn't one right oil solution for everyone. There right oil solution for most people is 5w20 since it gives the best gas mileage and most people don't run their car oil over 190-200F.

Click to expand...

I guess that you are assuming the oil temperature is already on the high end of what the cooling system is capable of taking care of N/A, so the addition of forced induction would take it over the edge and overheat the oil? You assume this to the point of putting thicker oil in your engine, but no data? Just trying to see where you are coming up with this. My point of view is coming from a guy that lost his factory motor from a spun bearing, got a factory shortblock and found 3 rods of the new motor at the bare min. spec of clearance. No way would I run a thicker oil.

F1scamp said:

I guess that you are assuming the oil temperature is already on the high end of what the cooling system is capable of taking care of N/A, so the addition of forced induction would take it over the edge and overheat the oil? You assume this to the point of putting thicker oil in your engine, but no data? Just trying to see where you are coming up with this. My point of view is coming from a guy that lost his factory motor from a spun bearing, got a factory shortblock and found 3 rods of the new motor at the bare min. spec of clearance. No way would I run a thicker oil.

Click to expand...

My car isn't a daily. I only beat on it or take it on the track (road course). Not only will 5w20 perform poorly at temperatures of 230+ like you will have in Houston at MSR after 5 laps; You will also damage the oil. I do have data for MY CAR, in the form of using multiple labs to analyze samples of oil. I started doing this recently and will continue doing so at each change. My Mobil 1 Extended Performance 5w20 was degraded below average viscosity for a 5w20 within 1,500 miles and that was only street abuse.

Two labs for that particular sample showed 212F viscosity as 7.8cSt and 7.6cSt. Please look at my earlier chart and tell me where 5w20 should be at 212F? It's Around 9cSt. Mobil 1's data sheet says it's 8.9 out of their bottle. While 7.6-7.8 is still serviceable in a non-HD application, that's clearly not optimal performance for a fancy synthetic 5w20, because it's cooked. At 212F it's viscosity was about the same as it should be at 230F due to damage from heat, it was basically not a 5w20 oil anymore. This is called oil shearing.

EDIT: Also the base number was 3.20mg KOH/g from what should have started around 10mg KOH/g. Which means the oil lost most of it's ability to neutralize acid and prevent corrosion.

As someone who hasn't yet had to rebuild my Coyote engine I'm definitely not going to run a thinner oil that I have lab results showing as starting to fail at a small fraction of the intended change interval.

Furthermore on change intervals, the lab testing can teach you your proper interval for YOUR application. Try Oil Analyzers Inc, they sell through the Amsoil site and seem to have all their certifications, so far it's my preferred lab.

I am not debating oil gets thinner and breaks down when it gets hot. I am curious how much hotter your oil gets since going to forced induction, to the point that you decided that you needed a thicker oil.

F1scamp said:

I am not debating oil gets thinner and breaks down when it gets hot. I am curious how much hotter your oil gets since going to forced induction, to the point that you decided that you needed a thicker oil.

Click to expand...

On the street I see around 230F on the track 250F+ if its in the summer.

The point that I decided I need a thicker oil was when I performed the lab analysis I detailed earlier that showed that at my temperatures the oil had sheared to a lighter thinner oil (damaged) and was no longer providing the protection it should be.

Wow that's crazy. What temperatures were you seeing before the procharger?

F1scamp said:

Wow that's crazy. What temperatures were you seeing before the procharger?

Click to expand...

I only had one track day with it before and it was in the winter so I wasn't paying attention to be honest. I think I did about 2x 45 min runs with 45 min cool downs while bikes were on the track. I doubt it was over 230F and on the street I only puttered around back then. Car only has ~5,800 miles on it as of today.

Ultimately it's all going to be dependent not just on temperature, but also the type of oil. Some hold up better than others, they have all kinds of additives to keep viscosity. The real test is getting it checked out by labs and also to test the labs for accuracy. This is always a problem with outside labs.

One way some organizations test outside labs (when they can't do it in-house) to ensure accurate results is to send known samples. Like I dye some virgin motor oil dark and send three different samples on different days to the same companies. See who comes back with a reasonable margin of error between samples. Oil Analyzers does appear to be certified, which some other companies do not. So far they're my favorite. But it was suggested to me that this testing should be on-going on a semi-regular basis to ensure the lab is still doing a good job.

The new motor for the upcoming GT500 requires 5w50.

Oh also I forgot to mention that shearing is further accelerated by forced induction because of extra pressure from the power. The moment that shearing happens is when oil is under pressure like on the down stroke of a piston it's squeezed out of the bearing with a huge amount of force. If you have 250F oil which is already running thin due to the temperature on top of an FI engine putting out ~800 break horse power you can bet you'll shear it to a lighter grade oil very quickly by squeezing the crap out of it. You're essentially tearing the molecules that provide that viscosity and protection.

GTBOB said:

The new motor for the upcoming GT500 requires 5w50.

Click to expand...

That makes sense, Ford has recommended 5w50 several times in "track" oriented version of mustangs. In the past it's been coyote engines which have the same bearing clearances as normal models as far as I know.