[SammYyYyY]

Hey all! Recently I swapped out my Mobil 1 ESP 0W-40 Dexos 2 for Mobil 1 FS 15W-50 for a track day I recently partook in; everything went great, car performed like a champ on track with zero hiccups.

I was wondering if anyone could provide some insight as to why the 15W-50 weight oil is only recommended for track use and not for street use; reason I ask is that it is a LOT cheaper than the 0W-40 Dexos 2 stuff, and I was wondering if (assuming proper warmup/cooldown procedures) there is any reason that I could not use 15W-50 on the street?

It should be noted that I would be running this oil ONLY during Utah summers (average temperatures in the low 90s to low triple digits). During the winter I would go back to a more suitable weight such as 0W-40 (even though my car is garaged during the winter and only sees the occasional cold-start/idle to maintain the integrity of rubber gaskets).

Not only is it cheaper and more readily available, my oil pressure appears to be slightly higher which I like (31-32 PSI at warm idle as opposed to 29-30 PSI).

Warranty is out of the question as my powertrain warranty recently expired. Also, if it makes a difference, my oil pump failed before my warranty expired (as did many 2018s) and was replaced under warranty by GM; I believe that the newer pumps they are throwing into these cars are stronger than the ones they left the factory with.

If anybody could provide some insight that would be fantastic. Thanks!

[Smokin19]

In my 19' manual it states if Mobil1 0-40 with dexos is not available Mobil 1 5-30 with dexos is acceptable for street use. I have been running this weight for over 3 years now and only on the street, I don't track the car.

[Rock-It Man]

Do you really need to pinch pennies buying the right oil? Are you smarter than GM engineers?

[SoCal Smith]

Originally Posted by SammYyYyY

Hey all! Recently I swapped out my Mobil 1 ESP 0W-40 Dexos 2 for Mobil 1 FS 15W-50 for a track day I recently partook in; everything went great, car performed like a champ on track with zero hiccups.

I was wondering if anyone could provide some insight as to why the 15W-50 weight oil is only recommended for track use and not for street use; reason I ask is that it is a LOT cheaper than the 0W-40 Dexos 2 stuff, and I was wondering if (assuming proper warmup/cooldown procedures) there is any reason that I could not use 15W-50 on the street?

It should be noted that I would be running this oil ONLY during Utah summers (average temperatures in the low 90s to low triple digits). During the winter I would go back to a more suitable weight such as 0W-40 (even though my car is garaged during the winter and only sees the occasional cold-start/idle to maintain the integrity of rubber gaskets).

Not only is it cheaper and more readily available, my oil pressure appears to be slightly higher which I like (31-32 PSI at warm idle as opposed to 29-30 PSI).

Warranty is out of the question as my powertrain warranty recently expired. Also, if it makes a difference, my oil pump failed before my warranty expired (as did many 2018s) and was replaced under warranty by GM; I believe that the newer pumps they are throwing into these cars are stronger than the ones they left the factory with.

If anybody could provide some insight that would be fantastic. Thanks!

I didn't drive my car a lot when I was between track days and kept the 15w-50 in it. I warmed it up and drove it normally on the street to the local car show. i think GM moved to the 0-40 for EPA/fuel economy probably for "daily" usage.

I did read somewhere that the heavier-weight oil could burn out the cats faster but idk if that was true or not. (didn't have them anyways)

[SammYyYyY]

Originally Posted by Rock-It Man

Do you really need to pinch pennies buying the right oil? Are you smarter than GM engineers?

Not necessarily about pinching pennies, 15W-50 is more readily available, and is categorically better for track use; I drive my car hard on the street too, so knowing that there is extra viscosity for bearing protection would be nice so long as I’m not committing any other damage.

Also, GM engineers are the same people that designed a faulty oil pump and a wet sump oiling system in a literal track car; the mere notion that I have to switch to 15W-50 weight oil for track days IS stupid, so maybe watch your tone next time you decide to turn a blind eye to some of their stupidity

[SammYyYyY]

Originally Posted by SoCal Smith

I didn't drive my car a lot when I was between track days and kept the 15w-50 in it. I warmed it up and drove it normally on the street to the local car show. i think GM moved to the 0-40 for EPA/fuel economy probably for "daily" usage.

I did read somewhere that the heavier-weight oil could burn out the cats faster but idk if that was true or not. (didn't have them anyways)

I did read about the cat-situation. I am stock right now, but am planning to go with ARH high-flow longtubes in the future (unfortunately I can’t go catless as emissions tests here in SLC are somewhat stringent).

[SammYyYyY]

Originally Posted by Smokin19

In my 19' manual it states if Mobil1 0-40 with dexos is not available Mobil 1 5-30 with dexos is acceptable for street use. I have been running this weight for over 3 years now and only on the street, I don't track the car.

Yeah, when I first got the car I did run 5W-30 as that was the factory fill; I’ve since opted against it as my local performance shop I maintain my car with has advised against it. I also drive my car pretty hard on the street (we have some awesome, empty, technical roads here in UT that I take advantage of when it is safe of course), so the extra weight of 0W-40 is nice for peace of mind on the street

[SoCal Smith]

Originally Posted by SammYyYyY

I did read about the cat-situation. I am stock right now, but am planning to go with ARH high-flow longtubes in the future (unfortunately I can’t go catless as emissions tests here in SLC are somewhat stringent).

California has some difficult smog, but I was running ARH catless long tubes! (I have a set for sale lmk!)

[CasualGuy]

Originally Posted by SoCal Smith

I didn't drive my car a lot when I was between track days and kept the 15w-50 in it. I warmed it up and drove it normally on the street to the local car show. i think GM moved to the 0-40 for EPA/fuel economy probably for "daily" usage.

I did read somewhere that the heavier-weight oil could burn out the cats faster but idk if that was true or not. (didn't have them anyways)

👆This. I and others I know who tend to log more track miles than street miles in the ZLE run 15W-50 all the time because it's a hassle to change back and forth between events. Since the 15W-50 is a thicker oil, on cold starts it's important to take it easy with your right foot for the first 5 minutes or so of driving until the oil comes up to temp, and this is even more important in cooler weather.

That being said, be warned that you will most likely burn out your cats doing this. Literally all but one of the ZLE guys I run with have blown out cats on track, which turns out to not really be a big deal (smog/emissions issues excepted).

Both times it's happened to me (coming out of turns on track), the car shot a cloud of cat guts out the tailpipe, threw a CEL and Service StabiliTrak message, and went into a sort of limp mode. After returning to the pits, shutting down, then restarting, the codes self-cleared and I was able to get back on track right away. There's a little more stuff shooting out the exhaust for the next half-lap or so as whatever catalyst remains is ejected, but then the only differences you'll notice are a more aggressive exhaust sound and a stronger exhaust smell. As a matter of fact, just after I recently had both cats replaced under warranty, my wife commented, "Your car doesn't sound as good anymore." Yeah, she's a keeper.

[SFV1LE]

Originally Posted by SammYyYyY

Not necessarily about pinching pennies, 15W-50 is more readily available, and is categorically better for track use; I drive my car hard on the street too, so knowing that there is extra viscosity for bearing protection would be nice so long as I’m not committing any other damage.

Also, GM engineers are the same people that designed a faulty oil pump and a wet sump oiling system in a literal track car; the mere notion that I have to switch to 15W-50 weight oil for track days IS stupid, so maybe watch your tone next time you decide to turn a blind eye to some of their stupidity

The state of the art dry sump C8 Z06 runs M1 5w-50. M1 true racing oil is 0w-50. If you run any high performance car on track hard up to super high temps you are always better switching to a 50 weight oil, this is not stupid. In my opinion it's stupid to run a non-1LE ZL1 on track with 0w40.

And btw, know of any ZL1 1LE engine failures on track from oil starvation due to the wet-sump? I have not heard of any reported. But I do know of several dry-sump C7 failures from oil starvation among fellow drivers here at my tracks in CA.

I run M1 15w50 year round because I do minimal driving between track days and it's never that cold in CA, but I wouldn't recommend 15w50 in below freezing weather in UT unless you're starting car in a heated garage and let it warm up--then you'd be fine. And M1 5w50 would be fine.

[Rock-It Man]

I wouldn't use an oil with a 15W lower limit in a daily driving situation. You want a lower viscosity for frequent startups.

[SFV1LE]

Originally Posted by Rock-It Man

I wouldn't use an oil with a 15W lower limit in a daily driving situation. You want a lower viscosity for frequent startups.

Here's some good news for ZL1 people who want to run 50 weight oil for track and not worry about switching to lower weight between track events and also don't want to be starting on a 15w in colder temps...

Mobil Supercar 5w50 Supercar - DEXOS 2 Approved:

https://www.amazon.com/Mobil-5W-50-S.../dp/B0BWPLYYTT

This new M1 5w50 Dexos 2 Supercar seems like it was produced by GM/Mobil specifically for the C8 Z06 application, hopefully the price will come down, but still cheaper than frequent oil changes. Looks like this still is not ok for ZL1 1LE on track from a warranty perspective, where GM requires the 15w50 and can void warranty if your motor blows and they do oil analysis. But it should protect as well or better than the 15w, I hope they approve this for ZLE ppl.

[SammYyYyY]

Originally Posted by SFV1LE

The state of the art dry sump C8 Z06 runs M1 5w-50. M1 true racing oil is 0w-50. If you run any high performance car on track hard up to super high temps you are always better switching to a 50 weight oil, this is not stupid. In my opinion it's stupid to run a non-1LE ZL1 on track with 0w40.

And btw, know of any ZL1 1LE engine failures on track from oil starvation due to the wet-sump? I have not heard of any reported. But I do know of several dry-sump C7 failures from oil starvation among fellow drivers here at my tracks in CA.

I run M1 15w50 year round because I do minimal driving between track days and it's never that cold in CA, but I wouldn't recommend 15w50 in below freezing weather in UT unless you're starting car in a heated garage and let it warm up--then you'd be fine. And M1 5w50 would be fine.

Valid points dude! I wasn’t aware of the C7 dry sump oil starvation failures on track or the use of 5W-50 in the C8Z.

I was mostly basing the 0W-40 dry sump > ZLE wet sump situation based off of C7 Z06 motors allegedly being safe to run on track with 0W-40 weight oil even on Z07 stage 3 aero cars, and stuff like Porsche GT cars being the same, ofc.

[SammYyYyY]

Originally Posted by SFV1LE

Here's some good news for ZL1 people who want to run 50 weight oil for track and not worry about switching to lower weight between track events and also don't want to be starting on a 15w in colder temps...

Mobil Supercar 5w50 Supercar - DEXOS 2 Approved:

https://www.amazon.com/Mobil-5W-50-S.../dp/B0BWPLYYTT

This new M1 5w50 Dexos 2 Supercar seems like it was produced by GM/Mobil specifically for the C8 Z06 application, hopefully the price will come down, but still cheaper than frequent oil changes. Looks like this still is not ok for ZL1 1LE on track from a warranty perspective, where GM requires the 15w50 and can void warranty if your motor blows and they do oil analysis. But it should protect as well or better than the 15w, I hope they approve this for ZLE ppl.

This is fantastic news, and seems well worth the money to me assuming warranty is not a factor (I’m out of warranty anyway, so there’s that.)

Since this is Dexos approved, it should alleviate the worries about burning up the cats too?