8.1L and general viscosity discussion

[Poobank]

Hi guys,

New here and wanted to talk about oil viscosity and apply it to my 2001 yukon 2500 8.1L engine. as you know GM recommends 5w30 for about all their v8 engines around this time.

The reason for this discussion is b/c this motor is also used in marine applications and has a different oil recommendation. in addition i have noticed other car manufacturers recommend different oil viscosities in different countries, regardless of temperatures. also GM recommends a heavier wt oil 15w50 for the c7 vette if driven on track.

with this said, i have heard people run 15w40 in the 8.1L to reduce oil consumption. oil consumption is inherent for these engines. even one of the most popular engine builder/modifier for these engines recommends heavier wt oil to reduce oil consumption. i think 5w30 is not bad as i have 190k on the motor, noticed the previous owner used 10w40 from the oil change window sticker. my take away is that i'm going to run 5w40 for winter and 15w40 for summer here in georgia. This is mainly a tow vehicle but sees some family vacations and commuting.

questions/discussion
1. what do you think about using a thicker wt oil in this engine given the fact that the owners manual states 5w30 and says not to use 20w50
2. what are your thoughts on different wt oils for different counties regardless of temperature?

thanks

Links
different viscosity for different country http://mirageforum.com/forum/showthread.php/1577-Recommended-Oil-Viscosities

GM oil viscosity for racing page 256
https://www.chevrolet.com/content/dam/Ch...ual.pdf#page373

engine builder rayler posts on topic, see post 16
http://www.offshoreonly.com/forums/general-q/269112-496-reliability-2.html

engine builders website
http://www.raylarengineering.com/index.html

 

[Nick1994]

I just drove a 26' Uhaul that had this engine in it to San Diego. The oil cap on it said to use 15w40 so that's what I topped it off with.

I personally would probably use Mobil 1 HM 10w40 or Mobil 1 Turbo Diesel Truck 5w40 (approved for gasoline engines).

 

[CT8]

15w-50 is a good choice for the engine. Actually so would any Xw-40 oil.

 

[Brybo86]

Originally Posted By: Nick1994
I just drove a 26' Uhaul that had this engine in it to San Diego. The oil cap on it said to use 15w40 so that's what I topped it off with.

I personally would probably use Mobil 1 HM 10w40 or Mobil 1 Turbo Diesel Truck 5w40 (approved for gasoline engines).

you topped off the rental??

props to you!

 

[dlundblad]

Boat engines see high constant RPM's compared to a car engine.

A something w30 or 40 should be good depending on how you use the vehicle.

 

[901Memphis]

Mobil 1 0W40 European Formula is just a little thicker than a good 30 grade, I'm using it in my 5w30 application.

 

[Shannow]

It's not uncommon for a particular architecture to have different recommendations for road/marine...e.g Honda with a 20 in road engine, and 10W30 in same base engine for marine.

5W/10W/15W40 would be plenty OK depending on what you need cold temperature start wise.

Mobil1 10W30 HM hsa an HTHS in the mid 3s, so would also be a choice

 

[Chris Meutsch]

Originally Posted By: Brybo86
Originally Posted By: Nick1994
I just drove a 26' Uhaul that had this engine in it to San Diego. The oil cap on it said to use 15w40 so that's what I topped it off with.

I personally would probably use Mobil 1 HM 10w40 or Mobil 1 Turbo Diesel Truck 5w40 (approved for gasoline engines).

you topped off the rental??

props to you!


Beat me to it.
I've done it also. Why not take 3 seconds to insure yourself vs. blowing up and messing the bed?

 

[Shannow]

I've topped off rentals before when I was over there...
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3427767/Condensed_BITOG_learning

 

[Doog]

I would use a 10w30 or 10w40. All of my big block boat engines got 25w40. You won't go wrong with a 40w.

 

[Garak]

Another option, aside from a 15w-40, would be a 10w-30 HDEO. You can leave that in all year. A 15w-40 would work fine, as well, but there is no need for seasonal changes.

 

[brian_06328]

^^ x2

I started running Rotella T5 10w30 in my 460 and never looked back. I think it's the best for the job and good year round. I use the pickup for towing a 30' 5th wheel mostly

 

[Nick1994]

Originally Posted By: Brybo86
Originally Posted By: Nick1994
I just drove a 26' Uhaul that had this engine in it to San Diego. The oil cap on it said to use 15w40 so that's what I topped it off with.

I personally would probably use Mobil 1 HM 10w40 or Mobil 1 Turbo Diesel Truck 5w40 (approved for gasoline engines).

you topped off the rental??

props to you!
Lol yes I did. I was putting 400 miles on it and did not want to deal with a broken down truck. I went to O'Reilly's and bought 2 quarts (Uhaul reimbursed me) and it took both quarts to bring the oil level to halfway between the Add and Full lines.

 

[MinamiKotaro]

Delo 10w30 or 5w40 is always a winner.

 

[rrounds]

You have 190k miles on it, you live in Ga. Just how cold does it get in Ga.? I would use 15/40 and call it a day. Even if you take a drive to where it is cold, lets say -10*F the 15/40 will work just fine. Its not like you will start it up(cold) and see how fast you can hit 100 mph.

15/40 is a great oil for a lot of high mileage vehicles.

ROD

 

[bigt61]

If you're towing anything heavy - say over 8000 lbs, I'd use M1 15W-50 - that's what I did on my big block Suburban. Other than that, 5W-30 works fine.

 

[Ojustracing]

My 8.1's get 15-40 all year round and in normally one the coldest spots in country.

 

[Poobank]

Thanks for all the suggestions. My friends were saying I'm crazy to deviate from the recommended 5w30. I guess cold is relative but it usually gets gal. I usually tow in the warmer months about 6k lbs hopefully on a biweekly basis this year. Gas mileage is pathetic so I doubt it will make a difference

 

[FastLane]

My friend has a 8.1. He runs 5w30 in winter and 10w30 in summer. He has since it was new.

 

[Ojustracing]

Originally Posted By: Poobank
Thanks for all the suggestions. My friends were saying I'm crazy to deviate from the recommended 5w30. I guess cold is relative but it usually gets gal. I usually tow in the warmer months about 6k lbs hopefully on a biweekly basis this year. Gas mileage is pathetic so I doubt it will make a difference


5/30 goes through my trucks like water. 15-40 in the summer month's is 1 qt every 800 miles or so. all depends if the driver shuts the truck off during the shift or not. In Afghanistan my 8.1 suburbans would go through 2-3 qts(15-40) every 2 weeks!!!! with ambient temps in the 110+ range.