What engine oil?

[hmclaughlin67]

Isn't a 10w oil only thicker than a 5w oil when it's cold?

The second number is the actual oil weight at running temp (10w-30, 10w-40, etc). So a 10w-30 oil will only be thicker than a 5w-30 oil when it's cold.

Yes that’s correct. Has anyone here been in the same situation and just switched to a thicker oil without complications long-term?

 

[hmclaughlin67]

Yes that’s correct. Has anyone here been in the same situation and just switched to a thicker oil without complications long-term?

I’m thinking a 5w-40 rather than you no to a 10x-30. I live in PA so it gets cold up here and I don’t want rough starts either. Any input at all would be great.

 

[hmclaughlin67]

I have a 2005 Yukon XL with the 5.3. I have an oil leak problem, after 24 hours of sitting it will leave 2 small puddles of oil about 1.5 inch across, and one about 4 inches across. I added AT-205 to my oil a few weeks ago, and it completely resealed them and I lost no oil at all. I noticed that the puddles have returned tho, slowly at first but now they’re back to the same size. Anyways, I was wondering what brand of oil do you guys recommend? I’ve heard great things about both Mobil 1 full synthetic high mileage, but also valvoline full synthetic with the max life. My current plan is to do the oil change this weekend as it’s already needed, and then replace 8oz of oil with the AT205 to help seal up again. Also, any inquiries on the Bar’s stop leak specifically for the rear main seal? I’ve heard good things about it as well, and was wondering all of your opinions. Also was a little concerned it might be too much sealant additives at once. Thank you!

Edit: The vehicle has 203k miles and I go between 3-5k between oil changes.

Hopefully the final update. Today I did an oil change, and in 4k miles my full synthetic oil was fairly dark and had dirt throughout. This isn’t surprising tho as a week ago I noticed my air restrictor was missing and was allowing dirty air to go straight through the intake. That’s duct taped off for now while I wait for the replacement, but overall the oil was as expected. I put in 6 quarts of Mobil 1 full synthetic high mileage extended performance (what a ******* mouthful). I used Mobil 1 oil filter as well and added in 8oz of ATP AT-205. If you don’t hear from me again, it means the oil leak has stopped and everything is going smoothly. I always try to post final updates on these because I know the frustration of trying to find answers to a problem and no one ever posted a final update to these threads on if it worked or not lol.

 

[EddieC]

I have had more than one occasion where switching from conventional to synthetic oil on older vehicles caused almost immediate leaks. Those were vehicles that never saw synthetic oil before though and were not spec'd to use it. I followed the popular claims that people used synthetic oil in those particular vehicles without issue but that wasn't my experience.
I was lucky because switching back as soon as I saw the issues resolved the leaking. I still have them and they are tight and dry on conventional oil.

I'm just sharing my experiences and not advocating going against any manufacturer's recommendations to the contrary.

I would not be comfortable using any oil additives not having seen tests of how those things make it through the bearings, oil galleries, lifters,etc. I know in the old days sludge causing goops were used in dying engines and I've seen the result of that. An old girlfriend's father did that in his Ford Fairlane and I saw the 3/8" thick layer of buildup inside the valve covers when I had the misfortune of inheriting the car and got to burden of taking it to the junk yard. I was convinced that it used more oil than gas.

 

[RST Dana]

We used to run straight 50w Kendall in our BB Chevys in se TN without any issues all year long. Winter starts took a free minutes to get the soup to the best temps sometimes.

 

[D -money]

I have a 2005 Yukon XL with the 5.3. I have an oil leak problem, after 24 hours of sitting it will leave 2 small puddles of oil about 1.5 inch across, and one about 4 inches across. I added AT-205 to my oil a few weeks ago, and it completely resealed them and I lost no oil at all. I noticed that the puddles have returned tho, slowly at first but now they’re back to the same size. Anyways, I was wondering what brand of oil do you guys recommend? I’ve heard great things about both Mobil 1 full synthetic high mileage, but also valvoline full synthetic with the max life. My current plan is to do the oil change this weekend as it’s already needed, and then replace 8oz of oil with the AT205 to help seal up again. Also, any inquiries on the Bar’s stop leak specifically for the rear main seal? I’ve heard good things about it as well, and was wondering all of your opinions. Also was a little concerned it might be too much sealant additives at once. Thank you!

Edit: The vehicle has 203k miles and I go between 3-5k between oil changes.

I've never heard of so many Band-Aid answers to an obvious mechanical issue. SEALS leak for a reason.duh.

 

[EddieC]

I've never heard of so many Band-Aid answers to an obvious mechanical issue. SEALS leak for a reason.duh.

And here I had assumed that Chevy solved rear main bearing seal issues of the 60's.
Hope mine holds up because I hate oil leaks. Contrary to popular rumors, my old Triumph has never been a leaker.

 

[OR VietVet]

And here I had assumed that Chevy solved rear main bearing seal issues of the 60's.
Hope mine holds up because I hate oil leaks. Contrary to popular rumors, my old Triumph was not been a leaker.

My old Harley Knuckle Head was. Come to think of it, so was my Pan Head.

 

[89Suburban]

I think @iamdub runs 15W40 exclusively in his.

 

[cmhorns]

I have a 2005 Yukon XL with the 5.3. I have an oil leak problem, after 24 hours of sitting it will leave 2 small puddles of oil about 1.5 inch across, and one about 4 inches across. I added AT-205 to my oil a few weeks ago, and it completely resealed them and I lost no oil at all. I noticed that the puddles have returned tho, slowly at first but now they’re back to the same size. Anyways, I was wondering what brand of oil do you guys recommend? I’ve heard great things about both Mobil 1 full synthetic high mileage, but also valvoline full synthetic with the max life. My current plan is to do the oil change this weekend as it’s already needed, and then replace 8oz of oil with the AT205 to help seal up again. Also, any inquiries on the Bar’s stop leak specifically for the rear main seal? I’ve heard good things about it as well, and was wondering all of your opinions. Also was a little concerned it might be too much sealant additives at once. Thank you!

Edit: The vehicle has 203k miles and I go between 3-5k between oil changes.

YOU NUMBER 1 CHOICE HANDS DOWN IS: Fix your oil leak FIRST! Do not overlook this at all as it will be the death of your engine, for many reasons. As far as oils: Mobil 1 Full synthetic is #1 and if you can't find it, Castrol Full Synthetic as a second choice, which is very good oil. (don't fall for the high mileage stuff in ANY brand). I've torn down motors due to unrelated issues and engines that I've ran with only these oils, it's an amazing difference than what I've seen in in other engines that have ran just cheap oils! Do yourself a favor and block out what you hear if someone gives you negative feedback on these 2 brands! On the other hand, if you going to ignore your oil leak, simply go with the absolute cheapest brand name oil you can buy and change it often, which is not what I would suggest, but if you ignore your oil leak, 1. your just pouring it out on the ground anyway, and 2. that motor won't last anyway, so save your money for your next engine or vehicle purchase! Good Luck!