I finally did it... 10W40

[Roadbastard]

Well I decided to go to a thicker oil. After rebuilding the engine I want the additional protection of thicker oil since it's not exactly to factory spec anymore. I never liked 5W30 or using thin oils like that. Thought about going 10W30 but why bother with such a minimal difference. Went in for the 10W40 and we'll see how this goes. I've always used thicker weight motor oils just makes me sleep better at night. I've come to realize that choosing your oil should depend on your location and driving habits. I've had cars that probably never would have lasted if I used the factory spec stuff. It breaks my heart to say this but I'm leaving the 5W30 family. I just hope you guys can understand and learn to forgive me in the long run. Farewell my 5W30 friends.

[1988GTU]

Thick oil shouldn't be determined by the operator as its more so what is required by the engine. Keep in mind that higher RPM and low operating temps wouldn't be ideally safe with thicker weight oil.

[robertisaar]

so, your engine is receiving what benefit from running a thicker oil? why not just run gear oil or SAE 50 if thicker is better, or let an oil change go 20K miles too long, that way you have tar under the valve covers?

conventional wisdom is that most engine wear occurs during a cold startup, which is when the oil is at its thickest. this statement is made for the average vehicle, so exceptions will occur.

if you beat the hell out of it on the track, you might benefit from a thicker oil. at full temp and load, is the recommended oil causing additional wear that a thicker oil would prevent? you would need to do a couple of UOAs with each oil under identical conditions to find out. the thicker oil could actually cause more wear in those conditions.

[pocket-rocket]

[threadjack]

That pic is so full of win!

[/threadjack]


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[caffeine]

I know lots of guys who run thicker oils in high mileage engines. I've done it too like in my old Jetta I had with 350,000 kms and my Mitsubishi Mighty Max at about 550,000 kms. I used Rotella 15w40 in both of those.

[robertisaar]

an old engine is one thing..... this is on a fresh rebuild from the sounds of it.

[1988GTU]

an old engine is one thing..... this is on a fresh rebuild from the sounds of it.

x2

[Superdave]

I ran thick oil in my 3500 (Royal Purple 15W40) but it was a track car for the most part, 20-30 hot laps revving past 7K on hot summer days.

On a street car, run what's supposed to be in it which IIRC is 5W30.

[Roadbastard]

Well I'm back. Been working the car in a lot. The engine has really taken well to using 10W40. If you haven't been following my post this is on a rebuilt motor broken in with 5W30. So far the only standout aspect of going with the heavier weight is the motor is slightly less agile than it would be if it had thinner oil. This is a con if you want the extra pep but it's a pro if you'd rather trade for the protection. Every thick oil behaves like that till it wears in a bit more but whatever. The engine is also very quiet. It was quiet before but the valves really sound soft now. This is what I enjoy the most. The 3.1 is noisy as it is but it's nice to hear it muted. What I also noticed is that my engines vacuum improved a lot. Usually it would have some kind of reaction when you pulled the cap off like most engines do but now it doesn't even wink. I just don't see a reason to avoid thicker oil or use it. It's just there if you want it or not but your motor can take it. It's not like jumping from Dyno to Synth.

The factory oil is just the oil that's most readily available for the motor. The engineers know what it is so they stick with it to save R&D costs when designing these engines. It just wouldn't be cost effective to build an engine that couldn't run on 5W30. Think about it... What GM car doesn't use 5W30 out the factory? and what dealer doesn't have tons of the stuff in supply. I think it was even weird to see 10W30 from the factory since they used 5W30 for so long. I remember when I would have to call around to get an oil change when I couldn't do it myself and they dealers seemed baffled other weight oils existed "What? We don't carry that!". Anyway the thing is about these old GM motors is that they're simple push rod motors (and I don't care how many intake variations they make) They're pretty basic engines and that's why I like them. They don't have all the dodads and gizamajigs like Imports do so they're oiling system is pretty simple. If I was driving a honda with a mecha turbo B16AC/BC motor with dual cams and V-TEChnia engine components I'd be wary about changing form my factory oils... but this is a GM baby...it can take anything you throw at it... except for coolant gaskets. Although I'm joking mostly I've never heard of anyone having issues with running thicker oils unless they lived in some crazy frozen climate like Alaska.

[Guest]

I've come to realize that choosing your oil should depend on your location and driving habits. I've had cars that probably never would have lasted if I used the factory spec stuff.

OH MY GOD! is there another, really? Another person who realizes that lubrication choice is not just what the manual suggests, but should be based on actual vehicle use and location (environment reasons)?!


I too use a thicker oil than other people, and they would scoff at me if they knew. Granted I don't currently have a car equipped with a 660, but I do have a turbo 2.8L, and I use Royal Purple 15W-40 in it, which I find much better than the 10W-30 I have ran in it, especially at hot idle.

[caffeine]

I've heard elsewhere that Royal purple 15w40 is one of the best oils readily available. And I've also heard that turbos love diesel oil.