Is 5w-30 oil and no thermostat a big no no in winter?

[AntiqueAtHeart]

Ive been driving my '66 long bed fleetside for about a year now. Ran it with 10w-30 and no thermostat in the summer and the temp never topped 200*. Now that its ~40* to 50* outside just about everyday, I switched to Mobil Super 5w-30 conventional oil and still have no thermostat due to lack of time to put one in. I've been driving everyday for about a month this way with an average of about 10 miles a day. The oil currently has 1700 miles on it and the engine is a 350 chevy with a Comp Cam 292 and stock valvetrain except springs and pushrods. I've put almost 4000 miles on it since rebuild.

It has now started to rattle badly like loose valvetrain and is missing on one cylinder. I'm pointing to the valvetrain......bad lifter.....

Did I kill my engine with thin conventional oil and no thermostat in winter?

I sure hope not. I'm going to try to pull it apart tonight to see whats wrong........I need coffee.....

-Cam

[vin63]

Only 10 miles, your engine probably never really got to operating temperature, and if it did, it didn't run there for long. This usually increases the amount of condensation in the crankcase, which increases the water content in the oil and lowers the PH level. Whether this is what helped to cause your current issues is difficult to tell or diagnose. I hope it's nothing serious.

[TheCougarine]

I'd be surprised if the oil weight was your issue. I guess if the motor wasn't getting up to operating temp ever then it could possibly do damage but I'm not sure of what kind. Is that a solid lifter cam? I know a lot of the 292 cams used to be. Thats an aggressive cam, depending on what exactly you did during the rebuild, that could cause problems with your valve train. I've seen the same thing discussed on some of the Chevelle forums.

[TJ's Chevy]

For an engine like that I would Never run a lower viscosity than 10w-30. If I was you I would run 15W-40 during the summer and 10w-30 in the winter. Both with high zinc levels. I would do an oil change and add a quart of lucas. If the lucas helps that just means you have some pesky lifters. 200 degrees is fine for that. Little hot yes as 180 is the optimum operating temp. I would throw in a thermostat. A 180 seems common for that engine.

[AntiqueAtHeart]

Originally Posted by vin63

Only 10 miles, your engine probably never really got to operating temperature, and if it did, it didn't run there for long. This usually increases the amount of condensation in the crankcase, which increases the water content in the oil and lowers the PH level. Whether this is what helped to cause your current issues is difficult to tell or diagnose. I hope it's nothing serious.

If the engine "warms up" at all it all goes to 140* max. Most of the time the gauge stays at the lowest mark of 100*. I hope it's nothing serious as well. Thank you for your reply Vin63.

[AntiqueAtHeart]

Originally Posted by TheCougarine

I'd be surprised if the oil weight was your issue. I guess if the motor wasn't getting up to operating temp ever then it could possibly do damage but I'm not sure of what kind. Is that a solid lifter cam? I know a lot of the 292 cams used to be. Thats an aggressive cam, depending on what exactly you did during the rebuild, that could cause problems with your valve train. I've seen the same thing discussed on some of the Chevelle forums.

I'm thinking it's the weight and the lack of engine temp as well. It has a hydraulic flat tappet 292 comp cam in it. I used Comps lifters, pushrods and rocker arms with the cam. I'm hoping the cam and lifters didn't get ate up. That's my worst nightmare but I'm being optimistic. Thanks for your reply TheCougarine.

[AntiqueAtHeart]

Originally Posted by TJ's Chevy

For an engine like that I would Never run a lower viscosity than 10w-30. If I was you I would run 15W-40 during the summer and 10w-30 in the winter. Both with high zinc levels. I would do an oil change and add a quart of lucas. If the lucas helps that just means you have some pesky lifters. 200 degrees is fine for that. Little hot yes as 180 is the optimum operating temp. I would throw in a thermostat. A 180 seems common for that engine.

I have a 180* thermostat on the shelf waiting on me......I think I should have made time to put it in....what are your views on Mobil 1 and Amsoil on the ZDDP levels? I've been running the STP brand ZDDP additive every oil change including initial break in. Maybe it's not enough? What kind of Lucas would you get? I've seen the Lucas brand ZDDP additive. Is this what you are talking about? How often have you used the 15w-40 and what have you used it in? I've thought about trying it but with my family saying just use 10w-30 for summer and that 15w-40 is too thick of an oil for 350 chevys, I've refrained from using it. Maybe that'll change. Thanks for your reply TJ.

[68gmsee]

Running without a thermostat is not recommended. Problems are carbon buildup, lower gas mileage, increased emission and engine wear. Also the engine never gets hot enough to evaporate moisture and creates internal condensation that is not good for the engine. Spend the 30 minutes needed to put in a thermostat of the recommended temperature.

[TJ's Chevy]

Originally Posted by AntiqueAtHeart

I have a 180* thermostat on the shelf waiting on me......I think I should have made time to put it in....what are your views on Mobil 1 and Amsoil on the ZDDP levels? I've been running the STP brand ZDDP additive every oil change including initial break in. Maybe it's not enough? What kind of Lucas would you get? I've seen the Lucas brand ZDDP additive. Is this what you are talking about? How often have you used the 15w-40 and what have you used it in? I've thought about trying it but with my family saying just use 10w-30 for summer and that 15w-40 is too thick of an oil for 350 chevys, I've refrained from using it. Maybe that'll change. Thanks for your reply TJ.

I would choose Amsoil over Mobile 1 anyday. Amsoil is a common brand of oil for flat tappet cams and comes with high zinc levels. Perfect for an aggressive cam like the one in your engine. I got the Lucas Engine Oil Stabilizer. In my engines I used Rotella 15w-40 year round with a zinc additive. I don't trust STP, but that is me. I prefer Lucas additive or Amsoil. Joe Gibbs oil is also a great choice. 15W-40 will Not hurt a 350 one bit. Cubic inch doesn't tell what viscosity you should use. In my rebuilt 292 I will run Straight 40 Joe Gibbs oil.

[storm9c1]

+1 on adding a thermostat. Not only does it help warm up in winter and allows engine to boil off condensation etc, but believe it or not, it helps it run cooler in summer by adding a metered restriction, slowing the coolant flow and allowing the coolant to soak up and carry away the heat evenly. If coolant circulates too fast, you end up with overheated hot spots in the heads that you won't see on a gauge. First symptom is burnt exhaust valves with high carbon build up (coking) in the exhaust ports. Check for that.

I don't think 5W-30 oil is hurting anything if your oil pressure is still good. But for anything with a flat tappet cam, I prefer 10W-30 or 10W-40. And anything with a roller cam gets 5W-30.

[vin63]

Originally Posted by AntiqueAtHeart

If the engine "warms up" at all it all goes to 140* max. Most of the time the gauge stays at the lowest mark of 100*. I hope it's nothing serious as well. Thank you for your reply Vin63.

Unfortunately, 140 degrees is not warm. Have you done valve lash since the noise started? Anything show up when you did?

[James the III]

Originally Posted by AntiqueAtHeart

Ive been driving my '66 long bed fleetside for about a year now. Ran it with 10w-30 and no thermostat in the summer and the temp never topped 200*. Now that its ~40* to 50* outside just about everyday, I switched to Mobil Super 5w-30 conventional oil and still have no thermostat due to lack of time to put one in. I've been driving everyday for about a month this way with an average of about 10 miles a day. The oil currently has 1700 miles on it and the engine is a 350 chevy with a Comp Cam 292 and stock valvetrain except springs and pushrods. I've put almost 4000 miles on it since rebuild.

It has now started to rattle badly like loose valvetrain and is missing on one cylinder. I'm pointing to the valvetrain......bad lifter.....

Did I kill my engine with thin conventional oil and no thermostat in winter?

I sure hope not. I'm going to try to pull it apart tonight to see whats wrong........I need coffee.....

-Cam

comp cams 292... stock valvetrain, but replaced the springs and push rods..
my vote is for a pressed in rocker stud (starting)pulling out..

Why are you going with no stat?? even in the summer.. you are giving away mpg and hp not running one..
you are also washing the cyl walls with fuel as it takes much longer to get up to temp.. shortning the engines life..

[Tom]

No thermostat is a no no in the summer time, even more so in the winter time. If your truck overheats with the thermostat installed you've got bigger problems.

[urmyboyblue]

I doubt that 5w-30 is an issue with your truck. No thermostat and 10 mile drives, as said, does not allow the engine to get up to temp- I would install one.

My experience with Comp cams is that the hydraulic flat tappets are very aggressive on the ramps. I would not be surprised if you flattened a lobe or pulled a rocker stud out if they are pressed in. Make sure you run plenty of ZDDP additive to your oil. I currently run 5w-40 full synthetic in my BBC and am surprised at how well it coats parts and doesn't run off like conventional oils- something you might want to look at.

I would suggest pulling the oil filter and cutting it open. Look for shiney particles- that will tell you if something is eating itself. Then pull the valve cover to look for any loose rocker arms.

[GASoline71]

Originally Posted by Tom

No thermostat is a no no in the summer time, even more so in the winter time. If your truck overheats with the thermostat installed you've got bigger problems.

Agree 100%!

Gary