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10w40 Motor Oil?


Webb

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Hi I own an 2001 chevy K2500HD, 8.1L engine. My question is if 10W40 oil is too much? Ive always used 10w30, this time a tech at pepboys recomended I use 10w40. Said it was a summer oil. So I put the heavier oil in and took it for a test drive. I noticed my oil pressure gauge is about 20 psi higher than it normally is. usually gets up to about 40 psi now it goes right up to 60/70 psi. Thats about 3/4 of the way up the gauge instead of hoovering around the middle. Also noticed that my motor makes a deeper sound when revving. Not quite like a deisel just lower pitch sound than it had before.

 

So I went to autozone this time to ask them about it the guy there said I could blow my motor if the pressure is too high, and I should do another oil change back to w30 right away. So I went back to pepboys and told them my situation and they said it would be fine, its a summer oil. Only way I would blow my motor is if Im using it in the winter. Now Im really confused and worried. Im hopeing I dont have to bite the bullet and change it out again? Or will my engine be fine for the next 3,000 miles with this oil? Thanx in advance.

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10W40 is only necessary if you run your engine at extremely high temperatures. 30 weight is sufficient for regular use. 10/15W40 is usually the grade used in diesels. Stick with 10W30 or 5W30 for colder winters.

 

Edit: Sorry I missed your last question, will it damage anything? Very unlikely. Would I change it out asap if it was my truck? Probably not. Just run it for 3k then go back to 30 weight.

 

Edit #2: Does your oil pressure stay that high even when the oil is warmed up? Oil pressure is always highest at start up when the oil is cold/thick.

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I havent driven it too much, maybe a couple miles since the change. When it was warmed up seemed to go down to 40 psi when idling. It seemed the highest pressure when I was between 1,000 and 2,000 rpm's, maybe 75psi. Also it would drop a lil below 60 psi when I revved it to 3,000 rpm's wich seems counter intuitive. But thats what I can remember it doing last night. May go on a good sunday drive today and take some notes.

 

IDK maybe im being paranoid?

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Yeah I wouldn't worry too much about it. When it gets to be 15 -20 years old, some kid will be running 20W-50 in it to slow all the leaks.

 

I have a 24 year old Mercury that I parked one winter with straight 30W oil. Forgot about that the following spring. Motor made quite a racket for several seconds, (was about 40°F out) until the oil started moving. 160K miles on it & still running. Did the same thing with the '72 El Camino. As long as it's above 10°F your all set. If it's below that, it might tick for a couple seconds on cold starts.

 

My father knew a guy that was pouring 90 weight gear lube in his engine (a late 50's Buick) when he couldn't find any motor oil at a gas station in the middle of the Arizona desert, back in the 60's. He rode with the guy (was hitchhiking home from a naval base in San Diego) all the way to Chicago ... and the car ran fine! Better than nothin' I guess! :thumbs:

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I usually only run 40 weight oil in a vehicle with very high mileage, when the oil pressure is really low, Just to squeeze a few more months out of the vehicle before a rebuild or getting rid of it. So yeah if you have a tonne and a half miles on the truck...40 weight is probably a good idea.

GM vehicles run 30 weight oil in the middle east...and its balls hot over there.

and I am pretty sure it says in your owners manual not to run 40 or 50 weight oil in your engine.

 

Remember the temp of your engine is controlled by your cooling system...maybe you should pay more attention to it than the temp of your oil. Weather its 70* outside or 100*...your engine is going to run at 198* if the cooling system is working properly.

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It has about 120,000 miles on it. Not sure if youd consider that high? The temp coolant temp seems unafected by the oil change. Mostly worried about what the guy at autozone said, that it may be like having too much oil and I may throw some kinda rod or object cant remember? Thanx for the info guys.

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It has about 120,000 miles on it. Not sure if youd consider that high? The temp coolant temp seems unafected by the oil change. Mostly worried about what the guy at autozone said, that it may be like having too much oil and I may throw some kinda rod or object cant remember? Thanx for the info guys.

Oh it wont do anything like that...it would at worst build too much pressure and end up blowing a seal out...but if your only making 40PSI, I think your fine.

120K isn't really high...I was thinking 200K+ and starting to make weird noises, That's what would make me run 40weight. Other than that I would use the recommended weight oil.

 

I hope the guy your listening too at these places at least has some grey hairs, If your listening to some 20y/o car guru...STOP IT

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Oh it wont do anything like that...it would at worst build too much pressure and end up blowing a seal out...but if your only making 40PSI, I think your fine.

120K isn't really high...I was thinking 200K+ and starting to make weird noises, That's what would make me run 40weight. Other than that I would use the recommended weight oil.

 

I hope the guy your listening too at these places at least has some grey hairs, If your listening to some 20y/o car guru...STOP IT

 

I cannot think of a seal in the engine that it would blow out. There is a function in the oil pump to limit oil pressure. Sounds like the person that told him too much pressure would blow the engine is also one of those that says an extra quart of oil will blow seals.

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a tech at pepboys recomended I use 10w40. Said it was a summer oil.

:happysad: summer in NH, sorry i had to. how hot dose it get, about 85*? 10W-30 will be fine even with the mileage you have. the reason i :lurk: is summer time here has a temp of 120*+ and a road surface of 140*+ and i still use 5W-30 with no issues at all. BTW..NH is the prettiest state that I've ever been to.. :thumbs:

 

good luck

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Oh it wont do anything like that...it would at worst build too much pressure and end up blowing a seal out...but if your only making 40PSI, I think your fine.

120K isn't really high...I was thinking 200K+ and starting to make weird noises, That's what would make me run 40weight. Other than that I would use the recommended weight oil.

 

I hope the guy your listening too at these places at least has some grey hairs, If your listening to some 20y/o car guru...STOP IT

 

I cannot think of a seal in the engine that it would blow out. There is a function in the oil pump to limit oil pressure. Sounds like the person that told him too much pressure would blow the engine is also one of those that says an extra quart of oil will blow seals.

 

Ahhh...rear main seal is one that comes to mind. You've never seen a seal blow out on an engine??? Also, the oil pump is not the only place pressure is made. oil squeezed through the cam and crank bearings also contribute to internal engine or crank case pressure. It will find the quickest way out, usually the PCV line, but if a blockage occurs or the PCV outlet is too small for the pressure to escape, it will pop out of a weak seal.

 

Also, an extra quart of oil is not going to do much, except maybe cause some parasitic drag if the crank is forced to rotate through oil. I don't think an extra quart would be enough though.

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