safe to use 5w20 instead of 10w30

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Nov 24, 2008
Hello everyone, been a member for a little while first time posting. I drive a 1989 chevy camaro with the 305 and i am currently running quaker state horsepower full synthetic 10w30 and change it every 5k miles. The car uses very little oil but it uses some at startup from the valve guides and seals. It has 190,000 miles on it and i would like to experiment a little bit. I want to know if i can safely run a full synthetic 5w20 in place of the 10w30. I would like the car to last 300,000 miles. Thank you.
With a HM car like that that was originally spec'd for a 30wt oil it might be best to stick with the 30wt. Engines develop a wear pattern, and the thinner oil might possibly burn off faster than the 30wt oil. You can certainly try it and watch consumption. A buddy from this site uses 20wt oil in a HM Ford 3.0L engine and is using less oil with the 20wt than the 30wt. His engine was back-spec'd to a 20wt oil.

I like experiments, and would probably try it, just keep checking the oil level, if it uses too much oil you can always change back. JMO

I think it will smoke like a two stroke if you put a thinner oil in it with the bad valve guides. You actually might be better served by a 15W-40 HDEO like Delo in the summer and a 5W-30 passenger car synthetic in the winter.
Jacob- from my experience, a lighter viscosity seems travel past the guides even more when they are old. So I don't know if I would go the 5w route. Maybe some 5w/20 MaxLife or another HM oil would work better if you insisted on trying out a 5w/20. Better yet, I would try a 10w/30 HM oil. But it's your call of course and welcome to the board.
Personally i would not go thinner oil except for flushing only.
Because thinner oil that is burnt will add more deposit to your engine internals.

Since it only consumes a little oil, then drastic measure. eg. flush, open oil pan, may not be cost-effective because it may make it worse.

I agree with the HM oil usage that may help to condition the seal.
Would the thinner oil increase internal wear? it also has great oil pressure. at operating temperature it has 30psi at idle.
Try it and find out. I doubt you'll shorten the life of the engine. 10's of thousands of SBC owners flocked to M1 5w-20 back in the mid 70's and lived to tell about it.

I think you can handle it three and a half decades later.
Go 5w20 because you know you want to. It could go very well. If not, throw in some 10w40 at the next top up (or 20w50) - to get the visc back up.
Use a high mileage 5w30 in the winter and 10w30 in the summer... valvoline or pennzoil high mileage should do fine and maybe stop the oil seepage and oil burning or for sure slow it down.. High mileage oil works in a lot of cases where seals are the cause of the oil loss.. If it is the oil sender that may leak a bit then also replace it they are not expensive for that engine.. We have to replace them on over half the rebuilds we do.. With the proper carethat engine will go over 300,000 miles..
jacobl - crazyoildude has a pt - if you haven't tried an HM oil you should. I used pretty much all the HM oils (10w40) in a car I had with bad start-up smoke - almost eleminated it within one OCI - and kept it that way for about 8 years (till I sold it).
I can't see the logic here.

The engine has a lot of miles.

The 10w-30 is getting past the valve seals and guides.

It originally spec'd a 30wt and has not been back spec'd to a 20.

You have nothing to gain but you do have something to lose in the form of more oil consumption and potential wear from a high mileage bottom end in an engine that makes all of it's power down low in the rpm range.

I would say it's time for a 15w-40 or if you feel the need to experiment, something like Mobil One 0w-40 would make more sense.
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BuickGN - 15w40s and 0w40s will do very little for valve seal leak - any HM will do very much for valve seal leak - been there and done it.

If you really want a 5w20, then go with a 5w20 HM (I saw it, but can't remember who is making it). Not sure how that will work, but I'm fairly confident as to how a 10w40 HM will work for you.
I can't see the logic here.

There may be none. He wants to try it. I'm pretty sure that if a 5w-30 conventional was used from new that it experienced oil that sheared to a 20 grade ..probably for half of the engine's life. It lived through it.

Unless he intends to do a flat out run on the Bonneville salt flats, I can't see any one oci doing anything of merit to the "end of life" finish line for the engine.

I do somewhat agree with you. He may see more consumption..etc..etc. but going heavier is not what he wants to do.
I've tried shell rotella 15w40 and it ran good but smoked the same. I tried mobil 1 15w50 and hated it, car was sluggish. i want to see what a thinner oil will do. i am also curious about mobil 1 0w30.
You'll never know which grade is a good match for your particular engine until you try it.

My '00 MB E430 is spec'd with M1 0W40 or other heavy weight oil that meet ACAE A3-B3 (HTHS >= 3.5). It had M1 0W40 all its life until last summer it had PP 5W20, engine noise was down significant within few hundred miles, gas mileage improved and some other good things. After PP 5W20 I tried Delo 15W40, engine noise was back to before PP 5W20, gas mileage suffered. It has M1 0W20 now and the noise is down again.

I can not say that all MB E430 should use xW20 oil, but my particular car loves thinner oil.

Your mileage may varied, but you don't know if it will be better or worse until you try it.
I know it isn't the close to the same engine, but the 2.0 Neon engines recommend 10W30 or 5W30. I am running PP 5W20 with no issues. Switched at 87,300 miles or so. Been fine.
If anything, I'd go thicker, not thinner, in the Summertime.
But no way 5-20 in that engine.
4 1/2 more years and you can get antique license plates for it!
I'm with the recommendation for 15W-40: AMSOIL's AME 15W-40, to be exact. Can easily go 7,500 miles unless you are burning/leaking/using more than a quart (or 2) in this interval, IMHO.

Works great in my 420SEL!

Originally Posted By: ericthepig
BuickGN - 15w40s and 0w40s will do very little for valve seal leak - any HM will do very much for valve seal leak - been there and done it.

If you really want a 5w20, then go with a 5w20 HM (I saw it, but can't remember who is making it). Not sure how that will work, but I'm fairly confident as to how a 10w40 HM will work for you.

Wally World sells HM 5w20 in Pennz and Castrol - or valvoline maxlife
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