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Discussion Starter · #1 ·
I changed my oil today and after filling the Jeep up, I noticed somebody must have switched the oils in their places at the store. I was using 10W-30 as always but accidentally dumped in a quart of 10W40 and one of 20W-50. I can't see where this would do much harm but I'm far from an oil guru.
Any issues with this in SoCal or should I do another oil change? TIA

97 TJ 2.5 5 speed manual if it makes any difference
 

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Probably not gonna hurt anything. There are several debates on the internets about it, some say your engine will blow up and some say it won't. I think you will be ok.
 

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I changed my oil today and after filling the Jeep up, I noticed somebody must have switched the oils in their places at the store. I was using 10W-30 as always but accidentally dumped in a quart of 10W40 and one of 20W-50. I can't see where this would do much harm but I'm far from an oil guru.
Any issues with this in SoCal or should I do another oil change? TIA

97 TJ 2.5 5 speed manual if it makes any difference
In my opinion, not going to hurt anything. You should be fine. Back when I was a kid, I worked in a shop (that shall remain nameless) and they used to ask the customers what oil viscosity they wanted. Regardless of what they said, everyone got straight 20. That was the only oil the shop had and probably the cheapest oil money could buy.
 
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I dont see it hurting anything. For all we know maybe you just discovered the perfect cocktail for TJs :rofl:. Wouldn't run in there personally for more than 3000 miles though just as a precaution

I think it would be more of a concern if you had mixed something like 10W-40 (or heavier) and 0W-20 due to the extreme viscosity differences.
 

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Discussion Starter · #6 ·
Good enough for me guys. Thanks. Yeah, I might lose that TJ tick now. LOL.


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There is absolutely no debate from anyone who knows what they are talking about if mixing SAE oil viscosities will hurt anything or degrade the oil in any way. You can mix SAE rated oils and gear lubes to your heart's content.

For example, mixing 10W-30 50:50 with 5W-30 only makes it a 7.5W-30.
 

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And I thought I was the only one with the "TJ Tick"
I put off the inevitable by using thicker oil and a louder radio, I went to 15w/40 then to 20w/50....and turned up the radio
Running a 20W-50 is a great way to slow oil circulation when the engine is cold. Most engine damage is caused at the first startup of the day when oil isn't flowing quickly... especially with significantly higher than recommended viscosities like 20W-50. Sheesh.
 

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Oil threads are the car forum version of a food fight.

Back in the olden days when we premixed two stroke oil for our dirt bikes you could make jelly by mixing castor oil premix with mineral oil premix. So I am told. I never saw it actually happen but stashed it away in my memory. Never know when you might need a batch of poor man's napalm.

Drain your oil early if you get nervous and call it "cleaning your engine".
 

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Running a 20W-50 is a great way to slow oil circulation when the engine is cold. Most engine damage is caused at the first startup of the day when oil isn't flowing quickly... especially with significantly higher than recommended viscosities like 20W-50. Sheesh.
20w/50 is not for cold country, but If it wasn't from my success , I would agree with you
 

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20w/50 is not for cold country, but If it wasn't from my success , I would agree with you
Success meaning what? I've run nothing but the factory recommended 5W-30 and 10W-30 since those viscosities first became available and never had an engine problem. Even when it's not cold, higher viscosity oils flow more slowly... especially when the engine is being started for the first time of the day. Me? I want the oil to get throughout my engine as quickly as possible and even in warm weather, 20W (its weight before it is fully warmed up) is not going to flow as quickly then as a 5W or 10W will... as the factory recommends.

Personally, I wouldn't even consider running 20W-50 in my Jeep engine no matter where I lived. Especially since Jeep engineering doesn't recommend that heavy of a viscosity. :)
 

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Older engines have wear in the main and rod bearing, at least an additional .0005 to .001 clearance, I had a piston break at 318,000 miles, otherwise the engine would still be with us, the current engine, I bought with 125,000 and I have put another 40,000 with 20w/50 Castrol racing, my last long highway trip I averaged 20.9mpg

As I said before, if it wasn't for my success, I'd totally agree with you.

I just wish the D35's would last as long as these engines, I about just finishing off my 3rd.
 

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I changed my oil today and after filling the Jeep up, I noticed somebody must have switched the oils in their places at the store. I was using 10W-30 as always but accidentally dumped in a quart of 10W40 and one of 20W-50. I can't see where this would do much harm but I'm far from an oil guru.
Any issues with this in SoCal or should I do another oil change? TIA

97 TJ 2.5 5 speed manual if it makes any difference
You have made 15W40.
 

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Additive Clash is a real thing. So I am told. I have never actually seen it. If you mix oils at least mix them from the same line of oils.

Work took me to refineries in younger days. I saw different brands of oils all coming out of the same nozzle to fill oil bottles marked with different brands and different weights. I am almost sure there was some mixing going on. Refineries are not run by perfectionists. One of the dirtiest, nastiest, ugliest places I have seen on earth was at a refinery.
 

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You will be fine,especially if it is a one time thing. Dont lose any sleep over it.
 

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5 penzoil 5/20 and 1 valviline 5/30 ok?
Had the valvioline left from my car.


That Valvoline High Mileage Full Synth 5w30 has been noted as the best oil for the 4L.

As for mixing brands or viscosity, manufacturers don't recommend it due to potential comprises of the proprietary blend of anti wear agents and detergents.
I wouldn't be concerned about it however.

As for 20w50 in a 4L? Maybe in a super warm climate. Or maybe it proves how damn indestructible the Jeep 4.0 is.
And that theory of thick diesel oils to remedy lifter ticks and knocks is dead already. It doesn't make any sense.

As Jerry mentioned, lubrication during start up is most crucial and a lighter weight oil will move more freely to the valvetrain. Also film strength is a factor but we can only rely on studies to determine which oil on the market leaves the strongest film.


https://540ratblog.wordpress.com
 

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If you were on a trip, and you pulled into a gas station fueled and checked your oil and found the engine a quart low, what are you going to buy?
Chances are you won't see your brand, so you are going to try to match the weight as close as you can and ignore brand, or maybe you can buy your brand but have a different weight.

Dealerships and oil change shops around the country face this problem everyday when they run out of a specific oil during an oil change.
 
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